IntroductionA neotropical folivore, the green iguana (Iguana iguana)

is exotic to southern Florida, where it has few known

predators (Kryskyo et al. 2007) and limiting factors are

poorly understood. At high densities (see Meshaka et al.

2007), this reptile may threaten native wildlife (Smith et

al. 2006), including the imperiled Miami blue butterfly

(Cyclargus thomasi bethunebakeri) (FFWCC 2010).

Gravid female iguanas shun densely shaded areas for

nesting and move to more open settings to nest (Bock

and Rand 1989). Thus, hurricanes may create or

maintain clearings favorable for iguana nesting. Here I

suggest that Hurricane Wilma, the most severe Florida

Keys hurricane since 1965 (Kasper 2007), was a

catalyst for iguana proliferation. Until my study, the

distribution of this reptile and its sympatry with the Miami

blue in the Key West National Wildlife Refuge

(KWNWWR) were unknown.

Methods• Searched for iguana burrows and tracks on 14

islands, 12 with uplands, in the KWNWR during the

iguana nesting season (Feb-March)

• Trapped (42 trap nights) iguanas on 1 island in the

Marquesas Keys

• Necropsied captured females to obtain clutch sizes

•Results• Iguanas present on 12 islands distributed over 28

linear km

• All iguana burrows were in remnants of once- large

clearings created by Hurricane Wilma

• Burrow density varied greatly among islands: highest

on east Man Key (31 burrows in < 0.2 upland ha)

• Largest number of burrows (n = 62) on Long Beach

(Marquesas) despite only a partial search

• Gravid females (n=3) averaged 55.6 eggs (range =

42-61)

• Iguanas were syntopic with the Miami blue and

nested in all 8 areas harboring the butterfly

DiscussionIn the KWNWR, Hurricane Wilma transformed what had

once been a densely vegetated setting with little suitable

iguana nesting habitat (Fig. 1) into an open landscape

(Fig. 2) with an abundance of it. More than 5 years after

the storm virtually all iguana burrows were found in

remnants of clearings known to have been created by

Hurricane Wilma (Wilmers pers obs.), suggesting that

this hurricane was and continues to be an important

ConclusionsYou can, of course, start your conclusions in column #3 if

your results section is “data light.”

Conclusions should not be mere reminders of your

results. Instead, you want to guide the reader through what

you have concluded from the results. What is the broader

significance? Would anyone be mildly surprised? Why

should anyone care? This section should refer back,

explicitly, to the “burning issue” mentioned in the

introduction. If you didn’t mention a burning issue in the

introduction, go back and fix that -- your poster should have

made a good case for why this experiment was worthwhile.

Tom Wilmers, Florida Keys National Wildlife Refuges, Big Pine Key, FL 33043

Green Iguana Proliferation in the Key West National Wildlife Refuge: A Hurricane

By-product and a Threat to the Imperiled Miami Blue Butterfly?

No panacea: some imperfect measures:

• Wait for another hurricane of Wilma’s magnitude

--live vegetation will be limited and iguana numbers likely

greatly reduced, concentrating survivors and increasing the

effectiveness of intensive trapping and nest destruction

• Trap nesting females February-March

• Find and destroy nests

• Collect stomach contents from 50 trapped iguanas to

determine if blackbead is commonly eaten

In the KWNWR, the Miami blue (left), one of the rarest

butterflies in the world, lays eggs (right) only on

blackbead leaves or buds. Iguana consumption of

blackbead is unconfirmed but merits investigation.

Literature Cited Bock, B.C. and A.S. Rand. 1989. Factors influencing nesting synchrony

and hatching success at a green iguana aggregation in Panama. Copeia

1989 (4): 978-986.

Cannon, P., T. Wilmers, and K. Lyons. 2010. Discovery of the imperiled

Miami Blue Butterfly on islands in the Florida Keys National Wildlife

Refuges, Monroe County. Southeastern Naturalist 9: 847-953.

Florida Fish and Wildlife Conservation Commission 2010. Miami blue

butterfly management plan. FFWCC, Tallahassee, FL. 41 pp.

Kasper, K.N. 2007. Hurricane Wilma in the Florida Keys. National

Oceanic and Atmospheric Administration (NOAA)/National Weather

Service (NWS) Weather Forecast Office (WFO) Key West, Florida.

Krysko,K.M., E.M. Enge, J.C. Donlan, and E.M Golden. 2007.

Distribution, natural history and impacts of the introduced green iguana

(Iguana iguana) in Florida. Iguana 14:142-151.

Meshaka, W.E., H.T. Smith, E. G., and J.A. Moore. 2007. Green iguanas

(Iguana iguana): The unintended consequence of sound wildlife

management practices in a south Florida park. Herpetological

Conservation and Biology 2:149-156.

Rand, S.A. B. Dugan, and D. Vianda. The diet of a generalized folivore,

Iguana iguana in Panama. J. Herpetology 26:211-224.

Smith, H.T., W.E. Meshaka, and R. Engeman. 2006. Raccoon predation

as a potential limiting factor in the success of the green iguana in

southern Florida. Journal of Kansas Herpetology 20:7-8.

Webster, P. J., G. J. Holland, J. A. Curry, and H.-R. Chang. 2006.

Changes in tropical cyclone number, duration, and intensity in a warming

environment. Science 16 :1844-1846.

Distribution of green iguanas in the Key West National Wildlife

Refuge, 2011. Yellow markers indicate islands where iguana

burrows were found.

Green Iguanas and the Miami blue butterfly

In the KWNWR, the Miami blue lays eggs only on blackbead

(Pithecellobium keyense) leaves and buds (Cannon et al. 2010). In

their native range, green iguanas eat a variety of plants but may

consume whatever plant is most abundant and common (Rand et al.

1990). Blackbead is the most common woody plant on 6 of the 8

uplands that harbor the Miami blue (Wilmers pers obs.). Whether

green iguana eat blackbead leaves is unconfirmed and merits

investigation. If it does eat blackbead, Miami blue eggs and larvae

would be consumed. Miami blue numbers greatly fluctuate (Cannon

et al. 2010) and at low numbers, iguana consumption of the

butterfly’s eggs could lead to extirpation on one or more of the 8

islands that harbor the butterfly. The iguana population may

increase unchecked in KWNWR until some a limiting factor is

reached. Of great concern is a future hurricane of Wilma’s

magnitude once again killing most of the blackbead, concentrating

the butterfly and the reptile in the small patches that remain. The

number and severity of hurricanes is expected to increase due to

global warming (Webster et al. 2006).

Why iguana eradication is likely an exercise in futility:• The size and remoteness of the occupied areas

• Iguanas swim well and move between islands.

• The largest island in the Marquesas is > 8 km long and thus is a

reservoir for replenishment of animals removed from smaller

islands

• The reptile’s high reproductive rate and a lack of native predators

• Trapping constraints: 1. inability to capture most age classes; 2.

trap-shyness; 3. state law mandates checking traps every 24

hours but vagaries of weather preclude this; 4. dense, dead

vegetation is mixed with live vegetation in the coastal strand; 5.

enormous manpower needed even if traps were effective.

Figures 1,2. The absence (left) and abundance (right) of

iguana nesting habitat on Boca Grande Key before and 1

month after Hurricane Wilma. Notice the lone palm tree.

East Man Key 2 months (left) after Hurricane Wilma and the

same area 5 years later (right). Today, iguana nesting in the

KWNWR is limited largely to remnant clearings created by

this hurricane.

factor for the reptile’s proliferation in the KWNWR. With few

known iguana predators in Florida (Smith et al. 2006), as the

vegetation grew after the hurricane the abundance of suitable

nesting areas likely allowed the iguana population to grow

exponentially.

The green iguana’s origin in the KWNWR is unknown, but given

their now wide distribution, it is untenable that they arrived at all

islands as waifs transported by the hurricane. Instead, as their

population expanded in the KWNWR, individuals from a source

population likely swam to other islands, as occurs in their native

range (see Bock and Rand 1998).

The captured gravid females (left) were large. Mean clutch

size was 55.6 eggs. Green iguana burrows (right) on east

Man Key.