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Sustainable trophy hunting of Africa lions

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Karyl Whitman at University of Minnesota
Karyl Whitman
Anthony M Starfield
Anthony M Starfield
Anthony M Starfield
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Henley S Quadling
Henley S Quadling
Henley S Quadling
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Craig Packer at University of Minnesota
Craig Packer
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Abstract and Figures

In most species, sport hunting of male trophy animals can only reduce overall population size when the rate of removal of males is so high that females can no longer be impregnated. However, where males provide extensive paternal care, the removal of even a few individuals could harm the population as a whole. In species such as lions, excessive trophy hunting could theoretically cause male replacements (and associated infanticide) to become sufficiently common to prevent cubs reaching adulthood. Here we simulate the population consequences of lion trophy hunting using a spatially explicit, individual-based, stochastic model parameterized with 40 years of demographic data from northern Tanzania. Although our simulations confirm that infanticide increases the risk of population extinction, trophy hunting could be sustained simply by hunting males above a minimum age threshold, and this strategy maximizes both the quantity and the quality of the long-term kill. We present a simple non-invasive technique for estimating lion age in populations lacking long-term records, and suggest that quotas would be unnecessary in any male-only trophy species where age determination could be reliably implemented.
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Sustainable trophy hunting
of African lions
Q1
Karyl Whitman, Anthony M. Starfield, Henley S. Quadling & Craig Packer
Department of Ecology, Evolution and Behavior, University of Minnesota,
1987 Upper Buford Circle, Saint Paul, Minnesota 55108, USA
.............................................................................................................................................................................
In most species, sport hunting of male trophy animals can only
reduce overall population size when the rate of removal of males
is so high that females can no longer be impregnated
1
. However,
where males provide extensive paternal care, the removal of even
a few individuals could harm the population as a whole
2,3
.In
species such as lions, excessive trophy hunting could theoretically
cause male replacements (and associated infanticide
4,5
)to
become sufficiently common to prevent cubs reaching adulthood.
Here we simulate the population consequences of lion trophy
hunting using a spatially explicit, individual-based, stochastic
model parameterized with 40 years of demographic data from
northern Tanzania. Although our simulations confirm that
infanticide increases the risk of population extinction, trophy
hunting could be sustained simply by hunting males above a
minimum age threshold, and this strategy maximizes both the
quantity and the quality of the long-term kill. We present a
simple non-invasive technique for estimating lion age in popu-
lations lacking long-term records, and suggest that quotas would
be unnecessary in any male-only trophy species where age
determination could be reliably implemented.
Male lions reach sexual maturity at about 2.5 yr of age and live to
a maximum of about 15 yr in nature
6
. The lion’s mane reaches full
size at about 4 yr (ref. 7), and peak reproductive success is attained
by about 8 yr (ref. 8). African lions live in stable social groups
(‘prides’) containing an average of six breeding females and a
coalition of 2–3 adult males. The resident coalition sires all cubs
born during their tenure
9
, but most coalitions only remain resident
for about 2 yr on average
—
long enough to rear a single cohort of
young to independence
10
. Rather than wait for mothers with
dependent offspring to rear their current brood, incoming males
typically kill all cubs #9 months of age and evict older subadults
when they first take over a pride
4,5
. Trophy hunting is expected to
increase the rate of male takeovers, as larger coalitions dominate
smaller ones
11
and the loss of even one male from a resident
coalition renders it more vulnerable to being ousted
12
.
We developed a comprehensive simulation model that tracks the
fate of each individual in a population
13
(see Methods), and we
present results based on ‘populations’ comprising a maximum of
ten prides of #9 females per pride. Outcomes of hunting should be
most sensitive to factors that limit population size: the maximum
number of prides in the population, maximum pride size, and the
incidence of infanticide. We therefore ran simulations of popu-
lations containing a maximum of five prides with #10 females and
ten prides with #7 females, and our conclusions were unchanged.
The impact of infanticide is emphasized below (see Fig. 1). At each
six-month time step, animals survive and breed according to
probabilities observed in the long-term lion studies in the Serengeti
National Park and in Ngorongoro Crater
14,15
. Demographic param-
eters depend on the age, sex and social status of individual lions.
Probability of female recruitment depends on the number of adult
females in the pride, whereas probability of male takeovers depends
onthesizeandageofresidentcoalitionsversuschallenging
nomadic coalitions. An emerging property of these interactions is
a density-dependence that leads to a quasi-equilibrium where the
total population size fluctuates slightly (with demographic stochas-
ticity) around a well-defined average. Preliminary trials started the
populations with an arbitrary set of individuals and an arbitrary age
distribution, and proceeded (without trophy hunting) until the
population reached a stable size and age-structure that served as the
standardized starting point for all simulations.
Trophy-hunting strategies were varied in two ways. First, the
minimum age of eligible males ranged from $3yrto$6 yr. Second,
quotas could range from 0 to 20 males per year. Individual males
were removed according to the age minimum, but at random with
respect to pride or nomadic status. Figure 1 illustrates the effects
of these strategies after 30 yr (as start-up populations required
20–25 yr to equilibrate). Figure 1a and b shows that if offtake
included males as young as three years of age, the female population
would invariably collapse if quotas were too high. But as the
minimum age of trophy males was raised, the chances of population
persistence increased markedly
—
to the point where removing males
$6 yr in age had no substantial effect regardless of quota size. Note
Figure 1 Effects of trophy hunting as a function of quota size and male age. Average
outcome after 100 runs is shown from shooting males of the following ages: $3 yr old
(red), $4 yr (orange), $5 yr (blue), $6 yr (green). a, Number of adult females after 30 yr
in hypothetical populations where males are non-infanticidal. b, Number of females in
infanticidal populations; note that infanticidal populations are smaller and more vulnerable
to trophy hunting. c, Total number of males harvested over 30 yr in infanticidal
populations. d, Total number of 5–6-yr-old ‘trophies’ harvested in infanticidal
populations.
Figure 2 Female population size through time as a function of quota size and male age in
infanticidal populations. Red indicates average outcome over 100 runs from annual
quota of 10 males, orange from quota of 6 males, blue from quota of 4, and green from
quota of 2. a–d, Female population size when hunters shoot males that are $3 yr old (a),
$4yr (b), $5yr(c) and $6yr(d).
letters to nature
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that the sensitivity to over-hunting is exacerbated by infanticide: if
we eliminate infanticide from the model, the resultant populations
are always larger regardless of hunting strategy (Fig. 1a)
—
but
removing too many young males will still drive the population to
extinction because females are eventually unable to mate. Figure 2
shows the average size of the female population through time as a
function of male age and quota size. Shooting too many young
males leads to an inevitable decline in population size, whereas
quota size is irrelevant when hunting is restricted to older males.
Running the simulations for 50 yr in infanticidal populations,
quotas of more than two $3- or $4-yr-old males per year produced
at least one case of extinction per 100 runs, whereas there were no
extinctions when hunting was restricted to $5- or $6-yr-olds.
By only removing $5- or $6-yr-old males, younger males have
the opportunity to remain resident long enough to rear a cohort of
young. By removing males in a manner that sustains population
growth, the population can yield more males in the long run. Figure
1c and d shows that the cumulative number of males harvested over
30yrisalsosensitivetomaleageandquota,but,again,the
detrimental impact of trophy hunting is largely avoided by main-
taining a minimum age of 5–6 yr, and the total number of high-
quality ‘trophies’ (large-maned males of 5–6 yr) taken at random
from these populations is also highest. Hunting fees are highest in
reserves with greater opportunities to shoot trophy animals, so it is
noteworthy that the most impressive males are so ‘expendable’ to
the population. Figure 3 shows the expected annual harvest of
‘trophy males’ through time. By restricting offtake to $5- or $6-yr-
old males, hunters harvest a greater cumulative number of trophy
males and are likely to gain a steadier offtake each year.
Hunters often estimate male age on the basis of mane size or
colouration, but these phenotypes are only loosely correlated with
age and vary greatly across the geographic range of the lion
7
. The
most reliable index in the Serengeti/Ngorongoro lions is the extent
of dark pigmentation in the tip of the nose, which becomes
increasingly freckled with age (Fig. 4). Individual variation in
nose colouration is sufficiently low that age can be estimated up
to 8–9 yr (Table 1). The noses of 5-yr-old males are 50% black, so a
simple rule of thumb would be to restrict all trophy hunting to
males with noses that are more than half black. However, the noses
of Ngorongoro males darkened more slowly than Ngorongoro
females and Serengeti males/females (Fig. 4), thus site-specific
data may be necessary to provide accurate age estimates. However,
in areas with slower rates of nose darkening, the 50% rule would
safely restrict hunting to $8-yr-old males.
Detailed predictions of these simulations should be interpreted
with caution, because they rely on demographic patterns in two
adjacent populations in northern Tanzania and may not apply to
every situation. Nevertheless, our results do point to possible
conflicts between conservation and consumption. Figures 1b and
2 suggest that lion populations will be larger if trophy hunting is
restricted to males $6 yr, but this strategy entails an opportunity
cost: long-term harvests are highest from hunting males with ages
$5 yr (Fig. 1c and d, Fig. 3). Our analysis also treats the lion
population as a ‘closed system’, sustained solely by birth rates of the
resident females, which exemplifies populations most at risk from
overexploitation. ‘Open’ systems involve game reserves immediately
adjacent to national parks where excess males and females can freely
disperse from protected areas into low density hunting areas. Our
analysis also assumes that trophies are removed at random accord-
ing to residence status. If hunters followed a more sophisticated
approach by selectively targeting nomadic males or resident males
whose cubs have recently reached independence, trophy hunting
Figure 3 Annual offtake of 5–6-yr-old ‘trophy’ males as a function of quota size and male
age in infanticidal populations. Red indicates average outcome of 100 runs from
annual quota of 10 males, orange from quota of 6 males, blue from quota of 4, and green
from quota of 2. Annual offtake of trophies when hunters shoot males that are $3 yr old
(a), $4yr(b), $5yr (c) and $6yr (d).
Figure 4 Age estimation for adult lions using nose colouration. a, Identification
photograph of a 3-yr-old Serengeti male. b, Excised photo of nose tip. c, GIS rendering of
nose colouration. d, Age-change of nose colouration for males and females in two
separate populations. After controlling for age, there was no effect of sex on nose colour in
the Serengeti, but Ngorongoro males had lighter noses than Ngorongoro females
(P ¼ 0.0485) and Serengeti males (P ¼ 0.0281).
letters to nature
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could greatly reduce the incidence of infanticide, and population
sizes would approach the levels predicted by Fig. 1a.
Assuming an average pride range of 100 km
2
, our simulated
population of 10 prides would yield fewer than 3 males per
1,000 km
2
per year (Fig. 1c). Hunting quotas in 34 reserves in
Tanzania in 1995 were set at an average of 3.8 males per 1,000 km
2
(median, 2.8; range, 0.5–13.4). Although the expectations from
these concessions were generally set at an appropriate order of
magnitude, quotas have increased in many Tanzanian reserves over
the past five years, and quotas are even higher in parts of Africa
where lion population densities are considerably lower. Therefore,
realistic lion harvests for most areas may not generate sufficient
revenue to be economically viable in the long term unless conces-
sions establish an auction system
16
or sell hunting ‘opportunities’
(which may or may not succeed in killing a lion) rather than attempt
to base their income exclusively on successful hunts.
Our model shows clearly that age is a critical variable enabling the
persistence of trophy species with extensive paternal care. As long as
hunting is restricted to a safe minimum age (and the rule is honestly
enforced
17
), there is no risk of setting excessive quotas even in areas
where it is impossible to estimate the overall population size
18
.
Lions’ noses continue to darken until they are at least 9 yr old, so
rough estimates of male age can easily be made (Table 1). Thus
despite the complexity of lion social structure and the complex
consequences of male removal, populations can be sustained by
following a simple harvest rule, combined with a simple technique
for age-assessment.
Although our model was designed to examine the impact of
trophy hunting in only one species, our findings have broad
significance. First, highly valued ‘trophy’ animals are individuals
with unusually well-developed secondary sexual characteristics,
such as large antlers, horns, tusks or mane. Although these traits
generally grow with age, high-quality individuals may show preco-
cious physical development and thus be shot before they are able to
breed
—
with negative evolutionary effects on the population as a
whole
19
. Thus it is particularly important to assess age indepen-
dently from the ‘trophy’ phenotype, and to set age thresholds high
enough to ensure successful breeding by the best males. Second, the
hunting industry has always been based on some sort of quota
system, even though quotas are generally viewed as arbitrary and
difficult to enforce
16,20,21
. Our analysis suggests that quotas could
eventually become irrelevant to the conservation of lions and any
other trophy species (whether infanticidal or not) where hunting is
restricted to males. With basic information on breeding biology and
social behaviour (such as infanticide and other quirks of male
behaviour
22
), an age-threshold criterion could be calculated that
would minimize the adverse effects from killing all of the eligible
males each year. By excluding the younger adult males from the
annual kill, females would always be impregnated and vulnerable
offspring would generally be protected by their fathers. A
Methods
Simulation model
In the Windows-driven Cþþ model
12
, female lions and their dependent offspring are
organized into ‘prides’ that defend spatially arranged and interconnected territories. The
model ignores environmental stochasticity, so the maximum number of territories and
maximum pride size is held constant for a given set of simulations. The model
distinguishes between sex and age class (cubs ,6 months, cubs 6–12 months, cubs 12–24
months, subadult males and females, adult males and females) and tracks individuals by
social and reproductive status. Only 3–13-yr-old females produce cubs; females are not
able to breed again until they lose their entire litter or their surviving offspring reach 2 yr of
age. Males are classified as either subadult, nomadic or resident; lone males may join up
with other lone males or groups of two. Nomadic and subadult males move freely between
and within pride territories a specified number of times per time step, but do not breed
with females. Residents may be affiliated with up to 3 prides at once. Competition for pride
residence is determined by using a competition matrix
23
that weights overall competitive
strength according to male age and coalition size. Cubs are killed with an age-specific
probability when new males first enter a pride.
At each time step, the model simulates cub production using a random number for
each eligible female that draws her litter size from a distribution, determines individual
survival (assigned by random number according to the observed survival rate for animals
of that age, sex and social status
—
see Supplementary Information), updates ages for
survivors, organizes 2-yr-old males in each pride into subadult male groups, promotes
3-yr-old males into nomadic groups, and determines the fate of subadult females.
Recruitment of females into their natal pride depends on the number of adult females
already in the pride and the specified upper limit for that pride (which can be temporarily
exceeded by no more than two females). If the subadult females cannot be accommodated
in their natal pride, they are allowed to search for empty territories, but they die if they
cannot find any vacancies. At ‘equilibrium’, the simulated populations closely matched real
populations in terms of the male:female:cub ratio, the average age of resident males, and
the size range of subadult cohorts. To test the effects of trophy hunting, each simulation
ran for 30 or 50 yr with 100 replicates. The initial age structure, reproductive history, pride
affiliation, and distribution were identical for each replicate. Harvesting occurred at
random (within the rules) every 6 months, although it was not always possible to meet the
quota.
Nose assessments
Close-up colour photographs (n ¼ 189) were taken of 105 known-aged lions, including 73
females and 32 males from the Serengeti National Park and Ngorongoro Crater, Tanzania,
between 1999 and 2002. Each photograph was first digitized at high resolution into a.tif
file, and the fleshy part of the nose (‘nose tip’) from each image was excised using Adobe
Photoshop 4.01 LE. We then used the Spatial Analyst extension of ESRI Arcview 3.2 to
rasterize each cut-out nose tip and assign each newly created ‘grid’ a range of colour values.
By limiting the colour values to either ‘black’ or ‘not black’, the nasal pigmentation pattern
was ‘mapped’ and quantified for the percentage of readable pixels that contained ‘black’.
We used linear multiple regression to assess the effect of age, sex, habitat and population
on pigmentation. In cases where multiple photographs were available for the same
individual, the mean pigmentation score was regressed against mean age.
Received 25 November 2003; accepted 4 February 2004; doi:10.1038/nature02395.
Published online 22 February 2004.
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Table 1 Statistical relationship between nose blackness and age
Proportion
black
Estimated age
in years (s.e.)
95% p.i 75% p.i 50% p.i
.............................................................................................................................................................................
0.10 2.66 (1.24) 0.17–5.15 1.21–4.10 1.81–3.50
0.20 3.25 (1.24) 0.77–5.72 1.81–4.69 2.41–4.09
0.30 3.84 (1.23) 1.37–6.30 2.40–5.27 3.00–4.68
0.40 4.42 (1.23) 1.97–6.89 3.00–5.86 3.59–5.26
0.50 5.02 (1.23) 2.56–7.48 3.59–6.45 4.18–5.85
0.60 5.61 (1.23) 3.14–8.07 4.18–7.04 4.77–6.44
0.70 6.20 (1.23) 3.73–8.66 4.77–7.63 5.36–7.04
0.80 6.79 (1.24) 4.32–9.26 5.35–8.23 5.95–7.63
0.90 7.38 (1.24) 4.90–9.87 5.94–8.82 6.54–8.22
1.00 7.97 (1.25) 5.58–10.47 6.52–9.42 7.12–8.82
.............................................................................................................................................................................
s.e., standard error; p.i., predicted interval. Predicted values are based upon the least-squares
regression of a truncated data set for 63 known-aged females in the Serengeti and Ngorongoro
aged #10 yr (y ¼ 2.0667 þ 5.9037arcsin(x); r
2
¼ 0.75, P , 0.0001). Predicted intervals at 95%,
75% and 50% are included for upper and lower bounds.
letters to nature
NATURE | doi:10.1038/nature02395 | www.nature.com/nature 3
19. Coltman, D. W. et al. Undesirable evolutionary consequences of trophy hunting. Nature 426, 655–658
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(ed. Fowler, C. W.) 121–134 (Wiley, New York, 1981).
Supplementary Information accompanies the paper on www.nature.com/nature.
Acknowledgements We thank the government of Tanzania for permission; K.W. was supported
by the Wildlife Conservation Society, Big Game Special Projects Foundation, John D. & Catherine
T. MacArthur Foundation, Graduate School of the University of Minnesota, Dayton-Wilkie
Foundation, and Global Wildlife Trust; C.P. was supported by the McKnight Foundation and NSF
LTREB and Animal Behavior programmes. We thank T. Gelatt, P. West, G. Hopcraft, M. Craft,
B. Kissui, L. Frank, S. Mduma, T. Ramme, W. Testa, T. Coulson and N. Leader-Williams for
advice, assistance and discussion.
Competing interests statement The authors declare that they have no competing financial
interests.
Correspondence and requests for materials should be addressed to C.P. (packer@cbs.umn.edu).
letters to nature
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Author Queries
JOB NUMBER: 2395
JOURNAL: Nature
Table count =1 Figure count =4
Q1 In Acknowledgements, please clarify ‘permission’; per-
mission for what? Please note that we have left ‘kill’ rather
than ‘harvest’ in the first paragraph, as this will help the
general reader. Please check that the display items are as
follows (doi:10.1038/nature02395): Figures 1–4 (all col-
our); Tables 1; Boxes none. Please check all figures (and
tables if any) very carefully as they have been re-labelled,
re-sized and adjusted to Nature’s style.Article classifi-
cation: broad area …1, 9, 12; subclassification
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... Nomadic males play a key role in shaping lion demography (Borrego et al., 2018;Whitman et al., 2004). Male coalitions compete for access to prides; coalitions successfully taking over a pride from a rival coalition gain reproductive benefits by killing the ousted coalition's cubs (infanticide; Packer & Pusey, 1983a, 1983b) and subsequently mating with its females. ...
... Lions were identified by eye based on photographs of features such as scars and individual-specific whisker spots recorded at the first sighting (Packer & Pusey, 1993;Pennycuick & Rudnai, 1970). The age of individuals not observed as cubs was determined from nose coloration, coat condition and tooth wear (Whitman et al., 2004). ...
... Number of adult females in the pride Young-subadult survival Takeovers can be prevented by females protecting their offspring, thus reducing the probability of a successful takeover in groups of females compared to singletons (Grinnell & McComb, 1996), and consequently the mortality of young individuals (Packer et al., 1990). However, small and large prides can attract nomadic coalitions more, leading to a higher takeover rate in these prides and thereby a higher mortality of young through infanticide or forced dispersal (Elliot et al., 2014;Packer & Pusey, 1987;Pusey & Packer, 1994), with potentially severe consequences at the population level (Whitman et al., 2004) Moreover, the survival of adult females can be affected by the size of the pride: Females in small prides have lower survival rates, probably due to encounters with infanticidal males or females of other prides competing for the territory (Packer & Pusey, 1997;Pusey & Packer, 1994). Reproduction probability Reproduction is mainly driven by takeover dynamics and interpride competition (Packer, 2023), with small prides being unable to defend their cubs against outside males or their territories against larger neighbouring prides, and large prides attracting more frequent male takeovers and suffering greater within-pride feeding competition. ...
Multifaceted density dependence: Social structure and seasonality effects on Serengeti lion demography
Article
Full-text available
Interactions between density and environmental conditions have important effects on vital rates and consequently on population dynamics and can take complex pathways in species whose demography is strongly influenced by social context, such as the African lion, Panthera leo. In populations of such species, the response of vital rates to density can vary depending on the social structure (e.g. effects of group size or composition). However, studies assessing density dependence in populations of lions and other social species have seldom considered the effects of multiple socially explicit measures of density, and—more particularly for lions—of nomadic males. Additionally, vital‐rate responses to interactions between the environment and various measures of density remain largely uninvestigated. To fill these knowledge gaps, we aimed to understand how a socially and spatially explicit consideration of density (i.e. at the local scale) and its interaction with environmental seasonality affect vital rates of lions in the Serengeti National Park, Tanzania. We used a Bayesian multistate capture–recapture model and Bayesian generalized linear mixed models to estimate lion stage‐specific survival and between‐stage transition rates, as well as reproduction probability and recruitment, while testing for season‐specific effects of density measures at the group and home‐range levels. We found evidence for several such effects. For example, resident‐male survival increased more strongly with coalition size in the dry season compared with the wet season, and adult‐female abundance affected subadult survival negatively in the wet season, but positively in the dry season. Additionally, while our models showed no effect of nomadic males on adult‐female survival, they revealed strong effects of nomads on key processes such as reproduction and takeover dynamics. Therefore, our results highlight the importance of accounting for seasonality and social context when assessing the effects of density on vital rates of Serengeti lions and of social species more generally.
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... Selective harvesting by sex is particularly relevant for species in which females and males differ in behavior, morphology, or economic value. For instance, the extraction of adult males is quite common in commercial harvesting or trophy hunting [20][21][22][23][24][25]. The removal of mature females is often prohibited or performed simultaneously with other groups. ...
... Harvesting can influence population structure and induce changes in phenotypic traits and behavior, thus indirectly impacting the population growth rate and, consequently, the dynamics and sustainable development of the population [21]. In long-lived mammals, hunting-induced selection typically affects secondary sexual traits in males, such as the antlers and horns of mule deer, elk, white-tailed deer, and bighorn sheep [63,64], as well as body mass [65]. ...
... Consequently, when an abundance of males is plentiful, a higher harvest rate can result in the emergence and amplification of quasiperiodic oscillations. With an increase in the value of the parameter u m , crossing the threshold value defined by relation (21) means that the number of mature females in the population exceeds the number of forming pairs: f > hm (Figure 8b). Simultaneously, the stability region of the nontrivial fixed point of the system (16) expands for the same values of the birth rate a. ...
Discrete-Time Model of an Exploited Population with Age and Sex Structures: Instability and the Hydra Effect
Article
Full-text available
  • Feb 2024
This study proposes a discrete-time mathematical model to investigate the impact of selective harvesting on the dynamics of a population with age and sex structures. The model assumes that the birth rate depends on the sex ratio of the population and the number of breeding pairs. The growth rate is regulated by limiting juvenile survival, where an increase in population size decreases the survival of immature individuals. We consider the following selective proportional exploitation: harvesting of juveniles and harvesting of mature males. Depending on the values of population parameters, selective harvesting can lead to the stabilization of population dynamics by dampening oscillations or the emergence and amplification of fluctuations in population size. The model reveals multistability domains in which different dynamic modes coexist, and variations in initial conditions can lead to changes in dynamic modes. Depending on the values of the population parameters, the proposed models with harvest reveal the hydra effect, indicating an increase in the equilibrium abundance of the exploited group after reproduction but before harvesting, with an increase in the harvesting rate. Selective harvesting, resulting in the hydra effect, increases the remaining population size due to reproduction and the number of harvested individuals.
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... Although lions are the most-studied species in the African large carnivore guild (Strampelli et al., 2022), empirical analyses of their demographic responses to management and conservation actions remain rare, and mostly restricted to the effects of trophy hunting Loveridge et al., 2007Loveridge et al., , 2016Mweetwa et al., 2018;Rosenblatt et al., 2014;Whitman et al., 2004). found that low prey density due to bushmeat poaching in the GKE caused lion density to be low, primarily due to poor cub recruitment (rather than poor adult survival). ...
... We identified lions by whisker-spot patterns, nose-pigmentation patterns, scarring, and tooth wear (Pennycuick & Rudnai, 1970), using a database of digital photographs. For lions whose age was unknown, age was estimated using calibrated standards for nose-pigmentation pattern, tooth wear and coloration, and facial scarring (Miller et al., 2016;Whitman et al., 2004). We validated the accuracy of age assignments with known-age individuals in this population and in another Zambian population with a longer-running study (Mweetwa et al., 2018). ...
Changes in African lion demography and population growth with increased protection in a large, prey‐depleted ecosystem
Article
Full-text available
  • Dec 2024
Large carnivores such as the lion are declining across Africa, in part because their large herbivore prey is declining. There is consensus that increased protection from prey depletion will be necessary to reverse the decline of lion populations, but few studies have tested whether increased protection is sufficient to reverse the decline, particularly in the large, open ecosystems where most lions remain. Here, we used an integrated population model to test whether lion demography and population dynamics were measurably improved by increased protection. We used data from monitoring of 358 individuals from 2013 to 2021 in the Greater Kafue Ecosystem, where prior research showed that lions were strongly limited by prey depletion, but protection increased in several well‐defined areas beginning in 2018. In some other areas, protection decreased. In areas with high protection, lion fecundity was 29% higher, and mean annual apparent survival (φ) was 8.3% higher (with a minimum difference of 6.0% for prime‐aged adult females and a maximum difference of 11.9% for sub‐adult males). These demographic benefits combined to produce likely population growth in areas with high protection (λ̂ = 1.085, 90% CI = 0.97, 1.21), despite likely population decline in areas with low protection (λ̂ = 0.970, 90% CI = 0.88, 1.07). For the ecosystem as a whole, population size remained relatively constant at a moderate density of 3.74 (±0.49 SD) to 4.13 (±0.52 SD) lions/100 km². With the growth observed in areas with high protection, the expected doubling time was 10 years. Despite this, recovery at the scale of the entire ecosystem is likely to be slow without increased protection; the current growth rate would require 50 years to double. Our results demonstrate that increased protection is likely to improve the reproduction and population growth rate of lions at a large scale within an unfenced ecosystem that has been greatly affected by poaching.
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... Panthera leo was recently assessed for The IUCN Red List of Threatened Species in 2023 [2], and is listed as Vulnerable under criteria A2abcd. Lions are hunted for sport [3,4], poached [5], used in traditional medicine [6,7], in an expensive wine also used in traditional medicine [8], or killed by farmers in retaliation for livestock attacks [9]. PCR or qPCR is considered the 'gold standard' in many scientific disciplines, including forensic DNA typing. ...
Developmental Validation of DNA Quantitation System, Extended STR Typing Multiplex, and Database Solutions for Panthera leo Genotyping
Article
Full-text available
  • Apr 2025
This study describes the development of a species determination/DNA quantification system called Pleo Qplex and an individual identification STR multiplex called Pleo STRplex using Panthera leo samples. Pleo Qplex enables us to measure the quantity of extracted nuclear and mitochondrial DNA and detect the presence of co-purified inhibitors. Pleo STRplex, consisting of seven loci, enables the determination of the DNA profile from a sample of Panthera leo based on the analysis of short tandem repeats (STRs). The Pleo STRplex provides additional loci on top of previously published STR loci in Ptig STRplex and contains a specific STR marker that confirms Panthera leo. An allelic ladder of all STR markers was prepared to enable reliable allele calling. The STR loci can also be used to type the DNA of other members of the genus Panthera. The work on the resulting STR profiles is performed using GenoProof Suite, which offers databasing, matching, and relationship analysis.
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... Es una actividad consuntiva controversial, pero aparentemente sostenible. Experiencias similares existen en otras partes del mundo como la cacería de alces (Alces alces) en Suecia (Gunnarsdotter, 2006) o leones (Panthera leo) en Tanzania (Whitman et al., 2004), así como con la pesca deportiva en muchas partes del mundo (Cooke et al., 2019). ...
Turismo sostenible, de naturaleza, de vida silvestre o ecoturismo, ¿qué acaso no son lo mismo?
Chapter
Full-text available
  • Mar 2025
La ambigüedad conceptual entre términos clave como “turismo sostenible”, “turismo de naturaleza”, “ecoturismo” y “turismo de vida silvestre” tiene implicaciones importantes en el contexto de América Latina. Mediante una revisión crítica de literatura académica, este capítulo explora las definiciones, alcances, diferencias y relaciones entre estos conceptos. Se plantea que esta falta de claridad dificulta la implementación de buenas prácticas turísticas en la región. Se conceptualiza al turismo sostenible como un enfoque –más que como un tipo de turismo– que equilibra las dimensiones ambiental, económica y sociocultural, sin degradar los recursos naturales o comunidades locales a través del tiempo. Por su parte, el turismo de naturaleza se realiza en áreas naturales protegidas o poco intervenidas. Mientras que el ecoturismo integra objetivos éticos, educativos y de generación de beneficios locales, representando una estrategia y un concepto normativo diferente al turismo de naturaleza convencional. Por otro lado, el turismo de vida silvestre se centra en el avistamiento y encuentros con animales no domesticados, en libertad o cautiverio, tanto en áreas naturales como urbanas, y pudiendo o no alinearse con los principios de sostenibilidad y los objetivos del ecoturismo. Se propone un modelo conceptual sobre las interrelaciones entre estos tipos de turismo y enfoques. Se destaca la necesidad de clarificar estos términos en español, que contribuyan a una mejor gestión turística en Latinoamérica, orientando teóricamente a diversos actores hacia prácticas turísticas responsables que promuevan la conservación y el desarrollo local. Palabras clave: Reflexión teórica, conceptualización, ambigüedad conceptual, sostenibilidad turística, Latinoamérica.
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... Estimates of breeding status are based on the relationship assignments in Program COLONY and age is from metadata collected from hunters at mandatory harvest check-in by Idaho Department of Fish and Game. Previous research has shown that breeders in group-living species have a disproportionate influence on group persistence and population growth (Whitman et al. 2004;Brainerd et al. 2008;Ausband et al. 2017a, b;Sparkman et al. 2017). Removing a breeder from these groups that breed once annually can directly (population size decreases by 1) and indirectly (population decreases because pack fails to reproduce) affect the population size and the subsequent recruitment. ...
Gray wolf breeders are more vulnerable to harvest during the breeding season
Article
Full-text available
  • Nov 2024
In cooperatively breeding carnivores, breeders are vital to perpetuating the group; the death or removal of an individual breeder can greatly affect group composition, genetic content, and short‐term population growth. Understanding the number of breeders harvested and timing of harvest can increase our knowledge of how mortality affects groups of cooperative breeders. Gray wolves (Canis lupus) in Idaho, USA, are exposed to annual harvest and are an ideal species for studying the effects of harvest on breeder turnover. We combined genotypes from tissue samples of harvested wolves with parentage analyses and cementum annuli ages and estimated when and how many breeding wolves were harvested. We genotyped and aged 229 adults and 203 pups using tissue and tooth samples from wolves harvested between 2014 and 2016. We identified a minimum count of 33 breeders in the harvest and found that they were disproportionately harvested more during the breeding season. We estimated that a minimum of ~14.5% of adult wolves harvested annually, or approximately 1 in 7, were breeders. We posit their behavior during breeding season may increase their vulnerability to harvest. By linking animal life history with vulnerability to human‐caused mortality we show that managers could structure harvest seasons so there is less overlap with wolves’ breeding season if there is concern about the demographic consequences of harvesting breeders.
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... If a suitor male defeats the dominant male, he becomes the new sire and kills any young cubs not of his lineage, bringing his own genes to the pride. The rotation of males within the pride takes place every 2 or 3 years, enabling a genetic mix that is highly beneficial to the conservation of the species (Nowell and Jackson, 1996;Whitman et al., 2004). Generally, relations between lions are peaceful, but conflicts can arise in times of famine. ...
Conservation of lion (Panthera leo Linnaeus, 1758) in West Africa : Ecological and anthropogenic determinant factors for its reintroduction in the Comoé National Park, Côte d'Ivoire
Thesis
Full-text available
  • Oct 2023
The twentieth century has been marked by an upsurge in anthropogenic activities, leading to significant changes in ecosystems worldwide. The consequence of these changes is the accelerating rate of biodiversity decline and species extinction. Current levels of anthropogenic disturbance are amplifying species extinction across ecosystems and regions, threatening the survival of many species, especially large carnivores e.g. the lion Panthera leo. Currently, because of these anthropogenic and environmental disturbances, all the lion’s populations are under serious threat in the African savannahs, and particularly in the Comoé National Park (CNP), where it has been extirpated for several years. Since 2010, numerous efforts have been made to conserve this ecosystem and its biodiversity, and the CNP management authority is considering reintroducing lions. Ideally, this reintroduction requires a prior understanding of fundamental factors. Thus, this study aimed at (1) assessing the community knowledge on factors behind lion extirpation in CNP; (2) determining lion carrying capacity based on current prey bases and available habitats in CNP; (3) evaluating the diversity and spatio-temporal distribution of current large predators in CNP; (4) identifying current threats to wildlife populations; and (5) assessing the Community perspectives on the prospect of lion reintroduction to CNP. Findings from this study will highlight current ecological potential of the CNP as well as the fundamental requirements to guide managers in large carnivores such as the lion reintroduction initiatives in West Africa. Semi-structured questionnaires were administered to 307 volunteer participants (i.e. respondents who gave us their prior verbal consent) in 23 surrounding villages of five sectors for sociological data collection. In addition, camera trapping and aerial survey methods were used to collect data on prey while monitoring patrols of OIPR eco-guards allow us to get data on anthropogenic disturbances. Sociological surveys revealed that lions were extirpated between 1998 and 2010 (19.75yr ± 8.15) from the Bouna sector around 1998 (mean = 23.61yr ± 9.14) and later on from the Nassian and Tehini sectors around 2003 (mean = 18.43yr ± 8.17; 18.74yr ± 6.74) with very weak correlation with respondent age (Pearson α = 0.01). People identified civil war from 2002 as indirect cause of lion extirpation (85%; n = 261), which led to the abandonment of CNP and opened the way for all direct causes i.e. illegal hunting and prey depletion (70%; n = 216), illegal gold mining (74%; n = 227), direct lion killing due to human-wildlife conflict (15%; n = 45), and wildfires (23%; n = 72). The spotted hyena and the leopard, current large carnivores in CNP totaled only 1.73% independent captures (n = 53), and were more nocturnal than diurnal with a high temporal overlap index (Oij (time) = 0.78). The kernel density estimation confirmed that spotted hyenas and leopard shared almost half of their activity patterns (Δ1=0.49 and 95% CI=0.26-0.71). Only Euclidian distance to nearest water point significantly influenced the detection probability of spotted hyena in CNP. Prey diversity is great in CNP but anthropogenic impacts seem represent potential threats that did not allow population growth of large predators. Unanimous, local community identified illegal gold mining (64%; n = 195), poaching (52%; n = 159), and human wildlife conflicts due attacks of wild animals (50%; n = 152) as main threats in CNP. Signs of poaching and gold mining were confirmed from camera trapping, and data from OIPR’s mobile brigade from 2018 to 2022 confirmed that illegal gold mining (68%; n = 5436), poaching (19%; n = 1486) and transhumance (2%; n = 162) were the main anthropogenic disturbance in CNP. Camera trapping revealed the presence of thirty-two (32) mammal species from thirteen (13) families including Bovidae (11), Felidae (02), Canidae (02), Herpestidae (03), Viverridae (02), Mustelidae (01), Suidae (02), Cercopithecidae (04), Galagidae (01), Hystricidae (01), Elephantidae (01), Hippopotamidae (01) and Orycteropodidae (01). Most detected prey species were kob antelopes, red-flanked duiker, hartebeest, bushbuck and bush duiker, but relatively average values were obtained for roan antelope and warthog. Anthropogenic and ecological factors influenced significantly prey presence in CNP. Using prey biomass from aerial survey, the lion-prey regression’ equations revealed that CNP could accommodate 173 lions (1.50 lion.100km-²) in undisturbed conditions, and 123 lions (1.07 lion.100 km-²) under disturbances. A large majority of respondents (73%, n=223) were in favor of the lion reintroduction with significant variance among ethnic groups (χ² = 39.95, df = 4 and p-value <0.05), and socio-professional categories (χ² = 19.34, Df = 7 and p-value <0.05). The generalized linear model (GLM) revealed that sex, profession, perceived benefits and risks, and an appreciation of the current management system were the main significant determinants for the acceptance of lion reintroduction in CNP. Our findings confirm that the current ecological state of the CNP as well as its species diversity and prey biomass allow the return of lions, and the sociological aspects and monitoring measures to secure the park are conductive. These results form part of a fundamental step in the direction for ethical reintroduction, as prescribed by the IUCN reintroduction specialist group. Going for the assumption that unsustainable hunting during the civil war period resulted in prey depletion and the lions extirpation in CNP, we recommend intensifying monitoring and local measures to limit anthropogenic disturbance and improving the involvement of indigenous communities. Conservation efforts are ongoing and we suggest CNP management to continue the implementation of actions to reduce sources of pressure, as well as improving the involvement of indigenous communities in potential reintroduction of lions, especially the pastoralists, and the sharing of any associated benefits. Key words: Acceptance of reintroduction; Anthropogenic pressures; Conservation of lion; Large carnivores; Lion carrying capacity; Species reintroduction; Comoé National Park.
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... The life-history strategy of delayed dispersal yields groups comprising multiple generations of offspring along with dominant breeders. Group size, composition, and genetic relatedness among individuals can affect the reproduction and survival of individuals in such groups (Courchamp and Macdonald 2001;Whitman et al. 2004;Gobush et al. 2008). ...
Helpers show plasticity in their responses to breeder turnover
Article
Full-text available
  • Jun 2024
Nonbreeding helpers can greatly improve the survival of young and the reproductive fitness of breeders in many cooperatively breeding species. Breeder turnover, in turn, can have profound effects on dispersal decisions made by helpers. Despite its importance in explaining group size and predicting the population demography of cooperative breeders, our current understanding of how individual traits influence animal behavior after disruptions to social structure is incomplete particularly for terrestrial mammals. We used 12 yr of genetic sampling and group pedigrees of gray wolves (Canis lupus) in Idaho, USA, to ask questions about how breeder turnover affected the apparent decisions by mature helpers (≥2-yr-old) to stay or leave a group over a 1-yr time interval. We found that helpers showed plasticity in their responses to breeder turnover. Most notably, helpers varied by sex and appeared to base dispersal decisions on the sex of the breeder that was lost as well. Male and female helpers stayed in a group slightly more often when there was breeder turnover of the same sex, although males that stayed were often recent adoptees in the group. Males, however, appeared to remain in a group less often when there was breeding female turnover likely because such vacancies were typically filled by related females from the males' natal group (i.e. inbreeding avoidance). We show that helpers exploit instability in the breeding pair to secure future breeding opportunities for themselves. The confluence of breeder turnover, helper sex, and dispersal and breeding strategies merge to influence group composition in gray wolves.
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... For example, an individual may bide its time and ultimately breed in its natal territory where it is already highly related to helpers in the group (Kokko and Ekman 2002). By contrast, usurping a breeder in a group can yield considerable social instability, increased dispersal of group members, and ultimately a smaller and less genetically related group (Whitman et al. 2004;Brainerd et al. 2008). ...
Lifetime reproductive characteristics of gray wolves
Article
  • May 2024
Female and male cooperative breeders can use different strategies to maximize reproduction and fitness over their lifetimes. Answering questions about fitness in cooperative breeders requires long-term studies as well as complete data on group composition and size which can be exceedingly difficult to obtain. Using a long-term genetic data set of complete group pedigrees, I asked how lifetime reproductive characteristics of female and male gray wolves (Canis lupus) differed. I predicted that genetic relatedness to helpers would be higher for females than males due to philopatric behavior of female wolves, group size would be similar between the sexes, females would inherit breeding positions from within groups more often than males due to differences in dispersal strategies between the sexes, males would have more lifetime mates and produce more young than females because of polygamy, and females would breed for more years than males due to the likelihood that females would still breed (with a new partner) after a mate died or was expelled from the group. I documented complete lifetime breeding histories for 11 male and 18 female wolves in Idaho, United States, 2008 to 2018. Genetic relatedness to helpers, group size, number of mates, pups, and years breeding did not differ between the sexes. Females, however, inherited breeding positions within groups far more often than males. Individuals who secured breeding positions generally reproduced for 2 seasons and commonly had more than 1 partner during their lifetimes if they were able to maintain their breeding position longer. Direct fitness varied greatly within female and male breeding wolves.
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... H uman actions commonly alter wildlife populations. A classic example is hunting, which often has density and demographic effects on a population [1][2][3][4] . Recreational quota-based hunting of carnivore populations is common across the globe 5,6 , however, the consequences of these actions on pathogen transmission and evolution are largely unknown and the few available studies report contradictory findings. ...
Hunting alters viral transmission and evolution
Preprint
  • Jan 2024
Hunting can fundamentally alter wildlife population dynamics, but the consequences of hunting on pathogen transmission and evolution remain poorly understood. Here we present a study that leverages a unique landscape-scale experiment coupled with pathogen transmission tracing, network simulation and phylodynamics to provide insights into how hunting shapes viral dynamics in puma (Puma concolor). We show that removing hunting pressure enhances the role of males in transmission, increases the viral population growth rate and the role of evolutionary forces on the pathogen (higher purifying and diversifying selection) compared with when hunting was reinstated. Changes in transmission could be linked to short term social changes as male population increases. These findings are supported through comparison with a region with stable hunting management over the same time period. This study shows that routine wildlife management can have profound impacts on pathogen transmission and evolution not previously considered.
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Sustainable exploitation: A review of principles and methods
Article
Full-text available
  • Sep 2001
Although the main theoretical framework determining how to exploit populations was derived almost 50 years ago, overexploitation is common. I review 10 major concepts underlying the regulation of exploitation: population increase can be exploited; density dependence is essential; quantifying density dependence is exceedingly difficult; sustainable exploitation involves reducing population size; population growth rate is usually mismeasured; sustainability has many conflicting definitions and the choice depends upon the objectives; it is better to monitor the population than the harvest; quotas are unstable; increasing effort is simple, reducing it is painful; exploit conservatively. I then give a brief account of each of the nine main methods that are used to determine sustainable exploitation and the uses, advantages and limitations of each. The nine techniques are: surplus production models, yield per recruit models, Robinson and Redford model, linking yield to recruitment and mortality, adjusting to population changes, comparing demography across sites, reducing to a fixed fraction of unexploited population size, full population models and adaptive management.
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Animal Breeding Systems, Hunter Selectivity, and Consumptive Use in Wildlife Conservation
Chapter
  • Aug 1998
In just the last few years, behavioral ecologists have begun to address issues in conservation biology. This volume is the first attempt to link these disciplines formally. Here leading researchers explore current topics in conservation biology and discuss how behavioral ecology can contribute to a greater understanding of conservation problems and conservation intervention programs. In each chapter, the authors identify a conservation issue, review the ways it has been addressed, review behavioral ecological data related to it, including their own, evaluate the strengths and weaknesses of the behavioral ecological approach, and put forward specific conservation recommendations. The chapters juxtapose different studies on a wide variety of taxonomic groups. A number of common themes emerge, including the ways in which animal mating systems affect population persistence, the roles of dispersal and inbreeding avoidance for topics such as reserve design and effective population size, the key role of humans in conservation issues, and the importance of baseline data for conservation monitoring and modeling attempts. Each chapter sheds new light on conservation problems, generates innovative avenues of interdisciplinary research, and shows how conservation-minded behavioral ecologists can apply their expertise to some of the most important questions we face today.
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Exploiting object-orientated programming structures in the quest for an individual-based lion population model with an attractive user interface
Article
  • Sep 2002
We present our most recent implementation of an individual-based lion population model. The model is built using a structure that includes graphical user interaction and feedback at a fundamental level, to maintain flexibility and ease of use without getting mired in programming details. We describe how object-orientated programming structures may be used to this end. Our structure allows for tight integration between the model and the user interface, including seamless user interaction at any point during the simulation. In addition, the simulation model may be decoupled from the user interface, and large, efficient simulations may be performed. The result is an individual-based model that, despite its complexity, is easy to use, easy to maintain and easy to extend. In fact, it has the potential to be used by a much wider group (including other researchers, managers and conservation advocates) than just the researcher who developed it. We include a discussion of the importance of a robust random number generator in simulation models such as this.
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The impact of tourist hunting on large mammals in Tanzania: An initial assessment
Article
  • Dec 1998
In Tanzania, where tourist hunting is employed as a conservation tool for habitat protection, information on population sizes and hunting offtake was used to assess the impact of tourist hunting on mammal densities. In general, tourist hunting pressure was unrelated to local population sizes, but for most species, animals were removed at a level of less than 10% of the local population size, suggesting that over-exploitation was unlikely. Eland, however, and perhaps small antelope, bushbuck, kudu and reedbuck were hunted at levels which may be unsustainable in the long term. Analyses also identified areas of Tanzania with high levels of tourist hunting pressure, showed that, in certain areas, species with small population sizes such as eland could be declining as a result of tourist hunting, and suggested that current levels of lion and leopard offtake are too high. These findings, although preliminary, allow recommendations to be put forward for changing hunting quotas for certain species in particular areas of Tanzania.
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Male takeovers and female reproductive parameters: A simulation of oestrous synchrony in lions (Panthera leo)
Article
  • May 1983
The takeover of a pride of lions by a new coalition of adult males synchronizes the reproductive states of the females because the females' dependent offspring either die or are evicted at the takeover. Using data on the consequences of male takeovers on female reproductive parameters in wild lions, but without allowing for any interaction between females, we simulated the reproductive histories of 100 female lions for the first 2 years after a male takeover and then cast them into simulated prides of varying sizes. The simulations produced levels of oestrous synchrony similar to those observed in prides of wild lions.
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Male lions in large coalition gain reproductive advantages
Article
  • Dec 1979
Cooperation between two or more individuals has been shown to yield short-term benefits in several vertebrate species1–4, and various hypotheses have been developed to explain the evolution of cooperative behaviour5–7. However, until now there has been no evidence to show that such cooperation actually does confer lifetime's reproductive advantages on more than one member of the coalitions concerned8,9. Long-term studies of wild lions (Panthera leo L.) have now provided such evidence. We show that, compared with singletons and pairs, male lions in groups of three or more can more reliably gain tenure of female prides, retain tenure for longer, mate with more different females, and produce more surviving offspring; thus each individual has higher fitness through cooperation.
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