modeling the effects of trophy selection and...

Modeling the Effects of Trophy Selection andEnvironmental Disturbance on a SimulatedPopulation of African LionsKARYL L. WHITMAN,∗†§‡ ANTHONY M. STARFIELD,† HENLEY QUADLING,†‡ ANDCRAIG PACKER††Department of Ecology, Evolution & Behavior, University of Minnesota, 1987 Upper Buford Circle, St. Paul, MN 55108, U.S.A.§Porini consulting, 18527 73rd Avenue NE, Kenmore, WA 98028, U.S.A.‡D4D Technologies, 630 International Parkway #150, Richardson, TX 75081, U.S.A.

Abstract: Tanzania is a premier destination for trophy hunting of African lions (Panthera leo) and is hometo the most extensive long-term study of unhunted lions. Thus, it provides a unique opportunity to apply datafrom a long-term field study to a conservation dilemma: How can a trophy-hunted species whose reproductivesuccess is closely tied to social stability be harvested sustainably? We used an individually based, spatiallyexplicit, stochastic model, parameterized with nearly 40 years of behavioral and demographic data on lions inthe Serengeti, to examine the separate effects of trophy selection and environmental disturbance on the viabilityof a simulated lion population in response to annual harvesting. Female population size was sensitive to theharvesting of young males (≥3 years), whereas hunting represented a relatively trivial threat to populationviability when the harvest was restricted to mature males (≥6 years). Overall model performance was robustto environmental disturbance and to errors in age assessment based on nose coloration as an index used toage potential trophies. Introducing an environmental disturbance did not eliminate the capacity to maintaina viable breeding population when harvesting only older males, and initially depleted populations recoveredwithin 15–25 years after the disturbance to levels comparable to hunted populations that did not experience acatastrophic event. These results are consistent with empirical observations of lion resilience to environmentalstochasticity.

Keywords: lion harvest, Panthera leo, population model, population viability, sustainable use, Serengeti, trophyhunting

Modelacion de los Efectos de la Seleccion de Presas y de la Perturbacion Ambiental en una Poblacion Simulada deLeones Africanos

Resumen: Tanzania es un destino preferido para la caza deportiva de leones Africanos (Panthera leo) yes el hogar del estudio de largo plazo mas extensivo de leones no cazados. Por lo tanto, proporciona unaoportunidad unica para aplicar datos de un estudio de largo plazo a un dilema de conservacion: Comose puede aprovechar sustentablemente a una especie cinegetica cuyo exito reproductivo esta estrechamenteligado a la estabilidad social? Utilizamos un modelo estocastico, espacialmente explıcito y basado en individuoscon datos conductuales y demograficos, de casi 40 anos, de leones en el Serengeti, para examinar los efectosseparados de la seleccion de trofeos y la perturbacion ambiental sobre la viabilidad de una poblacion simuladade leones en respuesta a la cacerıa anual. El tamano de la poblacion de hembras fue sensible a la cacerıade machos jovenes (≥3 anos), mientras que la cacerıa represento una amenaza relativamente trivial a laviabilidad poblacional cuando la cacerıa se restringio a los machos maduros (≥6 anos). El funcionamientogeneral del modelo fue robusto a la perturbacion ambiental y a errores en la estimacion de edades con base

∗email [email protected] submitted May 18, 2006; revised manuscript accepted February 12, 2007

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Conservation Biology Volume 21, No. 3, 591–601C©2007 Society for Conservation BiologyDOI: 10.1111/j.1523-1739.2007.00700.x

592 Harvesting African Lions Whitman et al.

en la coloracion de la nariz como ındice para estimar la edad de trofeos potenciales. La introduccion de laperturbacion ambiental no elimino la capacidad para mantener una poblacion reproductiva viable cuandose cazaba solo a machos maduros, y las poblaciones inicialmente reducidas se recuperaron entre 15 y 25 anosdespues de la perturbacion alcanzando niveles comparables a poblaciones cazadas que no experimentaronun evento catastrofico. Estos resultados son consistentes con observaciones empıricas de la resiliencia de leonesa la estocacidad ambiental.

Palabras Clave: cacerıa deportiva, cosecha de leones modelo poblacional, Panthera leo, Serengeti, viabilidadpoblacional, uso sustentable

Introduction

One of the most important factors for the effective man-agement of a species is a thorough understanding of life-history and behavioral characteristics that are integralto its reproductive success. Behavioral ecological stud-ies therefore play a critical role in conservation sciencebecause they define such behavior and would not be pos-sible without long-term demographic records or detailedobservations of individuals (Caro & Durant 1995). Nev-ertheless, long-term data sets encompassing several gen-erations are uncommon, even more so for species thatexhibit socially complex behaviors and that are huntedby humans for sport. Removing the primary breeders ina population can disrupt social organization and hamperreproduction and recruitment, thus making it difficult topredict the potential impact of commercial hunting. Long-term studies have been conducted on African lions in theSerengeti for nearly 40 years providing precise estimatesfor demographic and behavioral parameters in a detailedsimulation model that can predict the likely impact ofmanagement strategies (Whitman et al. 2004).

Large carnivores have declined in abundance and theirranges have diminished substantially throughout Africa(Frank & Woodroffe 2001; Woodroffe 2001). As rising hu-man populations encroach on wildlife habitat, carnivoresare becoming increasingly vulnerable to human-wildlifeconflict, especially adjacent to protected areas in Africa(Woodroffe & Ginsberg 1998; Harcourt et al. 2001). Hu-man population size is a significant threat to species vi-ability (Herremans & Herremans-Tonnoeyr 2000; Lucket al. 2004) and a substantial proportion of carnivoremortality is directly attributable to anthropogenic factors(Woodroffe & Ginsberg 1998). Retaliation from farmersover livestock depredation is a leading cause of carnivoremortality (Ogada et al. 2003; Treves & Karanth 2003).

Based largely on educated guesses from scientific au-thorities (Chardonnet 2002; Bauer & Van Der Merwe2004) and extrapolation from known population densi-ties combined with catch-per-unit effort estimates fromtrophy hunters (Chardonnet 2002), the number of Africanlions (Panthera leo) is estimated be between 16,500 and47,000 individuals. Earlier estimates of lion numbers are

too crude to evaluate the extent to which lion numbershave declined over the past 20–30 years, but suitable habi-tat has declined, and lions no longer occupy the full extentof their historic range (Nowell & Jackson 1996; Chardon-net 2002), particularly in unprotected areas (Bauer & VanDer Merwe 2004).

Early twentieth-century hunting expeditions removedlarge numbers of African lions, as did the European live-stock ranchers that followed. Many of the historic hunt-ing grounds used by white big game hunters and settlershave since acquired some degree of protection (MacKen-zie 1988), and lion hunting has ceased altogether in manyareas. Human encroachment, reduced prey base, and di-rect human-caused mortality (e.g., problem-animal con-trol) are presumably responsible for recent declines inlion abundance and distribution (Woodroffe & Ginsberg1998; Harcourt et al. 2001; Chardonnet 2002). In Kenyafor example, lion numbers have continued to decline out-side protected areas (Ogutu et al. 2005; L. Frank, personalcommunication 2005) despite a ban on trophy hunting fornearly 30 years.

Lion populations are particularly vulnerable to extir-pation when population sinks and edge effects are cre-ated by large-scale human activity (Woodroffe & Ginsberg1998). In areas where humans and lions exist in closeproximity, lions pose a persistent threat to rural peopleand their livelihood (Frank 1998; Packer et al. 2005a).Because lions will readily scavenge, they are easily poi-soned and trapped by poachers using long-line snares. Inaddition only a few protected areas are large enough toprovide adequate amounts of suitable habitat to maintainviable populations (Harcourt et al. 2001; Loveridge et al.2001). Villagers and governments regularly kill lions thatleave protected areas, potentially creating a vacuum thatdraws more animals from the “source” populations in theprotected areas.

Increasing human demands for land have reduced suit-able wildlife habitat and challenged developing countriesto find alternative resource-management strategies. Tro-phy hunting by foreign tourists (Kock 1995; Lewis &Alpert 1997) brings money into areas that are unsuitablefor photographic tourism and provides an economic in-centive for locals to conserve wildlife (Child & Child 1990;Eltringham 1994). Nevertheless, profit-oriented, short-

Conservation BiologyVolume 21, No. 3, June 2007

Whitman et al. Harvesting African Lions 593

term gains from trophy hunting can increase the risk ofoverexploitation (Lavigne et al. 1996).

Trophy hunting of lions is a multimillion dollar industryin sub-Saharan Africa (Creel & Creel 1997; Overton, 1998;Whitman 2002). Tourists hunt lions in 10 African coun-tries: Botswana, Burkina Faso, Central African Republic,Chad, Mozambique, Namibia, Republic of South Africa,Tanzania, Zambia, and Zimbabwe. Tanzania yields about17% of the top-10 lions reported to the Safari Club Interna-tional (SCI) and is the most expensive country in which tohunt lions (Whitman 2002). An average 21-day safari costsover $75,000. In Tanzania lions contribute approximately10–13% of trophy fees despite accounting for only 2–4%of the total number of animals taken in any given year(PAWM 1995; Broomhead 1997a,b). A lion quota oftenpromotes use of less-marketable species (Creel & Creel1997). The temporary ban on lion hunting in Botswanabetween 2001–2005 is estimated to have cost the govern-ment over $4.3 million/year (McGreal 2001).

Although the sport-hunting industry generates signifi-cant revenue and makes a positive contribution to the na-tional economy, a lack of transparency in hunting-blockallocation, arbitrary division of hunting concessions andconcomitant increases in quotas, and unethical behav-ior by professional hunters all contribute to the risk ofoverhunting (Overton 1998; Whitman 2002; Baldus &Cauldwell 2004). Given that lion populations may be par-ticularly sensitive to the removal of resident males (e.g.,Packer et al. 1988; Yamazaki 1996; Whitman et al. 2004),questions have arisen concerning the sustainability andutility of trophy hunting as a conservation tool. Legalquotas are based on guess work (Severre 1995) and es-tablishing a reasonable offtake presumes knowledge of apopulation that is often unavailable. Nevertheless, Whit-man et al. (2004) recently demonstrated that lion huntingcan be biologically sustainable without the use of quotasby applying an age-based criterion to trophy selection.

In a previous study we estimated the effects of trophyhunting on long-term population viability with varyingharvesting strategies for a simulated population (Whit-man et al. 2004). We concluded that harvesting ≥5- to6-year-old males has the least impact on the populationand produces the greatest cumulative number and mostconsistent “crop” of high-quality males over time and runsvirtually no risk of overhunting. Our data also showedthat nose color can be used to estimate the age of po-tential trophy males before they are shot. We parame-terized the model based on empirical data from nearly40 years of ongoing behavioral and demographic studiesconducted in the Serengeti (Packer et al. 1988; Packeret al. 1998; Packer et al. 2001). The lions’ complex so-cial behavior plays a significant role in cub survival, prideformation, and recruitment (Packer 2000; Packer & Pusey1983a,b, 1984), and infanticide by incoming males greatlyincreases the risk of extinction in simulated hunted pop-ulations (Whitman et al. 2004).

Although we demonstrated that sustainable hunting oflions could be achieved by removing only older individ-uals (Whitman et al. 2004), we did not test whether thisstrategy is sensitive to environmental effects. The impactof environmental stochasticity was homogenized in ouroriginal model by averaging the year-to-year variation inthe underlying data despite a catastrophic die-off in 1993–1994 from a virulent canine distemper epidemic in ourstudy population (Roelke-Parker et al. 1996). Social be-havior of some animals can influence the impact of eco-logical fluctuations even when environmental conditionsare notably severe (Vucetich et al. 1997; Grimm et al.2003). To further examine the effects of environmentalperturbation, we examined the robustness of our modelagainst two additional influences: (1) the importance ofenvironmental stochasticity, by imposing an ecologicaldisaster before the onset of annual harvesting and (2) theinevitable inaccuracies of age estimation when it is basedon a statistical correlate of age.

Lion-Hunting Policies in Tanzania

In Tanzania trophy hunting takes place on approximately250,000 km2 of government-owned land in game re-serves, open areas, wildlife management areas, and game-controlled areas. Hunting areas are divided into approxi-mately 141 concessions used by approximately 42 sepa-rate outfitters (Wildlife Division 2003). Imprecise bound-aries of many of the hunting concessions preclude anaccurate measurement of the area of each, but in 1992the average hunting block was approximately 1370 km2

(Leader-Williams et al. 1996). Today the average size islikely somewhat smaller because many areas have beensubdivided since 1992. Trophy hunting of lions is limitedto males in Tanzania. In 1996 all but 2 of 131 concessionshad a lion quota for their area, and the average quota forthose areas was 3.9 lions/concession (range 1–12, n =129) (Broomhead 1997a). Less than 50% of the total lionquota is met each year (236 lions out of a quota of 516were shot in 1995: Broomhead 1997a,b). If we conser-vatively estimate that 10,000–15,000 lions reside in thewhole of Tanzania, an annual harvest of about 200 lionsrepresents <2% of the total population.

The Wildlife Division of Tanzania mandates that for-eign tourists must use a licensed professional hunter asa guide and pay for a 21-day safari to shoot a lion (re-gardless of the success or actual length of the safari). Thegovernment sets a flat rate of $850/day/client and a tro-phy fee of $2000 (PAWM 1995). Nevertheless, huntingcompanies charge significantly higher rates for conces-sions that repute to have “quality” lions such as the re-serves surrounding Serengeti National Park. In these ar-eas daily rates may reach $2800/day/client, trophy feesmay be as much as $5500, and companies may add a



5–25% surcharge to the trophy fee that goes to antipoach-ing and community development programs (Whitman2002). Approximately 9% of all trophy fees paid to theWildlife Division are supposed to be disbursed to lo-cal communities through their district councils (Leader-Williams et al. 1996, but see Overton 1998; Leader-Williams & Hutton 2005). At the minimum a one-person21-day safari costs between $30,000–50,000, excludingtransportation, taxidermy, preparation and shipping oftrophies, nonhunting observers, and gratuities (Whitman2002). Baiting lions by means of a carcass is unofficiallypermitted by order of the Director of Wildlife and shoot-ing may take place only between one-half hour beforesunrise and sunset (Whitman 2002).

The Model

We developed a comprehensive, spatially explicit modelthat tracks individuals through time (Quadling & Starfield2002; Whitman et al. 2004). Each territory or “pride” con-sists of females and their dependent offspring that arespatially linked within the population. To represent theworst-case scenario, we modeled the impact of trophyhunting on a closed population. Life-history behavior anddemographic rates used in the model are defined by ageclass (cubs <6 months, cubs 6–12 months, cubs 13–24months, subadult males and females, adult males and fe-males) based on long-term studies of an unhunted popu-lation of lions in Serengeti National Park and NgorongoroCrater (Packer et al. 1988; Packer et al. 1998; Packer etal. 2001). Females may only produce cubs between 3–13years of age, and they breed only when their offspringfrom a previous litter reach 2 years of age or if an entirelitter perishes. Males are classified as subadults, nomads,or residents. Singleton males may join other solitary malesor coalitions of two. Resident males may reside in up tothree prides at one time. Nomadic and subadult males donot breed, but may move freely between prides a speci-fied number of times per time step. A competition matrix(Starfield et al. 1981) based on social status, collective age,and coalition size determines whether males encounter-ing each other fight, and subsequent survival if they do.An age-specific probability of infanticide following thetakeover of prides by males determines cub survivorship.

At each time step (6 months), the model assesses in-dividual survival, updates ages of survivors, allows fe-males to produce cubs, categorizes 2-year-old males ineach pride into subadult male groups, advances 3-year-oldmales into nomadic groups, and either permits subadultfemales to join a pride or removes them from the pop-ulation. The model determines litter size for each eligi-ble female with a random number from a distribution.Survivorship depends on observed survival rates for in-dividuals of similar age, sex, and social status. Female re-

cruitment into natal prides is contingent upon a specifiedmaximum number of females (that can be temporarilyexceeded by no more than 2 females) for each pride.Subadult females that do not join their natal prides maysearch for vacant territories or are eliminated from themodel if none are available. The output of average age ofresident males, size range of male coalitions and subadultcohorts, and male:female:cub ratios of a simulated pop-ulation at “equilibrium” realistically portrayed observedpopulations (Whitman et al. 2004). Each “population” oflions contains a maximum of 10 prides consisting of ≤ 9females/ pride and roughly equates to numbers expectedin an area approximately 1000 km2 in East Africa (Schaller1972; Rudnai 1973) We established a standardized start-ing point for all simulations by using a population at equi-librium (in the absence of hunting) that began with anarbitrary set of individuals and an arbitrary age distribu-tion. “Founding” populations reached equilibrium within20–25 years, so we ran each simulation for 30 and 40 yearswith 100 replicates.

To test for the effects of trophy hunting, we selectedtrophy males from our standardized population accordingto age (≥3 years to ≥6 years) and removed lions at ran-dom with respect to social status (resident vs. nomad) forannual quotas ranging from 0 to 20 males. Each replicatebegan with identical age structure, reproductive history,pride affiliation, and spatial distribution. We harvestedmales at random (according to our selection criteria) ev-ery 6 months, although it was not always possible to sat-isfy the quota.

We tested for the importance of environmental stochas-ticity by harvesting an annual quota of 0 to 20 males ac-cording to age from a “recovering” population versus onethat was stable at the onset of hunting. A recovering pop-ulation began with only 5 of 10 territories occupied fromthe initial standardized population.

The fleshy part of a lion nose accrues pigmentationlinearly with age and can be used to estimate age accord-ing to a “nose pigmentation index” (NPI) (Whitman etal. 2004). We used nose coloration measurements from95 individuals of known age from the Serengeti (malesand females) and Ngorongoro Crater (females) (Whit-man et al. 2004) to group individuals into 40, 50, 60,and 70% “black” categories based on the proportion ofdark pigmentation on their noses. (We excluded malesfrom Ngorongoro Crater because of bias shown in theoriginal study.) These categories corresponded with ages4.42, 5.02, 5.61, and 6.20 years old, respectively. We cal-culated the frequency of overestimating a lion’s age withthe NPI relative to its true age. Thus, for each age classwe established a probability that a lion would be shot,based on nose pigmentation to estimate age (Table 1).We then tested for the effect of accidentally harvestingan underage animal in our model according to these fre-quencies by removing 0 to 20 lions annually from a stablepopulation.



Table 1. The probability of a male lion being shot based on aspecified percentage of nose coloration according to age class.∗

Probability (%)

Age class 40 50 60 70

3 0.17 0.08 0.00 0.004 0.67 0.17 0.00 0.005 0.82 0.73 0.36 0.096 1.00 0.88 0.63 0.387 0.75 0.75 0.75 0.758 1.00 1.00 1.00 0.75

∗Observed frequency of overestimation of lion age based on nosecoloration measurements from 95 individuals of known age fromSerengeti males and females and Ngorongoro Crater females.

Results

Female population size was highly sensitive to any quotataking >2 males/year when the harvest included lionsas young as 3 years old (Fig. 1a). Irrespective of quotasize, harvesting males at least 5 years old had a negligibleeffect on population viability. Placing age restrictions onlions shot increased the total number of males harvestedafter 30 years and increased the number of 5- and 6- yearold trophies in the population by protecting young males(Fig. 1b & c).

Harvesting older males did not reduce the population’scapacity to maintain a viable breeding population evenwhen the population was initially depleted by an environ-mental perturbation, whereas shooting younger males sig-nificantly affected the outcome. Female population sizeafter 30 years of harvesting differed very little between apopulation that was initially at equilibrium and one thatwas recovering from a perturbation event (Fig. 1a & 2).

Restricting the harvest to older age classes permittedthe initially depleted populations to recover to levels com-parable to stable populations within 15–25 years. Growthin female population size was resilient to harvesting whenannual quota size was both moderate (4 males; Fig. 3)and high (8 males; Fig. 4). Although unhunted, recov-ering populations maintained a larger number of femalesthrough time in comparison with recovering hunted pop-ulations, they grew in a similar trajectory when only males≥5 or ≥6 years were targeted. Quota size was only impor-tant when immature males (≤4 years) were taken. Extinc-tion occurred at least once per 100 runs when quota sizeexceeded more than two ≥3 or ≥4 year old males eachyear; whereas extinction never occurred when huntingwas restricted to males ≥5 or ≥6 years old.

In the absence of background demographic data,hunters who tried to follow our recommendations of a6-year age minimum could rely on nose coloration to esti-mate age. They shot only males whose noses were at least60% pigmented (cf. Table 1; Whitman et al. 2004). Giventhe observed variability in the age and nose coloration

Figure 1. Effects of 30 years of lion trophy hunting asa function of hunting quota size and male age in ahypothetical population. Average outcome after 100simulation runs is shown from shooting males in fourage groups (≥ 3, ≥4, ≥5, and ≥ 6 years old): (a)number of adult females after 30 years, (b) totalnumber of males harvested, (c) total number of 5- to6-year-old “trophies” harvested (adapted fromWhitman et al. 2004).

trend in our study population, the 60% rule could lead toa few misclassifications of overestimating the target lion’sage, but there would also be a number of older animalswhose ages were underestimated (Table 1). The overalleffect of this error was negligible (Fig. 5), and there wasno real risk of overexploiting the population if the hunt-ing industry were to enforce a 60% minimum. There is



Figure 2. Effects of 30 years of trophy hunting of malelions on the number of adult females as a function ofthe hunting quota size and male age for a populationrecovering from a hypothetical environmentaldisturbance after 100 simulation runs (males shot infour age groups: ≥3, ≥4, ≥5, and ≥6 years old).

an obvious difference in the degree of pigmentation be-tween 30% and 60% (Fig. 6), and even if hunters applieda 50% rule (for 5-year-old lions), the long-term effect onpopulation size would be small. Consistent with shoot-ing males that are a minimum of 4 years of age, extinctionnever occurred when hunters only removed males with atleast 40% black noses, although the effect on populationviability would be much less desirable.

Discussion

Modeling

In testing for measurement errors in age assessments,we found that our model was robust to minor misclas-sifications in trophy age, and the results of our analy-sis suggest that populations remained most viable whenthe harvest was limited to older males. We found nomeaningful difference in population persistence betweena simulated hunted population that was initially stableand one that was recovering from a perturbation. It is

−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−→

Figure 3. Effect of environmental disturbance onfemale population numbers through time as afunction of male age in a stable versus recoveringpopulation. Female population size when huntersshoot males that are (a) ≥3, (b) ≥4, (c) ≥5, and (d)≥6 years old. Average outcomes over 100 replicates fora stable population, a recovering population, and arecovering unhunted population are shown. The stableand recovering populations describe an annualhunting quota of four males.

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well documented that environmental factors such as dis-ease (Roelke-Parker et al. 1996; Kissui & Packer 2004),food availability (Packer & Pusey 1984, 1995), and rainfall(Hanby & Bygott 1979; Packer et al. 2005a) have a con-siderable impact on the mortality of lion cubs, but whensocial stability is high, lions can be quite resilient to dis-turbance. For example, even after a catastrophic declineof about 30% in the Serengeti population as a result of acanine distemper virus epidemic in 1993–1994 (Roelke-Parker et al. 1996; Packer et al. 1999), the populationfully recovered within a few years (Packer et al. 2005b).Further back in history, Serengeti lions were heavily ex-ploited by settlers before the establishment of the nationalpark (Turner 1987). The carrying capacity of the Serengetilions in those days was far lower due to the suppressionof the wildebeest population by rinderpest (Packer et al.2005b). Yet lion numbers grew rapidly within 10 yearsof the eradication of rinderpest in the 1960s, as soon asshort-term ecological factors were favorable (Hanby et al.1995; Packer et al. 2005a).

Populations that undergo repeated catastrophic eventsin quick succession may never return to their carryingcapacity (Kissui & Packer 2004), and small, isolated pop-ulations suffer additional risks from inbreeding (e.g., Pe-terson et al. 1998), so trophy hunting is ill-advised in cer-tain circumstances. Rather than rely on the results of ourstudy, conservation managers should take care to param-eterize our model with data from their own populationswherever possible.

Conservation Implications

In observed populations, overall pride size, resident maletenure, and the size and age of male coalitions all differbetween hunted and unhunted populations (Yamazaki1996; K.W., unpublished data). Our model suggests thatlong-term harvesting can be conducted sustainably andthe quality of trophies can be enhanced by improvingtrophy selection.

Older males tend to avoid baits set by hunters and limittheir visits to short nocturnal bouts, whereas immaturemales readily scavenge and often rest near baits, poten-tially making them more vulnerable to hunters (K.W., per-sonal observation). Therefore it is important that hunters

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Figure 4. Effect of environmental disturbance onfemale population numbers through time as afunction of male age in a stable versus recoveringpopulation. Female population size when huntersshoot males that are (a) ≥3, (b) ≥4, (c) ≥5, and (d) ≥6years old. Average outcomes over 100 replicates for astable population, a recovering population, and arecovering unhunted population are shown. The stableand recovering populations describe an annual quotaof eight males.

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Figure 5. Effects of 40 years of trophy hunting of malelions on female population size as a function ofhunting quota size and male age. Average outcomesover 100 simulation runs from shooting males ≥3,≥4, ≥5, and ≥6 years old are shown. Dotted linesshow use of nose coloration as a measure of male age:≥40% black, 4 years old; ≥50% black, 5 years old; and≥60% black, 6 years old.

be able to quickly and accurately determine the age of li-ons. The color of a lion’s nose can be quickly assessed witha nominal amount of experience. Professional huntersroutinely use high-quality binoculars, making this simplerule of thumb easy to implement (G. Damm, personalcommunication). In comparison more-stringent restric-tions exist for other big game such as Stone sheep (Ovisdalli stonei) in British Columbia, where rams must be≥8 years old and hunters are required to either countgrowth rings or ensure that the tips of the horns riseabove the bridge of the nose (British of Columbia Min-istry of Water, Land & Air Protection 2005). Professionalhunters in Tanzania are currently using the nose pigmen-tation index in concert with other aging methods (Whit-man & Packer 2007) to reduce the likelihood of shootingimmature male lions (Legendary Adventures 2005).

Legalized hunting can often improve wildlife survivor-ship and population viability by mitigating other anthro-pogenic factors (see Leader-Williams & Hutton 2005 forfurther reference). Some hunting companies actively pa-trol their concessions for poachers and remove wiresnares that threaten not only lions, but vast numbers ofother wildlife. Likewise, because hunting typically takesplace in marginal and tsetse-fly-infested areas unsuitablefor other livelihoods, it provides the best economic incen-tive for protecting wildlife in those areas (Overton 1998).Photographic tourism can generate approximately twicethe revenue, but it does so at the expense of greater im-pact on the environment in the form of cars, fuel, andother infrastructure (Overton 1998; Baldus & Cauldwell2004). In Tanzania hunting distributes wealth country-wide; photographic tourism tends to limit local benefits

Figure 6. Lion nose tips typifying colorationmeasurements: (a) 4-year-old Serengeti male with 30%nose pigmented and (b) 7-year-old Serengeti femalewith 60% nose pigmentation. Measurements weretaken following methods outlined in Whitman et al.(2004).

to the northern half of the country (Overton 1998). Inaddition, hunting areas within Tanzania are generally lo-cated immediately adjacent to national parks and providea buffer zone that protects wildlife from people and peo-ple from wildlife. With the control of problem animals onthe rise, hunting’s capacity to reduce lion-human interac-tions with local communities should not be underrated.One of the biggest issues to be addressed is ensuring thatfinancial benefits from hunting filter down to the affectedcommunities (Leader-Williams & Hutton 2005; Walpole &Thouless 2005).

Control of problem animals, antagonistic killing, poach-ing, and loss of habitat are more serious threats to lionconservation than legalized hunting. Control of problemanimals represents the single greatest factor responsiblefor lion decline outside protected areas today. Recentlyin Kenya, for example, lion numbers in Nairobi NationalPark have declined from approximately 35 lions to 9 since



1998 due to Maasai spearing 27 out of 40 lions that strayedoutside the park (Njumbi 2003).

Tourist hunting has enormous potential for minimizingthe costs of living with problem animals through eco-nomic compensation of local communities living nearhunting areas (Conover 2002). Zimbabwe’s community-owned CAMPFIRE (Communal Areas Management Pro-gramme for Indigenous Resources) contributes 50% ofeach license fee for hunting an elephant to the communityas compensation for elephant damage and as an incentiveto reduce illegal hunting (Maveneke 1996 [from Lewis &Jackson 2005]). Although no compensation scheme setup to specifically address lion-human conflict outside ahunting area currently exists, a program that compen-sated Maasai outside Nairobi National Park demonstratesthe conservation potential of such schemes. Friends ofNairobi National Park were successful in halting Maa-sai killing of lions in response to livestock depredationin 2001 by compensating local herdsmen KsH$15000(US$200) for each cow or donkey killed by a lion andKsH$2500 (US$33) for each goat (Njumbi 2003). In 1year KSH$417,500 (US$5490) was paid to the Kitengelacommunity (Njumbi 2003). Unfortunately the programwas short-lived due to lack of funds, and Maasai havesince killed at least 10 lions since the program endedin 2002 (Njumbi 2003). Because wealthy foreign touristshave demonstrated a willingness to pay for the privilege tohunt lions, compensating individuals who suffer from lionattacks or livestock depredation by establishing a fund fi-nanced by hunters through a reasonable compensationfee for each lion shot as a trophy might greatly enhancea community’s tolerance for living near lions.

If trophy hunting is to serve as a conservation toolfor lion populations outside protected areas, the industryneeds to adopt an age minimum to ensure a sustainableofftake and to address the needs of the people most likelyto be affected by living in close proximity to lions. Theresults from our model demonstrate that lion populationsare resilient to sport hunting of mature males and that en-vironmental stochasticity does not affect the predictionsof the model. An age-restricted offtake provides an easy-to-implement alternative to quotas despite some inherenterror in its application.

Acknowledgments

We thank the government of Tanzania for permis-sion to conduct research. K.L.W. appreciates supportfrom Wildlife Conservation Society, Big Game SpecialProjects Foundation of Minnesota, John D. & Cather-ine T. MacArthur Foundation, Graduate School of theUniversity of Minnesota, Dayton-Wilkie Foundation, andGlobal Wildlife Trust; C.P. acknowledges support by theMcKnight Foundation and National Science Foundation

Long-term Research in Environmental Biology and AnimalBehavior programs. We are grateful to G. Damm for con-tributing a hunter’s perspective to our work. We thank T.Gelatt, S. Thirgood, L. Frank, P. Lindsey, and an anonymousreviewer for their valuable comments on the manuscript.This material is based upon work supported by the Na-tional Science Foundation under Grant No. 0343960.

Literature Cited

Baldus, R. D. 2004. Lion conservation in Tanzania leads to serioushuman–lion conflicts with a case study of a man-eating lion killing35 people. Tanzania wildlife discussion paper no. 41. DeutscheGesellschaft fur Tecnische Zusammenarbeit (GTZ), Dar-es-Salaam,Tanzania.

Baldus, R. D., and A. E. Cauldwell. 2004. Tourist hunting and its role indevelopment of wildlife management areas in Tanzania. DeutscheGesellschaft fur Tecnische Zusammenarbeit (GTZ), Dar-es-Salaam,Tanzania.

Bauer, H., and S. Van Der Merwe. 2004. Inventory of free-ranging lionsPanthera leo in Africa. Oryx 38: 26–31.

British Columbia Ministry of Water, Land and Air Protection. 2005. Hunt-ing and trapping synopsis 2005–2006. Monday Tourism Publications,Victoria, British Columbia. Available from http://bchuntingregs.com(accessed July 2005).

Broomhead, N. G. 1997a. Procedures used by the Tourist Hunting Of-fices of the Wildlife Department. Report 1. Wildlife Division, Ministryof Natural Resources and Tourism, Dar es Salaam, Tanzania.

Broomhead, N. G. 1997b. Income arising from game hunting by touristsyear ended 30 June 1996. Report 2. Wildlife Division, Ministry ofNatural Resources and Tourism, Dar es Salaam, Tanzania.

Caro, T. M., and S. M. Durant. 1995. The importance of behavioral ecol-ogy for conservation biology: examples from Serengeti carnivores.Pages 451–472 in A. R. E. Sinclair and P. Arcese, editors. Serengeti II:dynamics, management, and conservation of an ecosystem. Univer-sity of Chicago Press, Chicago.

Chardonnet, P. 2002. Conservation of the African Lion: Contributionto a status survey. International Foundation for the Conservation ofWildlife, Paris, and Conservation Force, Metairie, Louisiana.

Child, G., and B. Child. 1990. An historical perspective of sustainablewildlife utilization. Paper prepared for workshop no. 7. 18th IUCNGeneral Assembly. World Conservation Union, Gland, Switzerland.

Conover, M. 2002. Resolving human-wildlife conflicts: the science ofwildlife management. CRC Press, Boca Raton, Florida.

Creel, S., and N. M. Creel. 1997. Lion density and population structure inthe Selous Game Reserve: evaluation of hunting quotas and offtake.African Journal of Ecology 35:83–93.

Eltringham, S. K. 1994. Can wildlife pay its way? Oryx 28:163–168.Frank, L. G. 1998. Living with lions: carnivore conservation and live-

stock in Laikipia District, Kenya. U.S. Agency for International Devel-opment contract number 623–0247-C-00–3002-00. Mpala ResearchCentre, Nanyuki, Kenya.

Frank, L. G., and R. Woodroffe. 2001. Behavior of carnivores in exploitedand controlled populations. Pages 419–442 in J. L. Gittleman, S. M.Funk, D. W. Macdonald, and R. K. Wayne, editors. Carnivore conser-vation. Cambridge University Press, Cambridge, United Kingdom.

Grimm, V., N. Dorndorf, F. Frey-Roos, C. Wissel, T. Wyszomirski, and W.Arnold. 2003. Modelling the role of social behavior in the persistenceof the alpine marmot Marmota marmota. Oikos 102:124–136.

Hanby, J. P., and J. D. Bygott. 1979. Population changes in lions and otherpredators. Pages 249–62 in A. R. E. Sinclair and M. Norton-Griffiths,editors. Serengeti: dynamics of an ecosystem. University of ChicagoPress, Chicago.

Hanby, J. P., J. D. Bygott, and C. Packer. 1995. Ecology, demography andbehavior of lions in two contrasting habitats: Ngorongoro Crater andthe Serengeti Plains. Pages 315–331 in A. R. E. Sinclair and P. Arcese,



editors. Serengeti II: dynamics, management, and conservation of anecosystem. University of Chicago Press, Chicago.

Harcourt, A. H., S. A. Parks, and R. Woodroffe. 2001. Human density asan influence on species/area relationships: double jeopardy for smallAfrican reserves? Biodiversity and Conservation 110:1011–1026.

Herremans, M., and D. Herremans-Tonnoeyr. 2000. Land use and theconservation status of raptors in Botswana. Biological Conservation94: 31–41.

Kiss, A. 1990. Living with wildlife: wildlife resource management withlocal participation in Africa. Technical paper 130. World Bank, Wash-ington, D.C.

Kissui, B. M., and C. Packer. 2004. Top-down population regulation ofa top predator: lions in the Ngorongoro Crater. Proceedings RoyalSociety of London, Series B DOI:10.1098/rspb.2004.2797.

Kock, R. A. 1995. Wildlife utilization: use it or lose it—a Kenyan per-spective. Biodiversity and Conservation 4:241–256.

Lavigne, D. M., C. J. Callaghan, and R. J. Smith. 1996. Sustainable uti-lization: the lessons of history. Pages 250–265 in V. J. Taylor and N.Dunstone, editors. The exploitation of mammal populations. Chap-man & Hall, London.

Leader-Williams, N., J. A. Kayera, and G. L. Overton. 1996. Tourist hunt-ing in Tanzania. World Conservation Union, Gland, Switzerland.

Leader-Williams, N., and J. M. Hutton. 2005. Does extractive use provideopportunities to offset conflicts between people and wildlife? Pages140–161 in R. Woodroffe, S. Thirgood, and A. Rabinowitz, editors.People and wildlife: conflict or coexistence? Cambridge UniversityPress, Cambridge, United Kingdom.

Legendary Adventures. 2005. Choosing the right lion. LegendaryAdventures, Houston, Texas. Available from http://www.legendaryadventures.com/LAI-hunting/files/lionarticle.pdf (access-ed July 2005).

Lewis, D. M., and P. Alpert. 1997. Trophy hunting and wildlife conser-vation in Zambia. Conservation Biology 11:59–68.

Lewis, D., and J. Jackson. 2005. Safari hunting and conservation on com-munal land in southern Africa. Pages 239–251 in R. Woodroffe, S.Thirgood, and A. Rabinowitz, editors. People and wildlife: conflict orcoexistence? Cambridge University Press, Cambridge, United King-dom.

Loveridge, A. J., T. Lynam, and D. W. Macdonald. 2001. Lion conserva-tion research, workshop 1: survey techniques. Wildlife ConservationResearch Unit, University of Oxford, Oxford, United Kingdom.

Luck, G. W., T. H. Ricketts, G. C. Daily, and M. Imhoff. 2004. Alleviatingspatial conflict between people and biodiversity. Proceedings ofthe National Academy of Sciences of the United States of America101:182–186.

MacKenzie, J. M. 1988. The empire of nature: hunting, conservation,and British imperialism. Manchester University Press, Manchester,United Kingdom.

Maveneke, T. 1996. The elephant’s importance to CBCD: the CAMPFIREexample. Pages 31–33 in Rural development and conservation inAfrica. African Resources Trust, Harare, Zimbabwe.

McGreal, C. 2001. Lions face new threat: they’re rich, American andthey’ve got guns. The Guardian Unlimited, 27 April. Available fromhttp://www.guardian.co.uk/international/story/03604479311,00.html (accessed October 2006).

Nowell, K., and P. Jackson, editors. 1996. Wild cats, status surveyand conservation action plan. World Conservation Union, Gland,Switzerland.

Njumbi, S. 2003. The surviving lions need not perish. Daily Na-tion (Nairobi, Kenya). Available from http://63.110.5.89/news/DailyNation/27062003/Comment/Comment270620033.html (accessedJuly 2005).

Ogada, M. O., R. Woodroffe, N. O. Oguge, and L. G. Frank. 2003. Limitingdepredation by African carnivores: the role of livestock husbandry.Conservation Biology 17:1521–1530.

Ogutu, J. O., N. Bhola, and R. Reid. 2005. The effects of pastoralism and

protection on the density and distribution of carnivores and theirprey in the Mara ecosystem of Kenya. Journal of Zoology, London265:281–293.

Overton, G. 1998. The good, the bad, and the ugly. Swara 20 & 21:22–24.

Packer, C. 2000. Infanticide is no fallacy. American Anthropologist102:829–830

Packer, C., S. Altizer, M. Appel, E. Brown, J. Martenson, S. J. O’Brien,M. Roelke-Parker, R. Hofmann-Lehmann, and H. Lutz. 1999. Virusesof the Serengeti: patterns of infection and mortality in African lions.Journal of Animal Ecology 68:1161–1178.

Packer, C., L. Herbst, A. E. Pusey, J. D. Bygott, S. J. Cairns, J. P. Hanby, andM. Borgerhoff-Mulder. 1988. Reproductive success of lions. Pages363–383 in T. H. Clutton-Brock, editor. Reproductive Success. Uni-versity of Chicago Press, Chicago.

Packer, C., D. Ikanda, B. Kissui, and H. Kushnir. 2005a. Lion attacks onhumans in Tanzania. Nature 436:927–928.

Packer, C., R. Hilborn, A. Mosser, B. Kissui, M. Borner, G. Hopcraft,J. Wilmshurst, S. Mduma, and A. R. E. Sinclair. 2005b. Ecologicalchange, group territoriality and population dynamics in Serengetilions. Science 307:390–393.

Packer, C., and A. E. Pusey. 1983a. Adaptations of female lions to in-fanticide by incoming males. The American Naturalist 121:716–728.

Packer, C., and A. E. Pusey. 1983b. Male takeovers and female reproduc-tive parameters: a simulation of oestrus synchrony in lions (Pantheraleo). Animal Behaviour 31:334–340.

Packer, C., and A. E. Pusey. 1984. Infanticide in carnivores. Pages 31–42in G. Hausfater and S. B. Hardy, editors. Infanticide: comparative andevolutionary perspectives. Aldine, New York.

Packer, C., and A. E. Pusey. 1995. The Lack clutch in a communalbreeder: lion litter size is a mixed evolutionarily stable strategy. TheAmerican Naturalist 145:833–841.

Packer, C., A. E. Pusey, and L. Eberly. 2001. Egalitarianism in femaleAfrican lions. Science 293:690–693.

Packer, C., M. Tatar and D. A. Collins. 1998. Reproductive cessation infemale mammals. Nature 392:807–11.

Peterson, R. O., N. J. Thomas, J. M. Thurber, J. A. Vucetich, and T. A.Waite. 1998. Population limitation and the wolves of Isle Royale.Journal of Mammalogy 79:828–841.

Planning and Assessment for Wildlife Management (PAWM). 1995. Pages63–76 in N. Leader-Williams, J. A. Kayera, and G. L. Overton, editors.Tourist hunting in Tanzania. Tanzania. Ministry of Natural Resourcesand Tourism, Dar es Salaam, Tanzania

Quadling, H. S., and A. M. Starfield. 2002. Exploiting object-orientedprogramming structures in the quest for an individual-based lionpopulation model with an attractive user interface. South AfricanJournal of Science 98:449–454.

Roelke-Parker, M. E., et al. 1996. A canine distemper virus epidemic inSerengeti lions (Panthera leo). Nature 379:441–445

Rudnai, J. 1973. Reproductive biology of lions (Panthera leo massaicaNeumann) in Nairobi National Park. East African Wilidlife Journal11:241–253.

Safari Club International (SCI). 1997. African lion. Pages 12–27 in TheSCI record book of trophy animals. XI edition, Volume 1, Africa. SCI,Tuscon, Arizona.

Schaller, G. B. 1972. The Serengeti lion. The University of Chicago Press,Chicago.

Severrre, E. L. M. 1995. Setting quotas for tourist hunting in Tanzania.Pages 52–53 in N. Leader-Williams, J. A. Kayera, and G. L. Overton,editors. Tourist hunting in Tanzania. Ministry of Natural Resourcesand Tourism, Dar es Salaam, Tanzania.

Starfield, A. M., P. R. Furniss, and G. L. Smuts. 1981. A model of lionpopulation dynamics as a function of social behavior. Pages 121–134 in C. W. Fowler, editor. Dynamics of large mammal populations.Wiley-Interscience, New York.



Treves, A., and K. U. Karanth. 2003. Human-carnivore conflict and per-spectives on carnivore management worldwide. Conservation Biol-ogy 17:1491–1499.

Turner, M. 1987. My Serengeti years. W.W. Norton, New YorkVucetich, J. A., R. O. Peterson, and T. A. Waite. 1997. Effects of social

structure and prey dynamics on extinction risk in gray wolves. Con-servation Biology 11:957–965.

Walpole, M. J., and C. R. Thouless. 2005. Increasing the value of wildlifethrough nonconsumptive use: deconstructing the myths of eco-tourism and community based tourism in the tropics. Pages 122–139in R. Woodroffe, S. Thirgood, and A. Rabinowitz, editors. People andwildlife: conflict or coexistence? Cambridge University Press, Cam-bridge, United Kingdom.

Whitman, K. L. 2002. Safari Hunting of Lions: A review of policies,practices and industry concerns. Pages 111–124 in H. O. De Waal,editor. Proceedings of the 2nd meeting of the African Lion Work-ing Group, 2002. World Conservation Union, African Lion WorkingGroup, Brandhof, Republic of South Africa.

Whitman, K. L., and C. Packer. 1997. The effect of sport hunting onthe population dynamics of the African lion. Pages 177–183 in J. vanHeerden, editor. Proceedings of a symposium on lions and leopards

as game ranch animals. South African Veterinary Wildlife Group,Faculty of Veterinary Science, Onderstepoort, Republic of SouthAfrica.

Whitman, K. L., and C. Packer. 2007. A hunter’s guide to aging lions ineastern and southern Africa, Safari Press, Longbeach, California.

Whitman, K., A. M. Starfield, H. S. Quadling, and C. Packer. 2004.Sustainable trophy hunting of African lions. Nature 428:175–178.

Wildlife Division. 2003. Reference manual for implementing guide-lines for the designation and management of wildlife management(WMAs) in Tanzania. Ministry of Natural Resources and Tourism,Dar es Salaam, Tanzania.

Woodroffe, R. 2001. Strategies for carnivore conservation: lessons fromcontemporary extinctions. Pages 61–92 in J. L. Gittleman, S. M.Frank, D. MacDonald, and R. K. Wayne, editors. Carnivore conser-vation. Cambridge University Press, Cambridge, United Kingdom.

Woodroffe, R., and J. R. Ginsberg. 1998. Edge effects and the ex-tinction of populations inside protected areas. Science 280:2126–2128.

Yamazaki, K. 1996. Social variation of lions in a male-depopulated areain Zambia. Journal of Wildlife Management 60:490–497.


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