reptiles & amphibians - internet center for wildlife damage

REPTILES, AMPHIBIANS, ETC.

F-1 Alligators Allan R. Woodward and Dennis N. David

F-7 Crayfish James F. Fowler, Wendell Lorio, and Greg Lutz

F-9 Frogs and Toads Paul E. Moler

F-13 Salamanders James L. Byford

F-15 Snakes, Nonpoisonous James L. Byford

F-21 Rattlesnakes Walter E. Howard

F-27 Turtles James F. Fowler and Jimmy L. Avery

ALLIGATORSAllan R. WoodwardAlligator Research BiologistFlorida Game and Fresh Water Fish

CommissionGainesville, Florida 32601

Dennis N. DavidAlligator Management Section LeaderFlorida Game and Fresh Water Fish

CommissionGainesville, Florida 32601

Damage Prevention andControl MethodsExclusion

Bulkheads along edges of lakes andwaterways.

Wire mesh fences.

Habitat Modification

Minimize emergent vegetation.

Drain ponds and borrow pits whereappropriate and permitted.

Frightening

Prodding or other harassment canincrease wariness.

Hunting pressure increases warinessand avoidance of people.

Repellents

None are registered.

Toxicants


Fumigants


Trapping

Baited hooks and trip-snare traps aremost effective.

Shooting

Hunt during the day or night withrifles or crossbows.

Other Methods

Hunt with detachable-head harpoonsor handheld, breakaway polesnares.

Capture with snatch hooks or tongs.

Fig. 1. American alligator,Alligator mississippiensis

PREVENTION AND CONTROL OF WILDL

Cooperative Extension DivisionInstitute of Agriculture and Natural ResourceUniversity of Nebraska - Lincoln

United States Department of AgricultureAnimal and Plant Health Inspection ServiceAnimal Damage Control

Great Plains Agricultural CouncilWildlife Committee

Identification

The American alligator (Alligatormississippiensis, Fig. 1) is the most com-mon of two crocodilians native to theUnited States and is one of 22 crocodil-ian species worldwide. The othernative crocodilian is the Americancrocodile (Crocodylus acutus). Caimans(Caiman spp.), imported from Centraland South America, are occasionallyreleased in the United States and cansurvive and reproduce in Florida. TheAmerican alligator is distinguishedfrom the American crocodile andcaiman by its more rounded snout andblack and yellow-white coloration.American crocodiles and caimans areolive-brown in color and have morepointed snouts. American alligatorsand crocodiles are similar in physicalsize, whereas caimans are 40% smaller.

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Range

The American alligator is found inwetlands throughout the coastal plainof the southeastern United States.Viable alligator populations are foundin Texas, Oklahoma, Arkansas, Louisi-ana, Mississippi, Alabama, Florida,Georgia, South Carolina, and NorthCarolina. The northern range is limitedby low winter temperatures. Alligatorsare rarely found south of the RioGrande drainage. Alligators preferfresh water but also inhabit brackishwater and occasionally venture intosalt water. American crocodiles arescarce and, in the United States, areonly found in the warmer coastalwaters of Florida, south of Tampa andMiami. Caimans rarely survive win-ters north of central Florida and repro-duce only in southernmost Florida.

Habitat

Alligators can be found in almost anytype of fresh water, but populationdensities are greatest in wetlands withan abundant food supply and adjacentmarsh habitat for nesting. In Texas,Louisiana, and South Carolina, thehighest densities are found in highlyproductive coastal impoundments. InFlorida, highest densities occur innutrient-enriched lakes and marshes.Coastal and inland marshes maintainthe highest alligator densities in Geor-gia, Alabama, and Mississippi. Alliga-tors commonly inhabit urban wetlands(canals, lagoons, ponds, impound-ments, and streams) throughout theirrange.

Food Habits

Alligators are exclusively carnivorousand prey upon whatever creatures aremost available. Juvenile alligators (lessthan 4 feet [1.2 m]) eat crustaceans,snails, and small fish; subadults (4 to 6feet [1.2 to 1.8 m]) eat mostly fish, crus-taceans, small mammals, and birds;and adults (greater than 6 feet [1.8 m])eat fish, mammals, turtles, birds, andother alligators. Diets are range-depen-dent; in Louisiana coastal marshes,adult alligators feed primarily onnutria (Myocastor coypus), whereas inFlorida and northern Louisiana, rough

fish and turtles comprise most of thediet. Recent studies in Florida andLouisiana indicate that cannibalism iscommon among alligators. Alligatorsreadily take domestic dogs and cats. Inrural areas, larger alligators takecalves, foals, goats, hogs, domesticwaterfowl, and occasionally, full-grown cattle and horses.

General Biology,Reproduction, andBehavior

Alligators are ectothermic — they relyon external sources of heat to maintainbody temperature. They are mostactive at warmer temperatures andprefer 82o to 92o F (28o to 33o C). Theystop feeding when ambient tempera-ture drops below 70o F (21o C) andbecome dormant below 55o F (13o C).

Alligators are among the largest ani-mals in North America. Males canattain a size of more than 14 feet (4.3m) and 1,000 pounds (473 kg). Femalescan exceed 10 feet (3.1 m) and 250pounds (116 kg). Alligators of bothsexes become sexually mature whenthey attain a length of 6 to 7 feet (1.8 to2.1 m), but their full reproductivecapacity is not realized until femalesand males are at least 7 feet (2.1 m)and 8 feet (2.4 m) long, respectively.

Alligators begin courtship in Aprilthroughout most of their range andbreed in late May and early June.Females lay a single clutch of 30 to 50eggs in a mound of vegetation fromearly June to mid-July. Nests averageabout 2 feet (0.6 m) in height and 5 feet(1.5 m) in diameter. Nests are con-structed of the predominant surround-ing vegetation, which is commonlycordgrass (Spartina spp.), sawgrass(Cladium jamaicense), cattail (Typhaspp.), giant reed (Phragmytes spp.),other marsh grasses, peat, pineneedles, and/or soil. Females tendtheir nests and sometimes defendthem against intruders, includinghumans. Eggs normally take 65 daysto complete incubation. In late Augustto early September, 9 to 10-inch (23 to25-cm) hatchlings are liberated fromthe nest by the female. She may defend

her hatchlings against intruders andstay with them for up to 1 year, butgradually loses her affinity for them asthe next breeding season approaches.

Growth rates of alligators are variableand dependent on diet, temperature,and sex. Alligators take 7 to 10 years toreach 6 feet (1.8 m) in Louisiana, 9 to14 years in Florida, and up to 16 yearsin North Carolina. When maintainedon farms under ideal temperature andnutrition, alligators can reach a lengthof 6 feet (1.8 m) in 3 years.

Alligators are not normally aggressivetoward humans, but aberrant behavioroccasionally occurs. Alligators can andwill attack humans and cause seriousinjury or death. Most attacks are char-acterized by a single bite and releasewith resulting puncture wounds.Single bites are usually made bysmaller alligators (less than 8 feet [2.4m]) and result in an immediate release,possibly because they were unsure oftheir intended prey. One-third of theattacks, however, involve repeatedbites, major injury, and sometimesdeath. Serious and repeated attacks arenormally made by alligators greaterthan 8 feet in length and are mostlikely the result of chase and feedingbehavior. Unprovoked attacks by alli-gators smaller than 5 feet (1.5 m) inlength are rare.

Contrary to popular belief, few attackscan be attributed to wounded or terri-torial alligators or females defendingtheir nests or young. Necropsies of alli-gators that have attacked humans haveshown that most are healthy and well-nourished. It is unlikely that alligatorattacks are related to territorialdefense. When defending a territory,alligators display, vocalize, and nor-mally approach on the surface of thewater where they can be more intimi-dating. In most serious alligatorattacks, victims were unaware of thealligator prior to the attack. Femalealligators frequently defend their nestand young, but there have been noconfirmed reports of humans beingbitten by protective females. Broodingfemales typically try to intimidateintruders by displaying and hissingbefore attacking.

Alligators quickly become conditionedto humans, especially when food is in-volved. Feeding-habituated alligatorslose their fear of humans and can bedangerous to unsuspecting humans,especially children. Many aggressiveor “fearless” alligators have to be re-moved each year following feeding byhumans. Ponds and waterways at golfcourses and high-density housing cre-ate a similar problem when alligatorsbecome accustomed to living nearpeople.

Damage and DamageIdentification

Damage by alligators is usually limitedto injuries or death to humans ordomestic animals. Most alligator bitesoccur in Florida, which has document-ed approximately 140 unprovokedattacks from 1972 to 1991, or about 7per year. Since 1972, 5 deaths havebeen positively attributed to alligators.Historically, nonfatal attacks have alsobeen documented in South Carolina(8), Louisiana (2), Texas (1), Georgia(1), and Alabama (1).

Alligators inflict damage with theirsharp, cone-shaped teeth and powerfuljaws. Bites are characterized by punc-ture wounds and/or torn flesh. Alliga-tors, like other crocodilians that takelarge prey, prefer to seize an append-age and twist it off by spinning. Manyserious injuries have involved badlydamaged and broken arms on humansand legs on animals. Sometimes alliga-tors bite or eat previously drownedpersons. Coroners can usually deter-mine whether a person drownedbefore or after being bitten. Stories ofalligators breaking the legs of full-grown men with their tails areunfounded.

Alligators sometimes excavate exten-sive burrows or dens for refuges fromcold temperatures, drought, andpredators (other alligators and hu-mans). Burrowing by alligators candamage dikes in impoundments.

Legal Status

The American alligator is federallyclassified as “threatened due to simi-

larity of appearance” to otherendangered and threatened crocodil-ians. This provides federal protectionfor alligators but allows state-approved management and controlprograms. Alligators can be legallytaken only by individuals with properlicenses or permits. Florida, Louisiana,Georgia, South Carolina, and Texashave problem or nuisance alligatorcontrol programs that allow permittedhunters to kill or facilitate the removalof nuisance alligators. Other statesuse state wildlife officials to removeproblem animals.


Alligators are most dangerous in wateror at the water’s edge. They occasion-ally make overland forays in search ofnew habitat, mates, or prey. Concreteor wooden bulkheads that are a mini-mum of 3 feet (1 m) above the highwater mark will repel alligators alongwaterways and lakes. Alligators havebeen documented to climb 5-foot (1.5-m) chain-link fences to get at dogs.Fences at least 5 feet high with 4-inch(10-cm) mesh will effectively excludelarger alligators if the top of the fenceis angled outward.


Elimination of wetlands will eradicatealligators because they depend onwater for cover, food, and temperatureregulation. Most modifications of wet-lands, however, are unlawful andwould adversely affect other wildlife.Elimination of emergent vegetationcan reduce alligator densities byreducing cover. Check with appropri-ate conservation authorities beforemodifying any wetlands.

Frightening

Aversive conditioning using sticks toprod “tame” alligators and rough han-dling of captured alligators have beenattempted in several areas with limitedsuccess. Hunting pressure appears tobe the most effective means of increas-ing alligator wariness and may be re-sponsible for limiting the incidence of

alligator attacks in Florida, despite in-creasing human and alligator popula-tions. The historically low attack ratein Louisiana is attributed to a historyof intense hunting.

Repellents


Toxicants


Trapping

Alligators can be readily trapped be-cause they are attracted to baits. Abaited hook is the simplest methodand is used in Louisiana as a generalharvest method and in Florida toremove nuisance alligators. Hooks arerigged by embedding a large fish hook(12/0 forged) in bait (nutria, fish, beeflungs, and chicken are popular) andsuspended from a tree limb or poleabout 2 feet (0.6 m) above the surfaceof the water. The bait should be setcloser to the water to catch smaller alli-gators. To increase success, baitedhooks should be set in the evening andleft overnight during the primary feed-ing time of alligators. Once swallowed,the hook lodges in the alligator’s stom-ach and the alligator is retrieved withthe attached rope. This method can killor otherwise injure alligators and is notsuitable for alligators that are to betranslocated. Hooked alligators aremost effectively killed by a shot to thebrain with a small caliber (.22) rifle.Powerheads (“bangsticks”) can also beused to kill alligators, but should onlybe used with the barrel under waterand according to manufacturer recom-mendations.

Trip-snare traps (Fig. 2) are more com-plicated and somewhat less effectivethan are set hooks but do not injure orkill alligators. An alligator is attractedto the bait and, because of the place-ment of the guide boards, is forced toenter from the end of the trap with thesnare. The alligator puts its headthrough the self-locking snare (No. 3,72-inch [1.84-m]; see Supplies andMaterials), seizes the bait, and releasesthe trigger mechanism as it pulls thebait. The surgical tubing contracts andlocks the snare on the alligator. These

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INSERT

6"

See insert

32" surgicaltubing stretchedto 80" when snareis set

8"

KleflockNo. 2 SnareFragile

Twig

20"

WATEREDGE

SurgicalTubing

WATERLINE

Fig. 2. Alligator trip-snare trap.

Smooth TopNotch

3/16" x 3" woodendowel with eyeletinserted into surgi-cal tubing

8 P common naildriven through 1" x 2"upright and excesstrimmed to 3/4"

traps can be modified as floating sets.A variation of the trip-snare trap canbe set on alligator trails and rigged totrip by the weight of the alligator (seeMazzotti and Brandt 1988).

Wire box traps have been used effec-tively to trap alligators. Heavy netshave been used with limited success tocapture alligators and crocodiles atbasking sites.

Translocation

Translocation of problem alligatorswas practiced extensively during the1970s with limited success. Alligators,especially larger ones, tended to returnto their original capture sites afterbeing moved. These alligators not onlycaused problems during their returntrip but frequently required subse-quent capture and translocation.Translocation is not recommendedunless areas with depleted alligatorpopulations are available for release ofproblem animals.

Shooting

Next to baited hooks, shooting is prob-ably the most effective means ofremoving alligators. Alligators can beshot during the day or at night, andshould be shot in the brain case with asufficiently powerful rifle (.243 caliberand larger) for an efficient andhumane kill. Firearms, however, pre-sent public safety problems in mostnuisance alligator settings. Further-more, alligators sink almost immedi-ately after dying and may be difficultto recover (by gaffs or snatch hooks) inareas with currents or dense submer-gent plants. This method may makeconfirmation of a kill difficult and maycompromise the commercial value ofthe alligator. Crossbows with linesattached to barbed bolts work fairlywell at short distances but should onlybe used to kill alligators.

Other Methods

Detachable-head harpoons (Fig. 3a, b)with attached lines have been used ef-fectively to harvest nuisance alligators.A harpoon assembly (Fig. 3a) is at-tached to a 10- to 12-foot (3- to 3.5-m)wooden pole. The harpoon is thrust at

the alligator and, after the tip pene-trates the skin, withdrawn, leaving thetip embedded under the alligator’sskin (Fig. 3b). As tension is placed onthe retrieval line, the off-center attach-ment location of the cable causes thetip to rotate into a position parallel tothe skin of the alligator, providing asecure attachment to the alligator. Har-poons are less effective than firearms,but the attached line helps to ensurethe recovery of the alligator.

Snatch hooks are weighted multitinehooks on fishing line that can be castover an alligator’s back and embeddedin its skin. The size of hooks and theline strength should be suited to the

size of the alligator; small alligatorscan be caught with standard light fish-ing gear while large alligators require10/0 hooks, a 100-pound test line, anda heavy-duty fishing rod. Heavy hookswith nylon line can be hand-cast forlarger alligators. After the hook pen-etrates the alligator’s skin, the linemust be kept tight to prevent the hookfrom falling out. Alligators frequentlyroll after being snagged and becomeentangled in the line. This entangle-ment permits a more effective recov-ery. Snatch hooks work well duringthe day and at night, provided thatvegetation is minimal.

Handheld poles with self-locking

Peg(stainless steel)Tip

(stainless steel)

Base(aluminum) Tube

(copper)

Cable(stainless steel)

a

bSkin

Muscle

Nylonrope

Duct tape(1/2")

Fig. 4. Break-away snare.

Locking snare (No. 3)

Fig. 3. (a) Detachable-head harpoon; (b) Rotation of harpoon tip after penetration.

snares (sizes No. 2 and 3; Fig. 4) can beused effectively to capture unwaryalligators at night. For smaller (lessthan 6 feet [1.8 m]) alligators, snarescan be affixed to a pole with a hoseclamp. For adult alligators, snaresshould be rigged to “break away”from the pole by attaching the snare tothe pole with thin (1/2-inch [1-cm]wide) duct tape (Fig. 4). The tape orclamps allow the snare to be maneu-vered and are designed to release afterthe snare is locked. Carefully place thesnare around the alligator’s neck, thenjerk the pole and/or retrieval line toset the locking snare. A nylon retrievalrope should always be fastened to thesnare and the rope secured to a boat orother heavy object.

For alligators less than 6 feet (1.8 m)long, commercially available catchpoles (Fig. 5; see Supplies andMaterials) can be used. Snake tongs(Fig. 6, see Supplies and Materials)are effective for catching alligators lessthan 2 feet (0.6 m) long.

Avoidance

Measures can be taken to avoid con-frontations with alligators and sub-stantially reduce the probability ofattacks. Avoid swimming or partici-pating in water activities in areas withlarge alligators. Avoid water activitiesat dusk and at night during thewarmer months when alligators aremost active. Alligators can quicklysurge at least 5 feet (1.5 m) onto theshore to seize prey, so care should betaken when at the water’s edge. Donot feed alligators. Avoid approachingnests and capturing young (<2 feet[0.6 m]) alligators.

Economics of Damage andControl

Alligators can cause injuries and deathto humans, livestock, and pets. All alli-gator bites require medical treatmentand serious bites may require hospital-ization. Infections can result from alli-gator bites, particularly from theAeromonas spp. bacteria.

Lawsuits that arise from findings ofnegligence on the part of a private

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Fig. 5. Commercial catch pole.

Fig. 6. Snake tongs.

owner or governmental agencyresponsible for an attack site can leadto significant economic liability.

In Florida, approximately 15% of thealligator complaints are due to fear ofpet losses and, to a lesser extent, live-stock losses. Losses of livestock otherthan domestic waterfowl, however,are uncommon and difficult to verify.Levees damaged by alligator burrowsor dens may require repair.

Alligators are valuable for their skinand meat. An average-sized nuisancealligator typically yields 8 feet (2.4 m)of skin and 30 pounds (13.5 kg) ofboneless meat with a wholesale value

of $390 (at $30 per foot for skins and $5per pound for meat). Other productssuch as skulls, teeth, fat, and organscan be sold, but account for less than10% of the value of an alligator. Nui-sance alligator control programs inseveral states use the sale of alligatorskins to offset costs of removal andadministration.

Florida has the most pressing nuisancealligator problem and currently har-vests about 4,000 alligators per year.Nuisance alligator harvests also occurin Louisiana (600), Georgia (400),South Carolina (250), and Texas (50).

Acknowledgments

We thank William Brownlee, Texas Parks andWildlife Department; Ted Joanen, LouisianaDepartment of Wildlife and Fisheries; SteveRuckel, Georgia Department of NaturalResources; Thomas Swayngham, South CarolinaDepartment of Wildlife and Marine Resources;and Paul Moler and Michael Jennings, FloridaGame and Fresh Water Fish Commission forproviding information on their respective statesand for reviewing this chapter. We also thankThomas Murphy and Philip Wilkinson, SouthCarolina Department of Wildlife and MarineResources, for providing diagrams of the trip-snare trap.

For AdditionalInformation

Delany, M. F., A. R. Woodward, and I. H.Kochel. 1988. Nuisance alligator food habitsin Florida. Florida Field Nat. 16:90-96.

Hines, T. C., and K. D. Keenlyne. 1976. Alligatorattacks on humans in Florida. Proc. Ann.Conf. Southeast. Assoc. Fish Wildl. Agencies30:358-361.

Hines, T. C., and A. R. Woodward. 1980.Nuisance alligator control in Florida. Wildl.Soc. Bull. 8:234-241.

Jennings, M. L., A. R. Woodward, and D. N.David. 1989. Florida’s nuisance alligatorcontrol program. Proc. Eastern Wildl.Damage Control Conf. 4:29-36.

Joanen, T., and L. McNease. 1987. Themanagement of alligators in Louisiana,U.S.A. Pages 33-42 in G. J. W. Webb, S. C.Manolis, and P. J. Whitehead, eds. Wildlifemanagement: crocodiles and alligators.Surrey Beatty and Sons Pty. Ltd., ChippingNorton, NSW, Australia.

Mazzotti, F. J., and L. A. Brandt. 1988. A methodof live-trapping wary crocodiles. Herpetol.Rev. 19:40-41.

Murphy, T., P. Wilkinson, J. Coker, and M.Hudson. 1983. The alligator trip snare: a livecapture method. South Carolina Wildl. andMarine Resour. Dep., Columbia. (unpub.brochure).

Thompson, B. C., L. A. Johnson, D. S. Lobpries,and K. L. Brown. 1986. Capabilities ofhunters to shoot and retrieve free-swimmingalligators. Proc. Ann. Conf. Southeast. Assoc.Fish Wildl. Agencies 40:342-348.

EditorsScott E. HygnstromRobert M. TimmGary E. Larson

CRAYFISHJames F. FowlerWildlife SpecialistLouisiana Cooperative

Extension ServiceLouisiana State University

Agricultural CenterBaton Rouge, Louisiana 70803

Wendell LorioAquaculture SpecialistLouisiana Cooperative


Agricultural CenterBaton Rouge, LA 70803

Greg LutzAquaculture SpecialistLouisiana Cooperative


Agricultural CenterBaton Rouge, LA 70803

Damage Prevention andControl Methods

Exclusion

Not practical.

Cultural Methods

Deep tillage destroys burrows andgenerally results in lowerpopulations.

Drainage of rice irrigation systems andfields during fall and winter monthsreduces populations.

Repellents


Toxicants

None are registered. Check individualstate regulations for Special LocalNeeds registrations 24(c).

Approved turf insecticides used forinsect pest control will also controlcrayfish in lawn and turf areas.

Fumigants

None are registered. Check stateregulations for Special Local Needsregistrations 24(c).

Trapping

Not effective in eliminatingpopulations. May be used incapturing crayfish for bait or food.

Fig. 1. Crayfish

PREVENTION AND CONTROL OF WILDLI

Cooperative Extension DivisionInstitute of Agriculture and Natural ResourcesUniversity of Nebraska - Lincoln



Identification, Range, andBiology

Crayfish, also called crawfish,crawcrab, crab, stonecrab, crawdad,creekcrab, and other local names, arenative to fresh waters on all continentsexcept Africa, where they have beenwidely introduced. There are over 400species in the family Astacidae world-wide, and approximately 300 speciesin the United States. In size, shape, andcolor, the variation is extremely wideamong species. The detailed life histo-ries and habits of all species of crayfishare beyond the scope of this handbook.

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Crayfish are economically important ina number of states for use as fish baitand for human consumption. In Loui-siana, the crayfish is a major economiccrop and comprises the second largestaquaculture industry in NorthAmerica. Over 130,000 acres (56,000ha) are devoted solely to crayfishculture.

Damage

Most damage associated with crayfishis the result of crayfish burrowing inhome lawns. Burrows created byburrowing species of crayfish are dam-aging to turf areas and may be hazard-ous to mowing machinery. Newlyplanted rice fields may be damaged byforaging crayfish where local popula-tions are high.

Crayfish populations in commercialbaitfish ponds can reduce reproduc-tion by feeding on the eggs of thebaitfish as they are deposited onspawning mats. During pond harvest,crayfish caught in the nets injure anddestroy baitfish as they are being har-vested for market.

Unwanted populations of crayfishhave been established in the wildbecause of the release of bait crayfish.Some populations have reachedextremely high levels. Crayfish canreduce game fish populations by prey-ing on eggs and fry. They also candegrade habitat by destroying aquaticvegetation.

Legal Status

Crayfish may be protected by law insome states. Harvest of crayfish mayalso be regulated by state wildlife con-servation agencies. In areas wheredamage occurs, control measures aregenerally unrestricted. Check withyour local agricultural or wildlifeauthorities before initiating control.Unwanted populations of crayfishhave resulted in regulations againstthe use of crayfish as bait in somenorthern lakes.


Cultural Methods

Deep cultivation helps reduce burrow-ing crayfish populations in rice fieldsand other grain crops. Drainage of riceirrigation canals and fallow fields dur-ing fall and winter is also helpful inreducing crayfish populations in theseareas.

High populations of crayfish aregenerally associated with years of highrainfall. Unseasonably dry weatherconditions usually reduce crayfishnumbers.

Rapid drainage of baitfish ponds dur-ing early spring helps eliminate cray-fish by exposing them to predatorsbefore burrowing activities begin.Principal predators include snakes,racoons, mink, otter, skunks, bass,catfish, ibis, and herons.

Toxicants

There are no General Use Pesticidesregistered for crayfish control. In somestates, however, Special Local Needsregistration under section 24(c) ofFIFRA have been established for cer-tain insecticides for burrow treatment.

Toxicants, where legal, may be used atany time of the year when crayfish areactive, but best results are obtained inearly fall when adults are in their bur-rows. To be effective, applications oftoxic chemicals must reach the waterin the burrows. Additional treatmentsmay be necessary where burrows indikes or dams open at the bottom intoa pond or stream.

Fumigants

None are federally registered for cray-fish control. Check with your localwildlife or agricultural agency forSpecial Local Needs registrations.

Trapping

Wire cage traps, baited with fish,chicken, or other meat can be used tocapture crayfish, but they are not cost-effective in damage control situations.

Acknowledgments

Figure 1 by Emily Oseas Routman.


Hobbs, H. H., Jr. 1972. Crayfishes (Astacidae) ofNorth and middle America. IdentificationManual No. 9, Biota of FreshwaterEcosystems, US Environ. Prot. Agency.Washington, DC. 173 pp.

Momot, W. T., G. Howing, and P. D. Jones. 1978.The dynamics of crayfish and their role inecosystems. Am. Midl. Nat. 99:10-35.

Pennak, R. W. 1978. Freshwater invertebrates ofthe United States, 2d ed. John Wiley andSons, New York. 803 pp.

Pflieger, W. L. 1987. An introduction to thecrayfish of Missouri. Missouri Dep. Conserv.Jefferson City. 16 pp.

Williams, A. B., and A. B. Leonard. 1952. Thecrayfishes of Kansas. Univ. Kansas, Sci. Bull.34:961-1012.


F-9

FROGS AND TOADSPaul E. MolerWildlife BiologistFlorida Game and Fresh Water Fish

CommissionWildlife Research LaboratoryGainesville, Florida 32601

Trapping

Funnel traps.

Capture

Capture by hand or gig at night.

Egg masses may be removed with afine-meshed net.

Shooting

Allowed in some states, but often notsafe in areas requiring control.Some states permit shooting onlyduring daylight hours.


Around hatchery ponds, keep vegeta-tion closely mown and removeemergent vegetation and othertypes of cover.

Frightening

Not applicable.

Repellents


Toxicants


Fumigants



Exclusion

Seal all openings 3/16 inch (0.5 cm) orlarger to exclude frogs.

A frogproof fence can be used fornonclimbing species, but will be in-effective against treefrogs and a fewrelated species.

On fish farms, mesh tenting overponds will serve to exclude frogs aswell as birds and other predators.

Fig. 1. Great Plains toad, Bufo cognatus

PREVENTION AND CONTROL OF WILDLIFE DAMAGE — 1994




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Identification

Frogs and toads are amphibians withfour legs and no tail. They may haveskin that is smooth and moist or dryand warty, but they have no scales orclaws. The front legs are short, but thehind legs are muscular and elongatedfor hopping or jumping. The populardistinction between frogs and toads issomewhat artificial; basically, toadsare a particular group of frogs.Throughout this chapter, the term frogwill be used to include toads. NorthAmerican frogs range in body sizefrom the 11/16-inch (1.7-cm) littlegrass frog to the 8-inch (20-cm) bull-frog.

Range

At least 85 species of frogs are nativeto the United States, and there arethree well-established exotic species.There is no part of the country that isnot home to at least a few species.

Habitat

Frogs occur in almost all nonmarinehabitats. “True” frogs (genus Rana)and treefrogs predominate in the morehumid east. In the drier Great Plainsand western regions, toads andspadefoots are typically more numer-ous. Whereas some species are seldomfound far from permanent water,others return to water only seasonallyto breed. Some desert species spendmost of their time beneath ground,venturing to the surface only followingrains.

Food Habits

Most frogs have a two-phased lifecycle, including an aquatic larval form(tadpole) and a terrestrial or semi-aquatic adult form. Tadpoles are pri-marily herbivorous, feeding on algaeand decaying organic matter. Adults,on the other hand, are carnivorous,consuming almost any prey that can beoverpowered. Although the diet con-sists primarily of insects, crayfish, andother invertebrates, larger frogs occa-sionally take snakes, other frogs, fish,

mice, and small birds. In natural habi-tats, fish usually comprise less than 5%of the diet of the bullfrog. On fishfarms, as many as 30% of bullfrogshave been found to contain fish.


Although some species spend most oftheir adult lives away from water,most frogs native to North Americamust return to water to lay eggs. Somespecies breed during the cooler winterand spring months, whereas othersbreed during the warmer months. Fol-lowing rain, males begin calling frombreeding sites. Each species has itsown distinctive call, and femalesrespond only to the calls of their ownspecies. Several recordings of frog callsare available, and four are listed at theend of this chapter.

Eggs are fertilized by the male as theyare released by the female. Hatchingoccurs a few days later. The aquatictadpole stage may last as little as 2 to 3weeks in some species of spadefoots oras long as 2 years in some northernpopulations of bullfrogs.

Frogs are typically most active atnight. Some species aggregate aroundartificial lights and feed on the insectsattracted there. Frogs are an importantcomponent of the vertebrate foodchain and are consumed by a varietyof predators, including fish, snakes,turtles, wading birds, raptors, skunks,and raccoons. Individuals of manyspecies may live 12 to 15 years, but lifeexpectancy is much shorter in thewild.

Damage

The greatest potential for economicdamage is at fish farms and hatcheries.Tadpoles compete for food intendedfor fish, and adult bullfrogs may actu-ally feed on the fish. Losses are said tobe high at some fish farms. One studysuggested that the mere presence ofhigh densities of tadpoles retardedreproduction of fish. Although thebullfrog is native to most of the easternUnited States, its introduction to por-

tions of the west has seriously affectedsome native species. In at least somecases, these introductions may haveresulted from the unintentional releaseof tadpoles during fish-stocking pro-grams. Considerable labor is requiredto separate tadpoles from loads of fry.

Only in rare instances do frogs causeany significant damage. Some species(toads, for example) produce skinsecretions that are toxic if ingested.This does not normally present a prob-lem for people, and pets usually learnto avoid such frogs. A few species(giant toad, Colorado River toad) pro-duce especially copious or toxic secre-tions, and there have been cases inwhich dogs have died after bitingthem.

The noise sometimes produced bylarge breeding choruses of frogs fol-lowing heavy rains can be annoying tohumans. These aggregations usuallylast only a few days, however, and sel-dom warrant control. Similarly, com-plaints sometimes arise when largenumbers of young frogs leave theponds en masse, but the frogs dispersequickly, and the “problem” will takecare of itself in a few days.

Legal Status

Laws pertaining to frogs vary fromstate to state. Some rare species (forexample, Houston toad, Wyomingtoad, Pine Barrens treefrog) may befully protected under federal or statelaws. Seasons and bag limits mayapply to other species (bullfrogs, forexample). Permits to remove frogs thatare causing damage are available insome states. Contact your state wildlifedepartment to determine the legalstatus of frogs in your area.


Exclusion

The effectiveness of exclusion dependsin part on the species involved. Mostspecies responsible for potential or realdamage can be effectively excludedfrom limited areas. Giant toads (south-

ern Florida, extreme southern Texas)or Colorado River toads (southernArizona, extreme southeastern Califor-nia) can be excluded from pet enclo-sures by placing a strip of 1/8-inch(0.3-cm) mesh hardware cloth alongthe outside base of the perimeter fence.The hardware cloth should be buriedat least 4 inches (10 cm) in the groundand should extend to a height of atleast 20 inches (50 cm). A similar exclu-sion fence can be used to controlbreeding aggregations of nonclimbingspecies in small, urban stormwaterdetention basins or to exclude thesespecies from small hatchery ponds.Although treefrogs and some relatedspecies will readily climb such a fence,most treefrogs normally breed in sea-sonal, fish-free waters. In addition,their eggs and tadpoles are readilyeaten by fish, so they do not usuallypresent a significant problem on fishfarms.


Keep the shoreline of ponds free ofemergent vegetation to minimize coverfor adult frogs and allow predators toassist in control. Efforts to directlyremove adult frogs at night will also befacilitated.

Frightening

Not applicable.

Repellents


Toxicants


Fumigants


Trapping

Place funnel traps along the base of aperimeter fence. Toads may also betrapped by burying several 5-gallon(19-l) buckets flush with the groundsurface beneath an overhead light.Toads attracted by the insects drawnto the light will fall into the bucketsand be unable to escape.

Caution: traps may capture other non-target species, including snakes,turtles, and small mammals.

Capture

Frogs can be located at night by the re-flection of their eyes in the beam of aheadlamp. They can be collected bygig or hand. Captured frogs may beeaten, or where allowed by law, soldto provide additional economicreturns. Check with your state wildlifeagency regarding seasons, bag limits,legal methods of take, and restrictionson sale.

Shooting

Although shooting is allowable insome states, it is not safe in some areasrequiring control.

Economics of Damageand Control

Frogs eat many insect pests. With theexception of fish farms, control mea-sures for frogs are seldom warrantedand, in most cases, should be discour-aged. On fish farms, the economicdamage depends in part on the unitvalue of the fish produced. Corse andMetter (1980) provided data suggest-ing that a 350-pond farm that pro-duced goldfish might sustain $42,000in annual losses to bullfrogs, whereasthe same facility might sustain only$12,600 in losses if it produced goldenshiners, a less valuable species. It fol-lows that losses might be still higheron farms specializing in valuableaquarium fishes.

Acknowledgments

Figure 1 by Randy Babb, Arizona Game andFish Department.


Altig, R. 1970. A key to the tadpoles of thecontinental United States and Canada.Herpetol. 26:180-207.

Bogert, C. M. Sounds of North American frogs:the biological significance of voice in frogs.(Record or cassette. Calls of 50 species.)Distributed by Rounder Records,Cambridge, Massachusetts, and SmithsonianFolkways Records, Rockville, Maryland.

Boyd, S. H. 1975. Inhibition of fish reproductionby Rana catesbeiana larvae. Physiol. Zool.48:225-234.

Conant, R., and J. T. Collins. 1991. A field guideto reptiles and amphibians: eastern andcentral North America. Houghton MifflinCo., Boston. 450 pp.

Corse, W. A., and D. E. Metter. 1980. Economics,adult feeding and larval growth of Ranacatesbeiana on a fish hatchery. J. Herpetol.14:231-238.

Duellman, W. E., and L. Trueb. 1986. Biology ofamphibians. McGraw-Hill Book Co., NewYork. 670 pp.

Elliot, L. 1992. The calls of frogs and toads:Eastern and Central North America.(Cassette and booklet. Calls of 42 species.)Chelsea Green Pub. Co. Post Mills, Vermont.

Johnson, T. R. Talking toad and frog poster andcassette. (Includes 20 frogs found inMissouri.) Missouri Dep. Conserv., JeffersonCity.

Kellogg, P. P., and A. A. Allen. Voices of thenight. (Calls of 34 species found in easternNorth America). Houghton Mifflin Co. (forthe Cornell Lab. Ornith.), Boston.

Stebbins, R. C. 1985. A field guide to westernreptiles and amphibians. Houghton MifflinCo., Boston. 336 pp.


F-11

SALAMANDERS

Repellents


Toxicants


Fumigants

Not applicable.

Trapping

Not applicable.

Shooting

Not applicable.


All openings 1/4 inch (0.6 cm) andlarger should be sealed to excludesalamanders.


Remove all items that lie close to theground in damp areas, such aslumber or woodpiles.

Frightening

Not applicable.

James L. ByfordProfessor and DeanSchool of Agriculture and

Home EconomicsThe University of Tennessee, MartinMartin, Tennessee 38238

Fig. 1. Tiger salamander, Ambystoma tigrinum.Considerable variation in color pattern occurs inthis species.





Identification

Salamanders are smooth-skinned am-phibians with no skin covering such asscales, hair, or feathers. They do nothave claws. Adult salamanders can bedistinguished from frogs and toads bythe presence of a tail and by the nearlyequal size of their front and hindlimbs. Most salamanders are moist orslimy to the touch, which is a goodway to distinguish them from lizards,which are dry.

The waterdog, which is completelyaquatic (water living), can be recog-nized by its featherlike external gills.

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FE DAMAGE — 1994

F-14

Range

There are several dozen kinds ofsalamanders found in the UnitedStates, but most occur only in parts ofone or several states. Becausesalamanders are so dependent onspecific habitat conditions, theirmovements are limited and homeranges are usually very small.

Habitat

Salamanders depend on water andmoisture for their existence. Becausethey do not have a skin covering, theydehydrate rapidly in dry environ-ments. The larvae spend the first partof their lives in water. After the larvalform changes to the adult form, mostsalamanders leave the water and livein moist areas on land. They canusually be found under logs, underrocks, near streams, and in other areaswhere the ground is moist and shadedfrom the sun.

Food Habits

All salamanders are predators. Theycommonly eat insects, slugs,earthworms, and other invertebrates.Some eat leeches, tiny mollusks,crustaceans, and frogs’ eggs. Asaquatic larvae, they typically eataquatic invertebrates, but some mayeven be cannibalistic.

Behavior

Salamanders generally are active whenthere is no sunshine—at night or oncloudy, rainy days. On sunny daysthey generally hide in moist areas,such as under stones and logs. Sincesalamanders are mostly nocturnal(active at night), they are seldom seenby people.

Damage

Salamanders do not cause damage topeople or property. Occasionally, theyfrighten people who are not familiarwith them. None have a poisonousbite.

Legal Status

Salamanders are protected in moststates, as are other nongame animals.In some areas, they may be legallytaken to use as bait for fishing, but inmost areas they are completely pro-tected. Some salamanders are on statelists of threatened and endangeredspecies.


Salamanders generally do not enterbuildings. On occasion, they may befound in a damp basement, if the base-ment stays moist most of the time andthere are items lying close to the dampfloor. In such cases, all openings 1/4inch (0.6 cm) and larger should besealed to exclude salamanders. Checkfor openings around the corners ofdoors and windows, water pipes, andelectric service entrances. Holes inmasonry foundations (poured concreteand concrete blocks or bricks) shouldbe sealed with mortar. Openings inwood should be sealed with fine mesh(1/8-inch [0.3-cm]) hardware clothand/or sheet metal.


In situations where salamanders areinside buildings, steps should be takento dry out the basement area (see aconstruction specialist for this) orremove objects from the floor of dampbasements where salamanders canhide. Keep areas outside of buildingsfree from objects that salamanders canhide under—lumber, sticks, oldboards, or firewood. If such items areoff the ground (stacked on runners)the soil underneath can dry, makingthe area unattractive to salamanders.

Frightening

Not applicable.

Repellents


Toxicants


Fumigants

Not applicable.

Trapping

Not applicable.

Shooting

Not applicable.


As mentioned earlier, salamanders arecompletely harmless. They do nothave a poisonous bite and cause nohazard to people, except perhapsfrightening them. They cause no dam-age to personal property. Therefore,expense toward control of salaman-ders is not justified. Most methodsrequired to remove salamanders areinexpensive and are consistent withgood grooming of the yard and homeenvironment.

Acknowledgments

Figure 1 by Emily Oseas Routman.


Barker, W. 1964. Familiar reptiles andamphibians of America. Harper & Row.New York. 220 pp.

Cochran, D. M. 1961. Living amphibians of theworld. Doubleday. New York. 199 pp.

Conant, R. 1975. A field guide to reptiles andamphibians of eastern and central NorthAmerica, 2d ed. Houghton Mifflin Co.,Boston. 429 pp.

Goin, C. J., and O. B. Goin. 1962. Introduction toherpetology. W. H. Freeman, San Francisco.341 pp.

Huheey, J. E., and A. Stupka. 1967. Amphibiansand reptiles of the Great Smoky MountainsNational Park. Univ. Tennessee Press.Knoxville. 98 pp.

Schlauch, F. C. 1976. City snakes, suburbansalamanders. Nat. Hist. 85:46-53.


F-15

NONPOISONOUSSNAKES

Frightening

Not applicable.

Repellents

Several snake repellents have beenpromoted, but none are consistentlyeffective.

Toxicants


Fumigants


Trapping

A funnel trap with drift fences can beused.

Shooting

Nonpoisonous snakes are protected bylaw in most states and indiscriminatekilling is illegal. Shooting or clubbingis effective, however, where it isallowed, with permission from thestate wildlife agency.

James L. ByfordProfessor and DeanSchool of Agriculture and

Home EconomicsThe University of Tennessee, MartinMartin, Tennessee 38238


Seal all openings (1/4 inch [0.6 cm]and larger) with mortar, 1/8-inch(0.3-cm) hardware cloth, sheetmetal, or steel wool.

A snake-proof fence can be used toexclude snakes.


Reduce rodent populations.

Keep all vegetation closely mowed;remove bushes, shrubs, rocks,boards, firewood, and debris lyingclose to the ground, especiallyaround buildings.

Alter all sites that provide cool, damp,dark habitat for snakes.

Fig. 1. Bullsnake (gopher snake), Pituophismelanoleucus

Other Methods

Remove snakes from inside buildingsby placing piles of damp burlapbags or towels in areas wheresnakes have been seen. After snakeshave been attracted, remove thebags and snake(s) from thebuilding.

Glue boards can be used to capturesnakes found inside houses or otherbuildings. Once caught, the snakeand board can be taken outside. Thesnake can be released unharmed bypouring vegetable oil on it (the oilcounteracts the adhesive).

Since nonpoisonous snakes arecompletely harmless, controlprograms for them are not necessary.Learn how to distinguish betweenpoisonous and nonpoisonous snakesin your area.

PREVENTION AND CONTROL OF WILDLIFE DAMAGE — 1994




F-16

Nonpoisonous

Poisonous

Fig. 2. Nonpoisonous snakes have two rows of scales between the vent and the tip of the tail, whilepoisonous snakes have only one row.

Round pupil

Nostril

Fig. 3. Nonpoisonous snakes have a round eye pupil and have no pit between the eye and the nostril.

Identification

Of the many kinds of snakes found inthe United States, only the followingare harmful: rattlesnakes, copper-heads, cottonmouths, coral snakes,and sea snakes. The latter group livesonly in the oceans. All poisonoussnakes, except coral snakes and seasnakes, belong in a group called pitvipers. There are three ways to distin-guish between pit vipers andnonpoisonous snakes in the UnitedStates:

(1) All pit vipers have a deep pit oneach side of the head, midwaybetween the eye and the nostril.Nonpoisonous snakes do not havethese pits.

(2) On the underside of the tail ofpit vipers, scales go all the wayacross in one row (except on thevery tip of the tail, which may havetwo rows in some cases). On theunderside of the tail of all non-poisonous snakes, scales are in tworows all the way from the vent ofthe snake to the tip of the tail (Fig.2). The shed skin of a snake showsthe same characteristics.

(3) The pupil of pit vipers is verti-cally elliptical (egg-shaped). In verybright light, the pupil may bealmost a vertical line, due toextreme contraction to shut outlight. The pupil of nonpoisonoussnakes is perfectly round (Fig. 3).

The poisonous coral snake is ringedwith red, yellow, and black, with redand yellow rings touching. Non-poisonous mimics of the coral snake(such as the scarlet king snake) havered and yellow rings, separated byblack rings. A helpful saying to memo-rize is: “Red on yellow, kill a fellow;red on black, friend of Jack.”

Range

Some species of nonpoisonous snakesoccur throughout several states, butthe majority have only limited ranges.

Habitat

Snakes are not very mobile, and eventhough some are fairly adaptable, mosthave specific habitat requirements.Some live underground (these aremostly small in size), and some haveeyes shielded by scales of the head.Others, such as green snakes, live pri-marily in trees. One group spends itsentire life in the oceans. In general,snakes like cool, damp, dark areaswhere they can find food. The follow-ing are areas around the home thatseem to be attractive to snakes: fire-wood stacked directly on the ground;old lumber piles; junk piles; flowerbeds with heavy mulch; gardens;unkempt basements; shrubbery grow-ing against foundations; barn lofts—especially where stored feed attractsrodents; attics in houses where there isa rodent or bat problem; stream banks;pond banks where there are boards,innertubes, tires, planks, and otheritems lying on the bank; unmowedlawns; and abandoned lots and fields.

Food Habits

All snakes are predators, and the dif-ferent species eat many different kindsof food. Rat snakes eat primarilyrodents (such as rats, mice, and chip-munks), bird eggs, and baby birds.King snakes eat other snakes, as wellas rodents, young birds, and bird eggs.Some snakes, such as green snakes, eatprimarily insects. Some small snakes,such as earth snakes and worm snakes,eat earthworms, slugs, and salaman-ders. Water snakes eat primarily frogs,fish, and tadpoles.


Snakes are specialized animals, havingelongated bodies and no legs. Theyhave no ears, externally or internally,and no eyelids, except for a protectivewindow beneath which the eye moves.The organs of the body are elongated.Snakes have a long, forked tongue,

Fig. 4. Though fairly expensive, a properly constructed snake-proof fence can keep snakes from en-tering a given area.

which helps them smell. Gaseous par-ticles from odors are picked up by thetongue and inserted into the two-holedorgan, called the Jacobson’s Organ, atthe roof of the mouth.

The two halves of the lower jaw arenot fused, but are connected by a liga-ment to each other. They are alsoloosely connected so the snake canswallow food much larger than itshead. Because snakes are cold-bloodedand not very active, one meal may lastthem several weeks. Also, becausethey are cold-blooded, they may hiber-nate during cold weather months oraestivate during hot summer monthswhen the climate is severe. In eithercase, they consume little or no foodduring these times. Some snakes layeggs, some hatch their eggs inside thebody, and some give live birth. Theyoung of copperheads, rattlesnakes,and cottonmouths are born alive.

Nonpoisonous snakes are harmless tohumans. In most cases, a snake willcrawl away when approached if it feelsit can reach cover safely. No snakescharge or attack people, with theexception of the racers, which occa-sionally bluff by advancing toward anintruder. Racers will retreat rapidly,however, if challenged. Snakes reactonly when cornered. Different speciesreact in different ways, playing deadby turning over on the back, hissing,opening the mouth in a menacingmanner, coiling, and striking andbiting if necessary.


A nonpoisonous snake bite has novenom and can do no more harm thanfrighten the victim. After being bittenseveral thousand times by non-poisonous snakes, the author and hisstudents have never suffered anyadverse reaction, and no treatmentwas ever used. The only harm non-poisonous snakes can cause is frighten-ing people who are not familiar withthem. A bite from a poisonous snake,however, causes an almost immediatereaction—swelling, tissue turning adark blue-black, a tingling sensation,and nausea. If none of these is

observed or felt, the bite was from anonpoisonous snake. Also, bites fromone of the pit vipers (copperheads,rattlesnakes, and cottonmouths) willreveal two fang marks, in addition toteeth marks. All snakes have teeth;only pit vipers have fangs. NorthAmerican pit vipers have only tworows of teeth on top and two on thebottom, whereas nonpoisonous snakeshave four on top and four on thebottom.

Legal Status

In most states, snakes are considerednongame wildlife and are protected bystate law unless they are about tocause personal or property damage.Therefore, snakes should not be indis-criminately killed. Some species arelisted on federal and/or state threat-ened and endangered species lists.


Snakes enter houses, barns and otherbuildings when habitat conditions aresuitable inside the buildings. They areparticularly attracted to rodents andinsects as well as cool, damp, darkareas often associated with buildings.All openings 1/4 inch (0.6 cm) andlarger should be sealed to excludesnakes. Check the corners of doors andwindows, as well as around waterpipe and electrical service entrances.Holes in masonry foundations (poured

concrete and concrete blocks or bricks)should be sealed with mortar toexclude snakes. Holes in woodenbuildings can be sealed with fine mesh(1/8-inch [0.3-cm]) hardware cloth orsheet metal.

In some cases, the homeowner may getpeace of mind by constructing a snake-proof fence around the home or yard(Fig. 4). A properly constructed snake-proof fence will keep out all poisonoussnakes and most harmless snakes(some nonpoisonous snakes are fairlygood climbers). The cost of fencing awhole yard may be high, but it costslittle to enclose a play space for chil-dren too young to recognize danger-ous snakes. The following design istaken from information from the USFish and Wildlife Service.

The fence should be made of heavygalvanized hardware cloth, 36 inches(91 cm) wide with a 1/4-inch (0.6-cm)mesh. The lower edge should be bur-ied 6 inches (15 cm) in the ground, andthe fence should be slanted outwardfrom the bottom to the top at a 30o

angle (Fig. 5). Place supporting stakesinside the fence and make sure thatany gate is tightly fitted. Gates shouldswing inward because of the outwardslope of the fence. A 36-inch (91-cm)vertical fence with a 12-inch (30-cm) lipat the top, facing outside and angleddownward at a 30o angle would prob-ably work as well. Any opening underthe fence should be firmly filled—con-crete is preferable. Mow all vegetationjust outside the fence, for snakes might

F-17

F-18

Fig. 5. Side view of a drift fence to excludesnakes.

Fig. 6. A funnel trap with a drift fence is one way to catch snakes.

30o

(Stakes inside)

Fence

4 to 6"Underground

Drift fence

FunnelFunnel

Drift fence

use these plants to help climb over thefence. If children tend to crush thefence, it must be supported by moreand sturdier stakes and by strong wireconnected to its upper edge.


The primary food of most snakes,especially the larger ones, is birds, birdeggs, and rodents such as rats, mice,and chipmunks. No control programfor rodent-eating snakes is ever com-plete without removing rodents androdent habitats. Put all possiblesources of rodent food in secure con-tainers. Be sure to keep all dog or catfood cleaned up after each feeding andmake the stored food unavailable tothe rodents. Keep all vegetation closelymowed around buildings. Removebushes, shrubs, rocks, boards, and de-bris of any kind lying close to theground, as these provide cover forboth rodents and snakes. Refer to thechapters on rodents for more informa-tion on their control.

Frightening

Not applicable.

Repellents

Several repellents have been used inthe past, but none has been consis-tently effective. Currently Dr. T’sTM

Snake-A-Way® is registered for thecontrol of rattlesnakes and the check-ered garter snake, but is apparentlynot effective against most species ofsnakes. Active ingredients include sul-fur and naphthalene. Band applica-tions around the area to be protectedare recommended.

Toxicants


Fumigants

There are no legal fumigants to killsnakes. Moreover, because mostsnakes do not burrow, using fumi-gants in underground burrows is not afeasible method of control. In the past,pest control operators have completelyencased houses with plastic and fumi-gated at tremendous expense to thehomeowner (several thousand dol-lars). This is not a reasonable controlmethod for nonpoisonous snakes sincethe animals being killed are completelyharmless.

Trapping

One method reported by researchersto catch snakes involves a funnel trapwith drift fences constructed of 1/4-inch or 1/2-inch (0.6- or 1.3-cm) meshhardware cloth erected 2 feet (0.6 m)high and 25 feet (7.5 m) long. Posts fordrift fences should be on the back sideof the fence. These fences guide ani-mals into the funnel end of the trap(Fig. 6).

One type of funnel trap can be madeby rolling a 3 x 4-foot (0.9 x 1.2-m)piece of 1/4-inch (0.6-cm) mesh hard-ware cloth into a cylinder about 1 foot(0.3 m) in diameter and 4 feet (1.2 m)long. An entrance funnel can be madesimilarly and fitted into one end of thecylinder. Close the other end of the

cylinder with hardware cloth andattach the drift fence. To catch the ani-mal from either direction, put anotherfunnel at the other end of the trap andanother drift fence facing the oppositedirection.

Shooting

Nonpoisonous snakes are protected bylaw in most states, and indiscriminatekilling is illegal. Shooting or clubbing isextremely effective in states where it isallowed and will soon eliminate thesnake population. Permission may berequired from the local state wildlifeagency.

Other Methods

It is not difficult to remove snakesfrom inside a house or other buildings.Place piles of damp burlap bags ortowels in areas where snakes havebeen seen or are likely to be found.Cover each pile with a dry burlap bagor towel to slow evaporation. Snakesare attracted to damp, cool, dark areassuch as these piles. After the bags ortowels have been out for a couple ofweeks, completely remove them witha large scoop shovel during the middleof the day when snakes are likely to beinside or underneath.

Glue boards have proven to be usefulfor trapping snakes in or under build-ings. Securely tack several rodent gluetraps (or use bulk glue) to a plywoodboard approximately 24 x 16 inches

(61 x 41 cm) to make a glue patch atleast 7 x 12 inches (15 to 30 cm). Placethe board against a wall where snakesare likely to travel. Snakes becomestuck when they try to cross the board.Do not place the board near any object(pipes or beams) that the snake can usefor leverage in attempting to free itself.A hole drilled through the plywoodboard will allow removal of the boardand the entrapped snake with a longstick or hooked pole. Animals trappedin the glue can be removed with theaid of vegetable oil, which counteractsthe adhesive.

Do not use glue boards outdoors or inany location where they are likely tocatch pets or nontarget wildlife. Theglue can be quite messy and is hard toremove from animals.


As mentioned earlier, nonpoisonoussnakes are completely harmless andcause no damage, except occasionallyfrightening people. Therefore, noexpense toward control of non-poisonous snakes is justified. Mostmethods to remove snakes are inex-pensive, except for the snake-prooffence, which can be quite expensive.

AcknowledgmentsAppreciation is expressed to the US Fish andWildlife Service for some of the informationpresented in this chapter, particularly the designof the snake-proof fence.

Figures 1 through 3 by Emily Oseas Routman.

Figures 4 through 6 by Jill Sack Johnson.

For AdditionalInformationBoys, F. E. 1959. Poisonous amphibians and

reptiles. C. C. Thomas Co., Springfield,Illinois. 149 pp.

Conant, R. 1975. A field guide to reptiles andamphibians of eastern and central NorthAmerica. Houghton Mifflin Co., Boston.429 pp.

Ditmars, R. L. 1939. A field book of NorthAmerican snakes. Doubleday, Doran, andCo., New York. 305 pp.

Ditmars, R. L. 1966. Snakes of the world.Macmillan Co., New York, 207 pp.

Huheey, J. E., and A. Stupka. 1967. Amphibiansand reptiles of the Great Smokey MountainsNational Park. Univ. Tennessee Press,Knoxville. 98 pp.

Lamburn, J. B. C. 1964. Snake lore. Doubledayand Co., New York. 152 pp.

Leviton, A. E. 1971. Reptiles and amphibians ofNorth America. Doubleday and Co., NewYork. 250 pp.

Parker, H. W. 1977. Snakes — a natural history.Cornell Univ. Press, 124 pp.

Schlauch, F. C. 1976. City snakes, suburbansalamanders. Nat. Hist. 85:46-53.

Schmidt, K. P., and D. D. David. 1941. Fieldbook of snakes of the United States andCanada. G. P. Putnam’s Sons. New York.365 pp.

Simon, H. 1973. Snakes: the facts and thefolklore. Viking Press, New York. 128 pp.

Stidworthy, J. 1972. Snakes of the world. BantamBooks, Inc., 159 pp.


F-19

RATTLESNAKESWalter E. HowardProfessor Emeritus of Wildlife Biology

and Vertebrate EcologyDepartment of Wildlife, Fisheries

and Conservation BiologyUniversity of CaliforniaDavis, California 95616

Fig. 1. Prairie rattlesnake, Crotalus viridis viridis





Damage Prevention andControl Methods*Exclusion

Construct a snake-proof fence aroundareas of human activity.

Seal entrances to buildings andstructures.


Eliminate shelter for snakes.

Control rodents; they attract snakes.

Repellents

None are available.

Toxicants

None are available.

Fumigants

Generally not effective in dens.

Trapping

Effective in some situations whenproperly placed.

Glue boards are useful in removingrattlesnakes from buildings.

Shooting

Effective where safe.

Other Methods

Organized snake hunts may besuccessful in spring or earlysummer.

Snake Bite

Wear protective clothing and becareful when climbing and walking.

If a bite occurs, keep the victim calm,warm, and reassured. Seek medicalattention immediately.

*Information pertains to other poisonous snakes.

Introduction

Rattlesnakes are distinctly Americanserpents. They all have a jointed rattleat the tip of the tail, except for one rarespecies on an island off the Mexicancoast. This chapter concerns the genusCrotalus, of the pit viper familyCrotalidae, suborder Serpentes. Sincesnakes evolved from lizards, bothgroups make up the order Squamata.

This article describes the characteris-tics of the common species of rattle-snakes that belong to the genusCrotalus. These include the easterndiamondback, (C. adamanteus); thewestern diamond (back) rattlesnake,(C. atrox); the red diamond rattlesnake,(C. ruber); the Mohave rattlesnake,(C. scutulatus); the sidewinder, (C.ceraster); timber rattlesnake, (C.horridus); three subspecies of the west-ern rattlesnake, (C. viridis): the prairierattlesnake (C. v. viridis); the GreatBasin rattlesnake (C. v. lutosus); andthe Pacific rattlesnake (C. v. oreganus).

F-21

FE DAMAGE — 1994

F-22

Elliptical eye pupil

Nostril

Fig. 2. Rattlesnake head showing “cat-eye” elliptical pupil and location of the large loreal pit, charac-teristic of pit vipers.

Loreal pit opens forward

There are 15 species of rattlesnakes inthe United States and 25 in Mexico.Other front-fanged poisonous snakesof the Crotalidae family, which are notincluded in this discussion, are themassasauga and pigmy rattlesnakes,both of the genus Sistrurus. Also notincluded are two snakes that do nothave rattles, hence are not called rattle-snakes: the water moccasin or cotton-mouth, and the copperhead, both ofthe genus Agkistrodon. Two other gen-era of poisonous snakes in NorthAmerica are coral snakes (Micrurusand Micruroides) of the familyElapidae.

Identification

Rattlesnakes are usually identifiedby their warning rattle — a hiss orbuzz — made by the rattles at the tipof their tails. A rattlesnake is born witha button, or rattler, and acquires a newrattle section each time it molts. Rattle-snakes also are distinguished by hav-ing rather flattened, triangular heads.The heads of all Crotalus rattlesnakesare about twice as wide as their necks.Only pit vipers possess this head con-figuration; coral snakes do not.

Rattlesnakes belong to the pit viperfamily Crotalidae, so named becauseall possess visible loreal pits, or lateralheat sensory organs, between eye andnostril on each side of the head (Fig. 2).These heat sensory pits are not presentin true vipers, which do not occur inthe Western Hemisphere. The facialpits enable rattlesnakes to seek out andstrike, even in darkness, warm objectssuch as small animal prey, as well aslarger animals that could be a threat.The vertically elliptical eye pupils, or“cat eyes,” are also a characteristic ofrattlesnakes (Fig. 2). Identifying a deadrattler whose rattles are missing can bedone by looking at the snake’s scaleson the underside in the short regionbetween the vent and the tip of the tail.If the scales are divided down the cen-ter, the snake is harmless. The scaleson rattlesnakes are not divided.

Rattlesnakes come in a great variety ofcolors, depending on the species andstage of molt. Most rattlers are variousshades of brown, tan, yellow, gray,

black, chalky white, dull red, and olivegreen. Many have diamond, chevron,or blotched markings on their backsand sides.

Range and Habitat

Rattlesnakes occur only in North andSouth America and range from sealevel to perhaps 11,000 feet (over 3,000m) in California and 14,000 feet (4,000m) in Mexico, although they are notabundant at the higher elevations.They are found throughout the GreatPlains region and most of the UnitedStates, from deserts to dense forestsand from sea level to fairly high moun-tains. They need good cover so theycan retreat from the sun. Rattlers arecommon in rough terrain and wher-ever rodents are abundant.

Food Habits

Young or small species of rodentscomprise the bulk of the food supplyfor most rattlesnakes. Larger rattlersmay capture and consume squirrels,prairie dogs, wood rats, cottontails,and young jackrabbits. Occasionally,even small carnivores like weasels andskunks are taken. Ground-nestingbirds and bird eggs can also make upan appreciable amount of the diet ofsome rattlers. Lizards are frequentlytaken by rattlers, especially in theSouthwest. The smaller species ofrattlesnakes and young rattlesnakesregularly feed on lizards and amphib-ians.

Rattlesnakes consume about 40% oftheir own body weight each year.Many prey are killed but not eaten byrattlesnakes because they are too large

or cannot be tracked after being struck.One male rattler captured in the fieldhad consumed 123% of its weight, butyoung rattlers frequently die due tolack of food. Domestically raised rat-tlesnakes will survive when fed onlyonce a year, but in the field, snakesusually feed more than once, depend-ing on the size of prey consumed. Asnake may kill several prey, one afteranother, and of different species.When rodents and rabbits are struck,the prey is immediately released. Thesnake then uses its tongue to track theprey to where it has died.

Digestion is quite slow and usually nobones remain in the feces, called“scats.” Hair, feathers, and sometimesteeth, however, can usually be identi-fied in scats. Rattlesnakes use verylittle energy except when active, andthey probably are active for less than10% of their lives. They are not veryactive unless food is scarce. They storemuch fat in their bodies, which can lastthem for long periods.


When a rattlesnake strikes its prey orenemy, the paired fangs unfold fromthe roof of its mouth. Prior to thecompletion of the forward strikemotion, the fangs become fully erect atthe outer tip of the upper jaw. Theerectile fangs are hollow and work likehypodermic needles to inject amodified saliva, the venom, into theprey. Rattlesnakes can regulate theamount of venom they inject whenthey strike.

Replacement fangsin sheath

Opening to hollowfang is a groove onouter surface

Teeth

Right venomgland

Fig. 3. Head of a rattlesnake in striking position. Supple-mentary fangs are covered by a sheath of tissue. Eachfang is located in a double socket. Replacement fangsappear in what are currently empty sockets.

Mature fangs generally are shed sev-eral times a season. They may becomeembedded in the prey and may evenbe swallowed with the prey. When onemature fang in a pair is lost, it willsoon be replaced by another functionalmature fang. A series of developingfangs are located directly behind oneanother in the same sheath at the roofand outer tip of the mouth (Fig. 3). If anewly replaced fang is artificiallyremoved, it may require weeks orlonger before another replacement willbe fully effective. One fang can func-tion, however, while the other in thepair is being replaced. Fangs that getstuck in a person’s boot are not verydangerous; they cannot contain muchvenom since they serve only as a hol-low needle. The external opening ofthe hollow fang is a groove on the out-side of the fang, set slightly back fromthe tip to prevent it from becomingplugged by tissue from the prey(Fig. 3).

Rattlesnakes cannot spit venom, butthe impact of a strike against an objectcan squeeze the venom gland, locatedin the roof of the mouth, and venommay be squirted. This can happenwhen a rattler strikes the end of a stickpointed at it, or the wire mesh of asnake trap. The venom is releasedinvoluntarily if sufficient pressure isexerted, as occurs when venom is arti-ficially “milked” from live snakes.Such venom is dangerous only if itgets into an open wound. Alwayswear protective clothing when han-dling rattlesnakes.

Female rattlesnakes are ovoviviparous.That is, they produce eggs that are re-tained, grow, and hatch internally. Theyoung of most species of rattlesnakesare 6 to 8 inches (15 to 20 cm) whenborn. They are born with a single rattleor button, fangs, and venom. They canstrike within minutes, but being sosmall, they are not very dangerous.Average broods consist of 5 to 12young, but sometimes twice as manymay be produced.

The breeding season lasts about 2months in the spring when the snakesemerge from hibernation. Sperm isthought to survive in the female as

long as a year. During summer, preg-nant females usually do not feed, sofew are ever captured that containeggs about to hatch. The young areborn in the fall. Most rattlesnakes aremature in 3 years, but may requiremore time in northerly areas. Rattle-snakes may not produce young everyyear.

The sex of a rattlesnake is not easy todetermine. Even though the tail of therattlesnake (the distance between thevent and the rattles) is quite short, it ismuch longer in males than in femalesof the same size. The pairedhemipenises of male snakes are notvisible except during mating, whenone of these paired hollow organs isturned inside out and extruded fromthe cloaca. If both are extruded artifi-cially, they appear like two forked,stumpy legs.

Snakes never close their eyes, sincethey have no eyelids. They are deaf,but can detect vibrations. They have agood sense of smell and vision, andtheir forked tongues transport micro-

scopic particles from the environmentto sensory cells in pits at the roof of themouth. A rattlesnake uses these pits totrack prey it has struck and to gatherinformation about its environment.

Snakes have a large number of ribsand vertebrae with ball-and-socketjoints. Each rib is joined to one of thescales on the snake’s underside. Thesnake accomplishes its smooth flowingglide by hooking the ground with itsscales, which are then given a back-ward push from the ribs. Rattlesnakesoften look much larger when seen livethan after they have been killed. Thishappens because their right lungextends almost the full length of thetubular body, and when the snakesinhale they can appear much fatter andmore threatening. The expulsion of theair can produce a hiss.

Rattlesnakes, like other snakes, peri-odically shed their skin. When the newskin underneath is formed, the snakerubs its snout against a stone, twig, orrough surface until a hole is wornthrough. After it works its head free,

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the snake contracts its muscles rhyth-mically, pushing, pulling, and rubbing,until it can crawl out of the old skin,which peels off like an inverted stock-ing. Each molt produces a new rattle.Some rattles usually break off fromolder snakes. Even if no rattles havebeen lost, they do not indicate exactage because several rattles may be pro-duced in one season.

Even though the optimum tempera-ture for rattlesnakes is around 77o to89o F (25o to 32o C), the greatest periodof activity is spring, when they comeout of hibernation and are seekingfood. If lizards are active, be alert forrattlesnakes. The activity period forrattlers can vary from about 10 monthsor so in warm southern regions to per-haps less than 5 months in the northand at high elevations. Dependingupon availability of good, dry denningsites below the frost line, rattlesnakesmay hibernate alone or in small num-bers. However, sometimes they den inlarge groups of several hundred inabandoned prairie dog burrows orrock caverns, where they lie torpid ingroups or “balls.” All dens must bedeep enough so the temperature is notaffected by occasional warm days. Ifnot, the snakes might emerge too earlyin spring only to become sluggish andvulnerable should the weather againturn cold. Since snakes are cold-blooded animals and their body tem-perature is altered by air temperature,refrigeration makes them sluggish andeasy to handle for displaying.

Rattlesnakes usually see humans be-fore humans see them, or they detectsoil vibrations made by walking. Theycoil for protection, but they can strikeonly from a third to a half of theirbody length. Rattlers rely on surpriseto strike prey. Once a prey has beenstruck, but not killed, it is unlikely thatit will be struck again. Experiencedrodents and dogs can evade rattle-snake strikes.

Rattlesnakes may appear quite aggres-sive if exposed to warm sunshine.Since they have no effective coolingmechanism, they may die from heatstroke if kept in the sun on a hot daymuch longer than 15 or 20 minutes.

If a rattlesnake has just been killed bycutting off its head, it can still bare itsfangs and bite. The heat sensory pitswill still be functioning, and thewarmth of a hand will activate thestriking reflex. The head cannot strike,but it can bite and inflict venom. Thereflex no longer exists after a few min-utes, or as long as an hour or more if itis cool, as rigor mortis sets in.


The greatest danger to humans fromrattlesnakes is that small children maybe struck while rolling and tumbling inthe grass. Only about 1,000 people arebitten and less than a dozen people diefrom rattlesnake venom each year inthe United States. Nevertheless, it is amost unpleasant experience to bestruck. The venom, a toxic enzymesynthesized in the snake’s venomglands, causes tissue damage, as ittends to quickly tenderize its prey.When known to be abundant, rattle-snakes detract from the enjoyment ofoutdoor activities. The human fear ofrattlesnakes is much greater than thehazard, however, and many harmlesssnakes inadvertently get killed as a re-sult. Death from a rattlesnake bite israre and the chance of being bitten inthe field is extremely small.

Experienced livestock operators andfarmers usually can identify rattle-snake bites on people or on livestockwithout much difficulty, even if theydid not witness the strike. A rattle-snake bite results in almost immediateswelling, darkening of tissue to a darkblue-black color, a tingling sensation,and nausea. Bites will also reveal twofang marks in addition to other teethmarks (all snakes have teeth; only pitvipers have fangs too). Rattlesnakes of-ten bite livestock on the nose or headas the animals attempt to investigatethem. Sheep, in particular, may crowdtogether in shaded areas near waterduring midday. As a consequence,they also frequently are bitten on thelegs or lower body when pushed closeto snakes. Fang marks and tissue dis-coloration that follows in the majorblood vessels from the bite area are

usually apparent on livestock that arebitten (see Wade and Bowns 1982,pages 32 and 34 in the Damage Identi-fication section of this book).

Legal Status

Most species of rattlesnakes are not con-sidered threatened or endangered. Sincethey are potentially dangerous, there hasnot been much support for protectingthem except in national parks and pre-serves. However, since there are stateand local restrictions, contact local wild-life agencies for more information.


An occasional single poisonous snakecan be destroyed if one has enoughdetermination. In areas where thehabitat is favorable for rattlesnakes,copperheads, or water moccasins, asignificant reduction in their popula-tion density may be difficult. In snakecountry, most people learn to “keeptheir eyes open” and be cautious.

Exclusion

When feasible, the most effective wayfor a homeowner to protect a child’splay area from rattlesnakes is to con-struct a rattlesnake-proof fence aroundit. The fencing must be tight. If wiremesh is used, it should be 1/4-inch(0.6-cm) mesh and about 3 feet (1 m)high. Bury the bottom 3 or 4 inches (8or 10 cm) or bend outward 3 or moreinches of the base of the wire to dis-courage other animals from diggingunder the fence. Put the stakes on theinside and install a gate that is tight-fitting at the sides and bottom,equipped with a self-closing spring.The benefit of the fence will be lost ifwood, junk, or thick vegetationaccumulates against the outside of thefence. Vegetation that has ground-levelfoliage also provides attractive hidingplaces for rattlesnakes, so it should beremoved or properly pruned. Tight-fitting doors will prevent snakes fromentering outbuildings. The foundationsof all buildings should be sealed ortightly screened with 1/4-inch (0.6-cm)wire mesh to keep out snakes.

Drift fence

Funnel

Drift Fence

Funnel

Fig. 4. A fish-type funnel trap of 1/4-inch hardware cloth attached to an inward-sloping drift fenceof the same wire mesh can be useful in trapping snakes as they emerge from a multi-opening den.Escape will be reduced if a wooden nest box is attached to the funnel trap.


It is always desirable to use nonlethalbiological means of control whenfeasible. Although good quantified dataare not available to evaluate the effec-tiveness of removing the prey of snakes,effective, sustained rodent control willreduce the attractiveness of a rural resi-dence or other facility to rattlesnakes.Snakes will not remain in habitat madeless favorable for them. Hiding placesunder buildings, piles of debris, or densevegetation should be removed. Haybarns and feed storage areas that encour-age rodents will attract rattlers.

Frightening

No methods are known that willfrighten rattlesnakes. Sounds certainlywill not work because snakes are deaf.

Repellents

Many potential snake repellents havebeen researched, only to be found inef-fective. All species of snakes are likelyto cross a strip of repellent substance ifthey want to get to the other side.

Dr. T’sTM Snake-A-Way®, a mixture ofsulphur-naphthalene, has been registeredby EPA; however, its registration in Cali-fornia was denied as of July 1991,because required data was not submit-ted. A Y-shaped laboratory enclosurethat provided rattlers with a choice ofcrawling into a tunnel with odor or onefree of odor showed they usually chosethe passage free of odor. No field testdata is available. To be of practical use,the odor of a snake repellent must not betoo objectionable to people.

Toxicants

No effective toxicant is registered forthe control of rattlesnakes. Whenrodents were poisoned with variousrodenticides and then fed to rattle-snakes, the snakes were not affected.Apparently, digestion is too slow forthe toxicants to have an effect onsnakes.

Fumigants

It may be possible to kill rattlesnakesin burrows and rock dens with toxicgas, although this is not a very practi-cal method. Calcium cyanide is achemical frequently recommended,

but no lethal gas has had good successbecause snakes have such a slow rateof metabolism, especially when in hi-bernation. In addition, susceptible non-target species in the burrows or densmay become victims.

In the spring and early summer, whenhibernating snakes are about toemerge, gasoline poured down a bur-row or into a den will drive the snakesout. As the snakes exit they can beclubbed, shot, or captured alive withsnake tongs that secure a snake at itsneck. If transported in a bag, tie the topsecurely. Many snake hunters push ahose down a burrow and after listen-ing to confirm that rattlesnakes arepresent, pour 1 to 2 ounces (30 to 60ml) of gasoline into a funnel on thehose and then blow on the hose. Thistechnique seems quite effective for sea-sonally reducing rattlesnake numbers,but it may be lethal to nontarget ani-mals including nonpoisonous andbeneficial snakes. To be effective, com-munity-wide campaigns shouldextend over several days, since manysnakes may escape into holes orcrevices. Snake hunters should wearprotective clothing such as pants,heavy gloves, and boots.

Trapping

Various combinations of fencing andtraps at known rattlesnake dens can bevery successful if one is trying to col-lect rattlesnakes, because in some

localities several hundred rattlesnakesmay occupy the same den. If all butone opening can be blocked, it is thenquite simple to pipe or otherwise chan-nel the emerging rattlesnakes into alarge oil drum or other receptacle. If itis not possible to find all den openings,inward-sloping drift fences of 1/4-inch(0.6-cm) hardware cloth mesh, 1 or 2feet (0.5 m) high, with fish-type funneltraps (Fig. 4) will suffice. The inwardsloping funnel makes it difficult for thesnakes to escape. If a wooden nestboxis attached to one side of these traps,the snakes will usually hide in the boxand not spend as much time trying toescape. Drift-fence funnel traps alsocatch many other animals. Therefore,this control method requires dailyinspection and usually is not verypractical except at dens.

Glue boards are useful for trappingrattlesnakes that are in or under build-ings (Knight 1986). To trap rattle-snakes, use a plywood boardapproximately 24 x 16 inches (61 x 41cm). Securely tack a 6 x 12-inch (15 x30-cm) rodent glue trap (or use bulkglue to make a similar-sized gluepatch) to the plywood (Fig. 5). Placethe board against a wall, as this iswhere snakes are likely to travel. Therattlesnake will become stuck whileattempting to cross the board. Do notplace the board near any objects(pipes, beams) that the snake can usefor leverage in attempting to free itself.

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Fig. 5. A glue trap to catch rattlesnakes can bemade by attaching three to six rodent glue trapsto a wooden board.

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16

The glue trap can be removed easilyusing a long stick or pole with a hookor by an attached rope if a hole isdrilled through the plywood board.Animals trapped in the glue can beremoved with the aid of vegetable oil,which counteracts the adhesive.

Do not use glue boards outdoors or inany location where they are likely tocatch pets or desirable nontarget wild-life. The glue can be quite messy and isdifficult to remove from animals.

Shooting

A shotgun has often been used to elimi-nate individual rattlesnakes around arural homestead. Similarly, a pistolloaded with birdshot is very effective atclose range. Shooting is not consideredeffective for reducing large populations.

Other Methods

Dynamite blasting of known dens isdangerous and has questionableadvantages. There is no way to knowwhat kinds and how many snakeshave been killed, and the blast maycreate an even better den for futurerattlesnakes.

Rattlesnakes have natural predators,but the predators are not likely to helpmuch in controlling rattlesnake popu-lations. Some dogs, especially if theyhave experienced a snake bite, becomeexcellent guards for children. They willbark when a snake is discovered, andmany can kill rattlesnakes as well.Domestic geese and turkeys may alsohelp, by acting as an alarm and byfrightening snakes. Hogs do not pro-vide practical protection around ahomestead.

Snake Bite

The best protection for humans whentraveling in snake country is commonsense in choosing protective foot and

leg wear. When climbing, one shouldbeware of putting a hand up overrocks. Rattlesnakes might be waitingthere for a rodent, and the warmth in ahand may cause the snake to strikereflexively. Care should be taken atnight, when snakes are more active,and the chance of stepping on a snakeis greater. Fortunately, rattlesnakes tryto avoid people.

The best first aid for a poisonous snakebite is to seek immediate medical careand to keep the victim calm, warm,and reassured. Do not drink alcohol oruse ice, cold packs, or freon spray totreat the snake bite or cut the wound,as was once recommended.

If a victim of snake bite is several hoursfrom a car and medical aid, apply a lightconstricting cloth or other band on thebitten limb, 2 to 4 inches (5 to 10 cm) fromthe bite and between bite and heart.Make sure it is not as tight as a tourni-quet. It should be easy to insert a fingerunder the band. Loosen it if swellingoccurs. Apply suction at the wound forat least 3/4 of an hour by mouth (if nomouth sores), or with a snake bite kit, butagain, only if medical assistance is sev-eral hours away.

The causes of human death fromrattlesnake venom are varied, but usu-ally occur from extended hypotensionand cardiopulmonary arrest. Usuallywithin a few minutes after beingstruck the victim will experience painand swelling at the wound site.


The greatest economic loss to humansfrom rattlesnakes comes from thenumber of domestic livestock and petsthat are killed. Horses and cattle aremost frequently struck in the headwhile grazing. Some have claimedthat rattlesnakes benefit ranchers bythe number of rodents they eat, butcurrent predator-prey theory dis-counts this. It is very doubtful thatsnakes have much effect on the densityof rodents.

The commercial value of rattlesnakesconsists of the venom, rattles, skinsand, to a limited degree, the meat.

AcknowledgmentsFigures 1 through 3 by Emily Oseas Routman.

Figures 4 and 5 by Jill Sack Johnson.

For AdditionalInformationDunkle, T. 1981. A perfect serpent. Science 81

2:30-35.

Duvall, D., M. B. King, and K. J. Gutzwiller.1985. Behavioral ecology and ethology ofthe prairie rattlesnake. Natl. Geogr. Res.1:80-111.

Dolbeer, R. A., N. R. Holler, and D. W.Hawthorne. 1994. Identification and controlof wildlife damage. Pages 474-506 in T. A.Bookhout ed. Research and managementtechniques for wildlife and habitats. TheWildl. Soc. Bethesda, Maryland.

Kilmon, J., and H. Shelton. 1981. Rattlesnakes inAmerica. Shelton Press, Sweetwater, Texas.234 pp.

Klauber, L. M. 1972. Rattlesnakes: their habits, lifehistories, and influence on mankind, 2 vols.Univ. California Press, Berkeley. 1533 pp.

Klauber, L. M. 1982. Rattlesnakes: their habitats,life histories, and influence on mankind.Abridged by K. H. McClung. Univ.California Press, Berkeley. 350 pp.

Knight, J. E. 1986. A humane method forremoving snakes from dwellings. Wildl. Soc.Bull. 14:301-303.

Marsh, R. E., and W. E. Howard. 1982.Vertebrate pests. Pages 791-861 in A. Maillis,ed. Handbook of pest control, 6th ed.Franzak and Foster Co., Cleveland, Ohio.1001 pp.

Pinney, R. 1981. The snake book. Doubleday &Co., New York. 248 pp.

San Julian, G. J., and D. K. Woodward. 1986.What you wanted to know about all youever heard concerning snake repellents.Proc. Eastern Wildl. Damage Control Conf.2:243-248.

Seigle, R. A., J. T. Collins, and S. S. Novak. 1987.Snakes: ecology and evolutionary biology.Macmillan Publ. Co., New York. 529 pp.

Story, K. 1987. Snakes: separating factfrom fantasy. Pest Control Technol.15(11):54,55,58,60.

Wade, D. A., and J. E. Bowns. 1982. Proceduresfor evaluating predation on livestock andwildlife. Bull. No. B-1429, Texas A & MUniv., College Station. 42 pp.


James F. FowlerWildlife SpecialistLouisiana Cooperative



Jimmy L. AveryArea Aquaculture AgentLouisiana Cooperative



TURTLES

Fig. 1. Eastern box turtle, Terrapene carolina


Exclusion

Generally not practical. Small areascan be fenced.

Cultural Methods

Routine drainage of fish pondsgenerally results in lowerpopulations.

Keep levees mowed to makeaquaculture ponds less attractive toturtles.

Drain rice irrigation systems duringlate summer to reduce populationsprior to spring planting.

Repellents


Toxicants


Fumigants


Fishing

Hook and line with bait.

Snag pole.

Trapping

Can be effective at certain times andplaces.

Shooting

Can be used to reduce populations ofturtles. Check for local restrictionsbefore discharging firearms. Somestates prohibit the shooting ofturtles in ponds and lakes.





Identification and Range

Turtles occur on all continents exceptAntarctica. Over 240 species occurworldwide but turtles are most abun-dant in eastern North America. Mostturtles have good field characteristicsthat are visible and can be easily iden-tified. Some species, however, requireclose examination of the shields on theplastron (underside shell) for apositive identification.

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Any permanent body of water is apotential home for turtles. Some spe-cies will also tolerate brackish water,but the sea turtles are the only truesaltwater species.

Unlike most other turtles, includingsoft-shells, snapping turtles rarelybask. Turtles feed on a combination ofplant and animal material thatincludes items such as aquatic weeds,crayfish, carrion, insects, fish, andother small organisms. The diet ofsnapping turtles, however, usuallyincludes a relatively high proportion offish. They are relatively aggressivepredators, occasionally known to takefish off fish stringers.

All turtles reproduce by laying eggs inearly spring. Hatching begins in latesummer and extends into the fall,depending on summer temperaturesassociated with the climate of therange. During winter, turtles usuallybury themselves in soft mud or sand inshallow water with only the eyes andsnout exposed.

Turtles are easy prey for a number ofpredator species such as alligators,otters, raccoons, and bears. Humansare probably the greatest threat toturtle populations, particularly for themost commercial species, such assnappers and soft-shells.

Damage

Turtles are seldom a pest to people.Turtles are very beneficial and of eco-nomic importance, except in certainareas such as waterfowl sanctuaries,aquaculture facilities, and rice fields inthe south. Indiscriminate destructionof turtles is strongly discouraged, andevery effort should be made to ensurethat local populations are not extermi-nated unless it can be clearly demon-strated that they are undesirable.

Some species of pond and marshturtles are occasional economic pestsin rice fields in the south. Their feeding

activity on young rice often results insignificant yield reductions in localareas.

In farm ponds, turtles undoubtedlycompete with fish for natural foodsources such as crayfish and insects.Turtles, however, are valuable becausethey kill diseased and weakened fish,and clean up dead or decaying animalmatter.

In commercial aquaculture productionponds, turtles can eat fish that arebeing grown. They also eat fish food.Aquaculture ponds are not the pre-ferred habitat of turtles, however. Theheavy clay soils required for pond con-struction are not conducive to theturtles’ laying of eggs.

Legal Status

Most turtles are not protected by statelaws. Licenses usually are required forcommercial fishing and sale of turtles.Before taking turtles, contact a statewildlife or conservation agency repre-sentative for legal status.

There were two turtles listed by theUS Fish and Wildlife Service as endan-gered or threatened species as ofDecember 1992. The desert tortoisewas listed as threatened everywhereexcept for a population in Arizona. Itshistoric range is Arizona, California,Nevada, and Utah. The gopher tor-toise was listed as threatened wher-ever found west of the Mobile andTombigbee rivers in Alabama, Missis-sippi, and Louisiana. Its historic rangeis Alabama, Florida, Georgia, Louisi-ana, Mississippi, and South Carolina.

Five freshwater turtles were listed bythe US Fish and Wildlife Service asendangered or threatened species as ofDecember 1992. The Alabama red-bellied turtle and the flattened muskturtle were listed as endangered andthreatened, respectively. Alabama isthe historic range of both species. Theringed sawback turtle is threatened inits historic range of Louisiana andMississippi. The yellow-blotched mapturtle is threatened in its historic rangeof Mississippi. The Plymouth red-bellied turtle is endangered in its his-toric range of Massachusetts.

Additional species under reviewinclude the alligator snapping turtle,bog turtles, and the western tortoises.


Cultural Methods

The best control for box, pond, andmarsh turtles in rice fields is to drainirrigation canals and fallow fields dur-ing winter months. Without a perma-nent water source year-round, thesespecies do not reach large enoughpopulations to become a serious eco-nomic problem.

Ponds that are used for the productionof channel catfish or other finfish areroutinely harvested by seining. Theseining process will also captureturtles. Farmers can control turtlepopulations by moving these capturedturtles to their natural habitats.

Repellents, Toxicants, andFumigants


Trapping

Since turtles generally are not a pest topeople, control measures are limitedprimarily to trapping. Trapping can beused quite effectively to reduce localpopulations of these species wheredamage occurs.

The best place to trap turtles is in thequiet water areas of streams andponds, or in the shallow water oflakes. Soft-bottom areas near aquaticvegetation are excellent spots.

The best seasons for trapping arespring, summer, and early fall. Mostturtles hibernate through the winter,except in the extreme south, and donot feed, making trapping ineffective.Methods of trapping are described forvarious types of turtles in the follow-ing sections.

Traps should be baited with fresh fishor red meat. Catfish heads and cutcarp are regarded as two of the bestbaits available for trapping turtles.Baits should be suspended in traps ona bait hook or placed in bait containers

Isometric view

Horizontal section through throat

Vertical section through throat

Fig. 2. Hoop net turtle trap.

Throat

Front hoop

Rear hoop

Stretcher

Stretcher

for maximum effectiveness. In areaswhere turtle populations are high, it isoften necessary to check traps two orthree times per day and add fresh bait,since turtles are capable of consuminglarge quantities of bait rather quickly.

Snapping and Soft-Shell Turtles.While snapping turtles are in hiberna-tion, they often can be taken in quanti-ties from spring holes and old muskratholes, under old logs, and in soft bot-toms of waterways. Turtle collectorsrely on their hunting instincts andexperience to locate hibernatingturtles. When one is found, it pays toexplore the surrounding area carefullybecause snappers often hibernatetogether. The method for capture,known as “noodling” or “snagging,”requires a stout hook. One end of aniron rod is bent to form a hook andsharpened; the other end of the rod isused for probing into the mud or soilto locate the turtles. The hunter probesabout in the mud bottom until a turtleis located (which feels much like apiece of wood) and then pulls it outwith the hook. Turtles are inactive dur-ing the winter and offer little resistanceto capture, although the landing oflarge ones may be difficult even forexperienced hunters.

Snappers and soft-shelled turtles aresometimes taken on set lines baitedwith cut fish or other fresh meat. Onerecommended device is made by tying4 or 5 feet (1.2 or 1.5 m) of line to astout flexible pole, 6 to 8 feet (1.8 to 2.4m) long. About 12 inches (30.5 cm) ofNo. 16 steel wire is placed between theline and the hook, preferably a stouthook about 1 inch (2.5 cm) acrossbetween barb and shaft. The end of thepole is pushed into the bank farenough to make it secure at an anglethat will hold the bait a few inches(cm) above the bottom.

Snappers and soft-shelled turtles mayalso be taken readily in baited fyke orhoop nets (Fig. 2). These barrel-shapedtraps may sometimes be purchased onthe market or made from 3-inch (7.6-cm) square mesh of No. 24 nylon seinetwine. The trap should be 4 to 6 feet(1.2 to 1.8 m) long from front to backhoop. The three to five hoops per trap

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Fig. 3. Sink box turtle trap.

Fig. 4. Sink box turtle trap with pivotal boards.

3/8" iron rod

11"

12"

48"

22"

24"

48"

8"

should be 30 inches (76 cm) in diam-eter, made of wood or 6-gauge steelwire with welded joints. The funnel-shaped mouth should be 18 inches (46cm) deep from the front hoop to theopening inside. The entrance openingof the funnel should be 1 inch x 20inches (2.5 x 51 cm). The corners of theopening are tied by twine to themiddle hoop. The rear or “box” endmay be closed with a purse string.After the hoops have been installed,the net should be treated with a pre-servative of tanbark, cooper oleate, tar,or asphalt. To keep the trap extended,stretchers of wood or steel wire, about9 gauge or larger, are fastened alongeach side.

Coarse mesh poultry wire may be sub-stituted for the twine. If this is done,the frame will be approximately 30inches (76 cm) square. The shape anddimensions of the entrance as specifiedshould be the same in all traps, as it iseasily negotiated by the turtles. Thedimensions of the trap may be alteredfor ease of transportation. A door maybe installed in the top to facilitate bait-ing and removal of turtles. Entrancefunnels may be placed on each end ifdesired.

Fyke or hoop turtle traps should be setwith the tops of the hoops just out ofthe water. This will permit the turtlesto obtain air and lessen their strugglesto escape, and will enable other turtlesto enter the trap more freely. It is nec-essary to set traps this way if the tur-tles are to be taken alive. Traps set instreams must be anchored. If the wateris too deep for the top of the trap to beout of the water, short logs can belashed to each side to float the trap.Turtles enter more readily when themouth of the trap is set downstream.

Box, Pond, and Marsh Turtles.Because of their habits, these speciesmust be captured with methods differ-ent from those for snapping and soft-shelled turtles. They cannot be taken innumbers during the winter, like snap-pers, because they do not congregatein their hibernating places. In the sum-mer some species are gregarious,crowding together in numbers on pro-jecting logs and banks. By taking

advantage of this fact, these baskingspecies may be taken by trapping in abox sunk in a place the turtles areusing. The turtles crawl up onto thetop of the box to bask in the sun, andmany of them fall into the trap (Fig. 3).

The top frame of the box may be con-structed from discarded telephonepoles, imperfect ties, or logs about 8inches (20 cm) in diameter. Old naturalunpainted wood is preferred. The logsare mitered at each end to fit together,and the inside enclosure made to mea-sure 2 to 3 feet (61 to 91 cm) square.About half of each log from the topcenter to the inside under center islined with zinc or galvanized metal.Turtles that have dropped into the trapare unable to climb over the zinc orgalvanized metal covering. From theoutside water edge to the top of eachlog, cleats can be nailed or the logsmade rough, so turtles can easily climbon top. Galvanized mesh wire can befastened to the logs with staples,hooks, or wire to form a wire basketfitting the opening between the logs.One-inch (2.5-cm) mesh is about rightif all sizes of turtles are to be trapped.If only larger specimens are sought,however, a 3-inch (7.6-cm) mesh canbe used. The trap should be fastenedto a stump or some other permanentanchor.

Some trappers prefer to use bait;others leave the traps unbaited. For thecapture of snapping and soft-shelledturtles, the trap can be modified byinstalling funnel-like entrances on oneor two sides as described for the hooptraps.

Another type of trap consists of a boxwith an inclined board leading up to it.The turtles climb up on the board tobask and drop off into the box. Figure4 shows the same trap with pivotalboards placed so that turtles crawlingout on the boards overbalance on theterminal end and are dropped into thebox.

Shooting

In some states, shooting can also beused as a means of reducing popula-tions in ponds and lakes. This tech-nique, however, is not very effective.

Economics of Damageand Control

Three groups of turtles are of eco-nomic importance in North America.They include the snapping turtles; thebox, pond, and marsh turtles; and thesoft-shelled turtles. Snapping turtlesare trapped for human consumptionand are being considered for aqua-culture. Red-eared turtles are culturedfor the foreign pet trade. Soft-shellturtles are also trapped for humanconsumption.

Damage is typically of little economicconcern, but may be a problem in riceand aquacultural production.

Acknowledgments

Figure 1 from C. W. Schwartz: WildlifeDrawings (1980), Missouri Department ofConservation, Jefferson City.

Figures 2 through 4 from Wildlife Damage ControlHandbook (1969), Kansas State University,Manhattan. Adapted by Emily Oseas Routman.


Conant, R., and J. T. Collins. 1991. A field guideto reptiles and amphibians: eastern andcentral North America. 3d ed. HoughtonMifflin Co. Boston. 450 pp.

Ernst, C. H., and R. W. Barbour. 1972. Turtles ofthe United States. Univ. Kentucky Press,Lexington. 347 pp.

Stebbens, R. L. 1985. A field guide to westernreptiles and amphibians. 2d ed. HoughtonMifflin Co., Boston. 279 pp.


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