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Hunting to extinction: Biology and regional economy influence extinction risk and the impact of hunting in artiodactyls



Half of all artiodactyls (even-toed hoofed mammals) are threatened with extinction, around double the mammalian average. Here, using a complete species-level phylogeny, we construct a multivariate model to assess for the first time which intrinsic (biological) and extrinsic (anthropogenic and environmental) factors influence variation in extinction risk in artiodactyls. Globally artiodactyls at greatest risk live in economically less developed areas, have older weaning ages and smaller geographical ranges. Our findings suggest that identifying predictors of threat is complicated by interactions between both biological and anthropogenic factors, resulting in differential responses to threatening processes. Artiodactyl species that experience unregulated hunting live in significantly less economically developed areas than those that are not hunted; however, hunted species are more susceptible to extinction if they have slower reproductive rates (older weaning ages). In contrast, risk in non-hunted artiodactyls is unrelated to reproductive rate and more closely associated with the economic development of the region in which they live.
Hunting to extinction: biology and regional
economy influence extinction risk and
the impact of hunting in artiodactyls
Samantha A. Price
and John L. Gittleman
Department of Biology, Gilmer Hall, University of Virginia, Charlottesville, VA 22904, USA
National Evolutionary Synthesis Center, 2024 W. Main Street, A200 Erwin Mills Building, Durham, NC 27705, USA
Half of all artiodactyls (even-toed hoofed mammals) are threatened with extinction, around double the
mammalian average. Here, using a complete species-level phylogeny, we construct a multivariate model to
assess for the first time which intrinsic (biological) and extrinsic (anthropogenic and environmental)
factors influence variation in extinction risk in artiodactyls. Globally artiodactyls at greatest risk live in
economically less developed areas, have older weaning ages and smaller geographical ranges. Our findings
suggest that identifying predictors of threat is complicated by interactions between both biological and
anthropogenic factors, resulting in differential responses to threatening processes. Artiodactyl species that
experience unregulated hunting live in significantly less economically developed areas than those that are
not hunted; however, hunted species are more susceptible to extinction if they have slower reproductive
rates (older weaning ages). In contrast, risk in non-hunted artiodactyls is unrelated to reproductive rate
and more closely associated with the economic development of the region in which they live.
Keywords: Artiodactyla; extinction; bushmeat; hunting;
economic development and phylogenetic comparative methods
Understanding the biological processes underlying species
extinction is one of the most important goals for
conservation biology, particularly for effective manage-
ment of populations and predicting species that require
immediate conservation measures (Mace & Balmford
2000). It has been shown in a variety of taxa, at both local
and global scales, that biological characteristics are
important determinants of variation in extinction risk
(see review by Reynolds 2002). To date, studies have
largely focused on overall correlates of extinction risk of
mammals (e.g. Purvis et al. 2000; Cardillo & Bromham
2001; Jones et al. 2003), while not assessing the complex-
ity of how different traits predispose species to extinction
via different threatening processes (Jennings et al. 1998;
Owens & Bennett 2000; Fisher & Owens 2004; Isaac &
Cowlishaw 2004; Keane et al. 2005).
Anthropogenic factors such as human population
density and economic development are expected to
correlate with extinction risk (e.g. Davies et al. 2006)
regardless of threatening process. Higher human densities
lead to higher levels of human impact on species and the
environment (e.g. McKee et al. 2004; Keane et al. 2005;
Davies et al. 2006) and have been found to be important in
explaining local and global extinctions (Brashares et al.
2001; Cardillo et al. 2004, respectively). Economic status
is also important; it affects how much governments can
spend on conservation efforts and how its people exploit
natural resources. The situation in economically less
developed countries often necessitates opportunistic and
short-term exploitation of the local flora and fauna by its
citizens, increasing the risk of local extinction (Rodriguez
2000; Matos & Bovi 2002). For example, gross domestic
product (GDP) is negatively related to the number of
threatened birds globally (Davies et al. 2006).
Habitat loss (including fragmentation and degradation)
and exploitation are the two major processes threatening
mammals today; they account for 46.6 and 33.9% of all
recorded threats, respectively (Mace & Balmford 2000).
Each threat process exerts fundamentally different selec-
tive pressures: exploitation acts directly upon the species
by increasing mortality while habitat loss acts indirectly by
reducing the carrying capacity of the environment. The
Artiodactyla (even-toed hoofed mammals) provide a
unique test case for evaluating the importance of hunting
because exploitation is the primary threatening process
responsible for 40% of recorded threats, while habitat loss
accounts for 36% (
Predictions concerning how species traits increase
susceptibility to exploitation can be divided into two main
categories: those pertaining to reproductive rates and those
related to hunter behaviour (see review by Fitzgibbon
1998). As an example, the Quaternary mammalian
megafauna extinctions have often been associated with
over-hunting and the spread of modern humans (see review
by Barnosky et al.2004), and both hunter selection of large-
bodied prey (blitzkrieg hypothesis, Martin 1984)andslow
reproductive rates (Johnson 2002) have been proposed as
determinants of the loss of mammal species.
Proc. R. Soc. B (2007) 274, 1845–1851
Published online 17 May 2007
Electronic supplementary material is available at
1098/rspb.2007.0505 or via
* Author and address for correspondence: National Evolutionary
Synthesis Center, 2024 W. Main Street, A200 Erwin Mills Building,
Durham, NC 27705, USA (
Present address: Institute of Ecology, University of Georgia, Athens,
GA 30602, USA.
Received 12 April 2007
Accepted 26 April 2007
1845 This journal is q 2007 The Royal Society
Hunters have been shown to prefer to hunt larger-
bodied species (Mittermeier 1987; Jerozolimski & Peres
2003), and the large body size has been found to correlate
with threat status in exploited birds (Owens & Bennett
2000; Keane et al. 2005) and hunted primates (Isaac &
Cowlishaw 2004). However, the harvest rate may reflect
the encounter rate, which is controlled by hunter
numbers, hunter behaviour and prey biology (Fitzgibbon
1998). Increasing size is also associated with slow
reproductive rates, which increase vulnerability to extinc-
tion via hunting. The principle of sustainable harvesting
(Hartig 1796; Clark 1990) suggests that a population will
remain stable even when individuals are harvested as long
as off-take does not exceed rN(1KN/K ), where N is the
population size, K is the carrying capacity and r is the
intrinsic rate of population growth. Therefore, species
with fast rates of increase (r) will have a larger surplus
available for harvesting and should be more resilient to
increased mortality (Bodmer 1995; Bodmer et al. 1997;
Jennings et al. 1998). Thus, traits that reflect reproductive
speed such as weaning age, age at sexual maturity and
body mass will potentially show an association with
extinction risk via exploitation (Owens & Bennett 2000;
Purvis 2001; also see reviews by Cowlishaw & Dunbar
2000; Kokko et al. 2001).
Here, we have constructed a multivariate phylogenetic
regression model to identify the biological, ecological and
anthropogenic variables that correlate with levels of threat
across the Artiodactyla as given by the IUCN Red List
(sensu Purvis et al. 2000). We then investigated whether
different traits elevate the risk of extinction depending on
whether a species is hunted or not. The majority of
artiodactyls are hunted for food, often termed bushmeat
hunting, while others are hunted as trophies (e.g. Urial
sheep, Ovis vignei; sable antelope, Hippotragus niger) or for
their soft hair (e.g. chiru, Pantholops hodgsoni ). The
analyses were repeated with the dataset partitioned into
two: the hunted species forming one partition and the
species that we could not validate as being hunted forming
the other ‘non-hunted’ partition.
The IUCN (2006) Red List (IUCN 2006) was used as the
measure of current extinction risk. The Red List categories
were divided into six levels (following Purvis et al. 2000): least
concern, 0; near threatened, 1; near threatened conservation
dependent and vulnerable, 2; endangered, 3; critically
endangered, 4; extinct in wild and extinct, 5, although no
extinct species were added to the analysis. To ameliorate the
effect of autocorrelation between species traits and the criteria
for IUCN classification, all analyses were performed on
species whose Red List classification was based on a decline in
population density or geographical range size (criterion A),
rather than the absolute measures of those variables. After the
data deficient species and those not classified under criterion
A were removed, 144 artiodactyl species categorized from
least concern to critically endangered were available for
analysis (electronic supplementary material).
Eleven predictor variables were chosen to represent the
anthropogenic, hunter behaviour and reproductive rates
hypotheses (summarized in table 1). Five additional variables
were also included to represent other commonly cited
hypotheses concerning elevated extinction risk: small popu-
lation size as indicated by small geographical range and low
population density (e.g. Gaston 1994); poor ecological
flexibility (e.g. Brown 1971; Laurance 1991) as represented
by narrow habitat breadth and dietary specialization; and,
finally, large home ranges which make species especially
vulnerable to habitat loss (e.g. Woodroffe & Ginsberg 1998).
Thirteen quantitative traits were obtained from the
ANTHERIA trait database ( K. E. Jones, J. Bielby, A. Purvis,
D. Orme, A. Teacher, J. L. Gittleman, R. Grenyer, et al.,
unpublished manuscript): weaning age; maximum lifespan;
gestation length; age at first birth; inter-birth interval; age at
sexual maturity; home range; body mass; group size;
population density; geographical range; mean human popu-
lation density; and actual evapotranspiration (AET). AET
was included as a measure of primary productivity, which is
thought to be a confounding factor when using mean human
population density (Balmford et al. 2001). The database is the
product of a collaborative effort to construct a comprehensive
Table 1. Summary of hypotheses.
traits predicted to be associated with an elevated
risk of extinction explanation
anthropogenic high human population density higher human population densities lead to higher
levels of influence on species and the environment.
low gross national income lower national income necessitates opportunistic and
short-term exploitation of the local flora and fauna
by its citizens, increasing the risk of local extinction.
hunter behaviour large body mass hunters prefer to hunt larger species.
large group size larger groups are more visible to hunters.
polygamy polygamous mating systems require larger groups and
are therefore more visible. However, polygamous
mating strategies may also be associated with lower
threat as not all males are required for breeding
success; this requires selective hunting of non-
breeding males.
slow reproductive rate as indicated by older weaning
ages, longer gestation lengths, longer inter-birth
intervals, older ages at first birth and older ages at
sexual maturity
species with slow rates of increase (r) have smaller
surpluses available for harvesting and are therefore
less resilient to increased mortality from hunting.
large body mass and greater maximum longevity larger body masses and greater lifespans are
associated with slower reproductive rates.
1846 S. A. Price & J. L. Gittleman Hunting to extinction
Proc. R. Soc. B (2007)
database of major biological traits for all mammal species;
information is drawn from both primary and secondary
sources. All quantitative data used in this analysis represent
central tendency measures for each species and were C1
natural log transformed.
Gross national income (GNI; US $ millions) taken from
UNEP (2006) was added as an indicator of the socio-
economic condition experienced by a species across its range.
The 2003 estimates of GNI were used unless unavailable; the
most recent estimate was then used. Using A
weighted average of GNI across the species range was
calculated from country estimates of GNI and the area of
the species range (km
) in each country (ranges taken from
Sechrest 2003). Three categorical traits were collected from
the literature: mating strategy (polygamous, monogamous);
diet (specialist (grazer or browser) or generalist (mixed
grazer/browser or omnivore)); and habitat breadth. Habitat
breadth can vary between the levels 1 and 6 and was
calculated from the dataset presented in Caro et al. (2004),
which lists a species as living in as many as six different
habitats (grassland/scrubland, dense forest, desert, rocky,
tundra and swamp). All data were converted to the taxonomy
of Grubb (1993) and are available in the electronic
supplementary material.
The artiodactyl dataset of 144 species was used to identify
traits that correlate with extinction risk across artiodactyls.
The complete dataset was then partitioned on the basis of
threatening process and reanalysed to look for the differences
between traits that predispose hunted and non-hunted
species to extinction. Literature searches (Web of Science,
Biological Abstracts and Zoological Record) using the terms
Artiodactyl and hunting or bushmeat were used to identify
species that are known to be hunted, and we also followed up
citations in the papers found during the literature search. If
the only citations we could find referred to regulated hunting
then that species was not added to the hunted partition, e.g.
Ovis dalli. It is important to exclude species that only
experience regulated hunting from the hunted partition as,
theoretically at least, hunting should not be a threatening
process if appropriate quotas are set and enforced. We
identified 111 artiodactyl species that are cited within the
primary and secondary literature as being hunted without
regulation; 94 of these were classified under criterion A in the
IUCN Red List (IUCN 2006). The list of hunted species is a
conservative estimate of the species hunted worldwide.
Species that have experienced over-hunting in the past, but
are now protected, are not included, and species with small
geographical ranges are likely to be under-represented in our
sample, as we are restricted to the species that live within the
areas where studies of hunting have been undertaken.
All statistical analyses were conducted in R (http://www. on phylogenetically independent contrasts
(PICs; Felsenstein 1985), as the majority of traits showed
phylogenetic patterning using Pagel’s l-statistic (results not
shown; Pagel 1999). The topology presented in Price et al.
(2005) was used to generate the PICs. Independent contrasts,
including the modified version for categorical traits, were
calculated in R ( using the A
package (Paradis) and code provided by Andy Purvis, David
Orme and Rich Grenyer (P
ENDEK package in development,
available upon request from The
independent contrasts were standardized using branch
lengths (taken from Bininda-Emonds et al. 2007), which
were then transformed on a trait-by-trait basis following
Garland et al. (1992). Polytomies in the phylogeny were
treated as soft; they were resolved arbitrarily and the resulting
n contrasts from each down-weighted by 1/n, with each
node thereby contributing one degree of freedom (following
Purvis & Garland 1993).
We used a three-stage process to identify correlates of
extinction risk in all three data partitions (complete
artiodactyl dataset, hunted partition and non-hunted
partition). The first stage involved regressing IUCN threat
rating against each continuous predictor variable; although
threat is a discrete variable, a continuous distribution
underlies the categories (Purvis et al. 2000). To test the
effect of treating threat as a continuous variable, we ran
analyses with IUCN threat category converted to a binary
response variable (non-threatened, least concern and near
threatened; threatened, near threatened conservation depen-
dent through to critically endangered) with each life-history
trait in turn as the Y variable. Trait values were not available
for every species (electronic supplementary material), which
meant that sometimes the degrees of freedom were quite low
(10–20 degrees of freedom); however, no analysis was run
without at least 10 degrees of freedom. Body mass was added
as a covariate to all analyses that included weaning age, home
range, population density, age at first birth, inter-birth
interval and gestation length, as preliminary analysis
confirmed that they covaried with body mass. Collinearity,
however, should not be a problem as all correlations between
traits and body mass indicated R-squared values of under
0.40. AET, as a measure of primary productivity, was added
to all analyses including mean human population density, as
preliminary analysis confirmed that it had the potential to be a
confounding factor due to its significant association with
mean human population density. Categorical data were
analysed using the Wilcoxon signed-rank test on the
contrasts. The second stage involved repeating the regression
analyses including geographical range to allow comparisons
to previous mammalian extinction risk analyses (Purvis et al.
2000; Jones et al. 2003). During each of these stages, the
regressions were plotted, and contrasts that had undue
influence over the regression line were deleted. Finally, the
third stage involved building a multivariate regression model
for each data partition that included all significant ( p!0.05)
and marginally significant ( p!0.1) continuous traits from
the first two stages. This regression model formed the starting
set for model simplification to find the minimum adequate
model (MAM), following the procedure outlined in Purvis
et al. (2000).
(a) Artiodactyla
Of the 144 artiodactyls that are categorized under
criterion A in the IUCN Red List, 67 are currently
threatened with extinction. Biological, ecological and
anthropogenic correlates of extinction risk across all
artiodactyls are presented in table 2. When single traits
were regressed against threat status, small geographical
range, older weaning age and low GNI were all
significantly associated with a higher risk of extinction.
When geographical range was added to the regression
model, weaning age lost some significance and population
density became marginally significant. The MAM
(table 3) revealed weaning age, population density and
GNI as the important predictors of extinction risk in
Hunting to extinction S. A. Price & J. L. Gittleman 1847
Proc. R. Soc. B (2007)
the Artiodactyla, explaining 36.2% of the variance.
Geographical range explains 6.9% but loses significance
when placed in a multivariate model with weaning age
(d.f.Z60, tZK0.885, pZ 0.38). None of the three
categorical traits showed a significant relationship with
threat category.
When the effect of threat distribution was removed
using the dichotomous threat variable, older weaning was
confirmed as the most significant predictor of elevated
threat (VZ168, pZ0.002). GNI was confirmed as an
important predictor of threat (VZ117, pZ0.051); species
that live in economically less developed countries are
more threatened. Larger body mass and longer gestation
length showed associations with higher threat (body
mass VZ299, pZ0.079; gestation VZ232, pZ0.063),
while geographical range (VZ190.5, pZ1) and popu-
lation density (VZ101, pZ0.8) showed no significant
predictive ability.
(b) Hunted and non-hunted species
Approximately 50% of the species in each partition are
threatened with extinction. Traits that are associated with
elevated threat levels in hunted artiodactyls are different
from those that increase vulnerability to extinction in
artiodactyls that are not known to experience uncontrolled
hunting (table 4). In the first two stages of the analysis,
weaning age and geographical range were the only
significant predictors of threat status in hunted species,
while age at first birth and population density were nearly
significant ( p!0.1). The MAM for the hunted partition
contains only weaning age, which explains 19.7% of the
variance in threat rating. By contrast, in the analysis of the
non-hunted partition, geographical range, population
density and GNI were significantly correlated with threat
status, although population density lost significance when
geographical range was added to the model. The MAM for
the non-hunted partition contains both geographical range
and GNI and explains 26.8% of the variance in threat
rating. None of the categorical traits were significantly
related to threat status in either partition (results not shown);
the degrees of freedom are very low (d.f.!12).
Our analyses confirm the prediction that the influence of
particular threatening processes on extinction risk
depends on species-specific biological and ecological
traits. Traits that were significant predictors of extinction
risk across artiodactyls segregated among the hunted and
non-hunted processes; geographical range was the only
trait to remain significant regardless of threatening
process. This result contrasts the comparative analyses
of exploited primates and carnivores, which show the same
set of extinction risk correlates across all species regardless
of threat process (Purvis 2001).
Although geographical range was the only trait
significantly associated with extinction risk in all dataset
partitions, weaning age appears to be the key determinant
of artiodactyl threat rating. Weaning age explains the
greatest amount of variance in artiodactyl threat rating
Z11%) and, unlike geographical range, weaning age is
retained in the artiodactyl MAM and remains significant
when threat is treated as a binary variable (threatened or
non-threatened). This finding is not consistent with other
studies in which geographical range is the single most
important predictor of global mammalian extinction risk
(carnivores and primates, Purvis et al. 2000; marsupials,
Cardillo & Bromham 2001; bats, Jones et al. 2003). The
greater importance placed on a reproductive trait in
artiodactyls may relate to the fact that artiodactyls are
primarily threatened by hunting (Mace & Balmford
2000), and weaning age is only associated with extinction
in hunted artiodactyls. The mechanism for this result may
be that hunted artiodactyls are more prone to extinction if
they wean at older ages, a conclusion which is consistent
with the prediction based on sustainable yield theory
(Hartig 1796; Clark 1990). Species with older weaning
ages have slower reproductive rates and, consequently,
Table 3. Minimum adequate models (MAMs). (
p!0.001; n.s., not significant; - - -, trait not
added to the model as not significant in the single predictor
Artiodactyla hunted non-hunted
d.f. 45 43 35
0.3637 0.1974 0.2684
geographical range n.s. n.s. K2.462
body mass n.s. n.s. n.s.
weaning age 4.452
population density K2.094
n.s. n.s.
age at first birth - - - n.s. - - -
gross national
--- K2.968
mean human
n.s. - - - - - -
Table 2. Correlates of extinction risk: complete artiodactyl
dataset. (
trait d.f.
sole predictor
(t-statistic) d.f.
phical range
94 K2.841
adult body mass 99 0.852 93 1.506
home range
44 1.088 42 0.352
72 K1.37 68 K1.959
gestation length
86 0.276 82 0.132
age at first birth
48 0.062 46 K0.291
55 0.689 53 0.338
weaning age
63 2.685
59 2.281
sexual maturity
70 K0.219 67 K0.519
81 K0.067 77 0.37
social group size
57 K0.177 56 K0.419
habitat breadth 96 K0.95 91 K0.727
mean human
95 K0.169 92 K0.052
gross national
96 K2.456
93 K2.785
Bodymass was added as a covariate.
Actual evapotranspiration (AET) was added as a covariate.
1848 S. A. Price & J. L. Gittleman Hunting to extinction
Proc. R. Soc. B (2007)
have lower sustainable off-takes, making them more prone
to extinction via unsustainable harvesting. Our conclusion
that the global extinction of hunted artiodactyls is related
to slow reproductive rate is congruent with evidence from
local extinctions of hunted mammals (Bodmer et al. 1997)
and studies of bushmeat hunting, which show that slow-
growing species are being hunted unsustainably (e.g.
Barnes 2002; Bennett et al. 2002; Fa et al. 2003).
There is no evidence that hunter behaviour is playing a
role in determining global artiodactyl extinction risk;
hunter preference for large body size and hence slow life-
history traits (e.g. Isaac & Cowlishaw 2004) cannot
explain our results as body mass is not a significant
predictor of threat. Our conclusion that present vulner-
ability to hunting-induced extinction is related to slow
reproductive rates, not hunter preference for body size, is
consistent with recent conclusions regarding the
determinants of past exploitation-related extinctions
(Johnson 2002). Extrapolation from extant relatives of
species that went extinct during the Late Quaternary
mammalian ‘megafaunal extinctions has shown that
species with slow reproductive rates were more likely to
become extinct regardless of body size (Johnson 2002).
GNI was a significant predictor of threat across all
artiodactyls: species that live in areas of low economic
development are more threatened. These findings agree
with the results from a recent study (Davies et al.2006)on
the global distribution of extinction risk in birds, wherein
areas of high economic development (as measured by GDP)
are coincident with lower numbers of threatened species
worldwide. When the dataset was partitioned, GNI was only
associated with threat status in non-hunted artiodactyls,
which contradicts our prediction that a weak economy will
elevate the threat of extinction for all species regardless of
threatening process. Although the threat status of hunted
species is not associated with national economic status, risk
of being hunted is associated with GNI: artiodactyls that
experience uncontrolled hunting live in areas with signi-
ficantly lower GNI than non-hunted species (Mann–
Whitney test, WZ5889, pZ3.047!10
). It is perhaps
not surprising that species that experience unregulated
hunting live in countries with low GNI because regulation
(setting and enforcing quotas, etc.) of hunting is costly.
Thus, the exclusion of artiodactyls that experience only
regulated hunting may actually prevent us from seeing a
relationship between threat status and GNI in the hunted
with higher GNI.
Species that are in the ‘non-hunted’ partition are likely to
be primarily threatened by habitat loss, as it is the second
most important threatening process in artiodactyls,
accounting for 36% of all threats ( Several
hypotheses are commonly associated with extinction due to
habitat loss: those reflecting ecological flexibility (Brown
1971; Laurance 1991; Norris & Harper 2004; but see
Vazquez & Simberloff 2002) and those associated with small
population size (Te r b or gh 1 9 74 ; Simberloff 1986; Owens &
Bennett 2000; Koh et al.2004). Low population densities
and small geographical ranges are associated with extinction
risk in non-hunted artiodactyls, which is consistent with the
small population hypothesis, but neither of the traits that
reflect ecological flexibility, dietary specialization and
habitat breadth, is associated with threat.
We conclude that different biological traits elevate
vulnerability to extinction in artiodactyl species depending
on whether a species is hunted. Correlates of extinction
risk across all artiodactyls are a composite of the traits that
increase vulnerability to different threats. Hunted artio-
dactyls with slower reproductive rates are more at risk of
extinction, even though artiodactyls per se are less
vulnerable than primates to extinction via hunting due to
their relatively fast rates of reproduction (Bodmer et al.
1997). It is therefore important to know what type of
threat a species is facing, particularly whether it is hunted
or not, before identifying correlates of extinction risk. This
study is an initial step in understanding how artiodactyls
respond to anthropogenic extinction processes; the effects
of habitat loss and hunting are often synergistic (Peres
2001). To improve the predictive ability of our extinction
risk models, future studies must quantify how species
Table 4. Correlates of extinction risk: hunted and non-hunted partitions. (
hunted species non-hunted species
sole predictor
(t-statistic) d.f.
with geographical
range (t-statistic) d.f.
sole predictor
(t-statistic) d.f.
with geographical
range (t-statistic)
geographical range 62 K3.365
—— 36 K0.2743
adult body mass 64 0.668 61 1.359 38 0.226 35 0.185
home range
24 K0.478 21 K0.626 20 0.616 18 K0.091
population density
42 K0.562 41 K1.832
25 K2.191
22 K1.945
gestation length
58 0.832 56 0.549 31 0.469 28 0.403
age at first birth
31 1.996
28 0.505 32 0.46 29 0.984
inter-birth interval
34 1.014 32 K0.103 22 K0.154 19 K0.256
weaning age
43 3.439
39 2.554
23 0.296 21 0.393
sexual maturity age
45 1.596 43 0.693 28 K0.171 25 0.07
maximum longevity
50 K0.488 48 K0.713 33 0.335 29 0.984
social group size
38 1.194 36 1.061 15 K1.541 14 K1.749
habitat breadth 60 K0.176 59 K0.899 38 K0.085 35 0.9227
mean human popu-
lation density
63 K0.225 60 0.055 35 K1.068 34 K0.383
gross national income 63 K0.716 61 K0.205 36 K2.888
35 K2.968
Bodymass was added as a covariate.
Actual evapotranspiration (AET) was added as a covariate.
Hunting to extinction S. A. Price & J. L. Gittleman 1849
Proc. R. Soc. B (2007)
respond to multiple extinction threats (Isaac & Cowlishaw
2004) and determine the spatial and/or temporal variation
in the different threats ( Fisher & Owens 2004).
We thank Andy Purvis, Rich Grenyer and David Orme for
supplying the ‘R’ code for the phylogenetic independent
contrast analysis, Hilmar Lapp for help with ‘R’, Georgina
Mace, Rich Grenyer, Jonathan Davies and Jessica Partain for
helpful discussion, Andy Purvis and two anonymous
reviewers for comments and suggestions on earlier drafts of
the manuscript, and Kate Jones for help with P
and comments on a more recent draft of the manuscript.
Financial support was received from the National
Science Foundation (DEB/0129009) and latterly a NESCent
post-doctoral fellowship to S.A.P. (NESCent NSF
no. EF-0423641).
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... Studies have shown that large body sizes in mammals are proportional to slow population growth rates, which increase the probability of extinction, especially due to poaching/hunting practices (Price & Gittleman 2007). We found that four of the five most threatened wetland mammal species (sangai, swamp deer, wild Asian buffalo, and Indian hog deer) were herbivores with body weights >100 kg (Appendix S8). ...
... Habitat destruction and the exploitation of vertebrate species are considered to be primary 'twin extinction threats' around the globe (Ripple et al. 2016). Hunting and poaching directly slow the population growth rate and accelerate the mortality rate of a species, while habitat destruction indirectly reduces the carrying capacity of the environment (Price & Gittleman 2007). Our extensive literature review showed that habitat loss and fragmentation due to various development activities were the primary anthropogenic threats for all 11 wetland mammals. ...
en • Environmental change and anthropogenic pressure are primary drivers of biodiversity loss, particularly in wetland ecosystems that have been modified significantly. Among wetland specialists, mammals may be particularly vulnerable to extinction. We aimed to increase understanding of threats and knowledge gaps faced by 11 mammal species inhabiting wetlands throughout India. • We adopted a systematic literature search protocol following an evidence‐based conservation approach to obtain information on conservation threats and identify knowledge gaps for each species. Each species received threat scores based on the occurrence and magnitude of ecological and anthropogenic threats, a score based on its International Union for Conservation of Nature (IUCN) Red List category, and a knowledge gap score. A cumulative conservation threat score based on the four individual scores was calculated for each species to assess overall conservation threats. • Only about 10% of the literature search results were relevant. Of the major research categories, ecology was the most well‐studied, whereas the impact of anthropogenic pressure on wetland mammals was the least studied. Pressing ecological and anthropogenic threats, scientific knowledge gaps, and conservation needs contributed to a high cumulative threat score for the sangai Rucervus eldii eldii (cumulative threat score = 34), followed by the wild Asian buffalo Bubalus arnee (threat score = 33) and the Bengal marsh mongoose Herpestes palustris (threat score = 32). Poaching/hunting, habitat loss due to development, and changes in land‐use practices were found to be the major anthropogenic threats resulting in decreasing population trends. We identified knowledge gaps concerning the ecology of wetland mammals (e.g. population abundance). It is essential that these knowledge gaps are filled for effective conservation planning. • We identified important areas (population ecology, disease ecology, human–wildlife conflict, changes in land use) that should be considered as research priorities for wetland mammals in India, in order to make conservation efforts more effective and enable management planning, to ensure the long‐term survival of these mammals. Zusammenfassung auf Deutsch de • Umweltveränderungen und anthropogener Druck sind Haupttreiber für den Verlust der biologischen Vielfalt, insbesondere in Feuchtgebieten, die erhebliche ökosystemare Veränderungen erfahren haben. Unter den Feuchtgebietsspezialisten sind Säugetiere möglicherweise besonders vom Aussterben bedroht. Ziel unserer Studie war es, das Verständnis von Bedrohungen und Wissenslücken für 11 Säugetierarten in Feuchtgebieten Indiens zu verbessern. • Wir haben eine systematische Literaturrecherche anhand von evidenzbasierten Schutzansätzen durchgeführt, um Informationen über Bestandsbedrohungen zu erhalten und Wissenslücken für Arten zu identifizieren. Jede Art erhielt Gefährdungsbewertungen basierend auf dem Auftreten und dem Ausmaß ökologischer und anthropogener Bedrohungen, eine Bewertung auf Grundlage der Roten Liste der Internationalen Union für Naturschutz (IUCN) sowie eine Bewertung der Wissenslücken.Für jede Art wurde eine kumulative Bewertung der Schutz Bedrohung basierend auf den vier Einzelbewertungen berechnet, um die Gesamtbedrohungen für die Erhaltung zu bewerten. • Nur etwa 10% der Ergebnisse der Literaturrecherche waren relevant. Von den wichtigsten Forschungskategorien war die Ökologie am besten untersucht, der Einfluss des anthropogenen Drucks auf Säugetiere in Feuchtgebieten am wenigsten. Der ökologische und anthropogene Gefährdungsdruck, wissenschaftliche Wissenslücken und Schutzbedürftigkeit trugen zu einem hohen kumulativen Gefährdungswert für den Sangai Rucervus eldii eldii (kumulativer Gefährdungswert = 34) bei, gefolgt vom wilden asiatischen Büffel Bubalus arnee (Gefährdungswert = 33) und dem Bengalischer Sumpfmungo Herpestes palustris (Gefährdungswert = 32) bei. Wilderei/Jagd, Verlust des Lebensraums aufgrund der regionalen Entwicklung sowie Änderungen der Landnutzung erwiesen sich als die größten anthropogenen Bedrohungen, die zu negativen Trends der Populationsentwicklung führten. Wir konnten Wissenslücken hinsichtlich der Ökologie von Säugetieren der Feuchtgebiete (z.B. Bestandszahlen) identifiziert. Für die Entwicklung von effektiven Schutzstrategien müssen diese Wissenslücken geschlossen werden. • Wir haben wichtige Gebiete (Populationsökologie, Krankheitsökologie, Mensch–Wildtier Konflikt, Landnutzungsänderungen) identifiziert, die als Forschungsprioritäten für Säugetiere der Feuchtgebiete in Indien betrachtet werden sollten, um die Schutzbemühungen effektiver zu gestalten und eine Managementplanung zu ermöglichen, die ein langfristiges Überleben dieser Säugetiere sichert.
... In Sub-Saharan Africa, illegal exploitation and trade in forest resources (e.g. timber and bushmeat) have serious implications for biodiversity conservation and ecosystem services (Price & Gittleman, 2007). Such deleterious implications are exacerbated by current trends of deforestation levels, as observed in West Africa where at least 22% of the forest surface is degraded by human activities (FAO & UNEP, 2020). ...
... It is reasonable to suggest that a combination of habitat degradation and reduced forested cover is the main factor explaining the low density of medium-sized mammals in the forest islands surrounding LNF (Bogoni et al., 2020;Tilker et al., 2019). Preferential hunting for prized, medium-sized mammals which are the largest mammals occurring in southern Benin could also have exacerbated this trend (Price & Gittleman, 2007), but data to support this hypothesis are currently lacking. ...
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Illegal hunting of wildlife is one of the major issues in tropical ecosystems, especially when it occurs in highly degraded habitats with forest cover fragmentation. In this study, we assessed the impact of bushmeat hunting in a large forest patch (the Lama Natural Forest; LNF) and 11 nearby forest islands, using Traditional Ecological Knowledge from 240 interviewees across 16 villages. Thirty-five species belonging to nine orders of mammals, birds and reptiles were mentioned by local communities. Rodentia were significantly more observed in the forest islands, whereas medium-sized mammals belonging to Carnivora, Primates, Artiodactyla, Pholidota and Hyracoida were found predominantly in LNF. Approximately 57% of the species were reported to be rare in the forest islands, whereas c. 77% were listed as abundant in LNF, confirming the role of LNF as a refuge for forest species targeted by the bushmeat trade. Generalised linear models indicated that species sighting frequencies were positively correlated with perimeters of forest patches. We found hunting pressure to be greater in forest islands in the vicinity of LNF than those further away. Our results suggest that long-term conservation of wildlife in southern Benin may require a ‘mainland-islands’ approach including both LNF and its surrounding forest islands.
... First, it may be that this trait is truly inconsistent across taxa. For example, among mammals, diet specialists have been shown to be more at risk within bats (Boyles and Storm, 2007) but not within artiodactyls (Price and Gittleman, 2007). Alternatively, the data that were available for this trait was not the best proxy of dietary specialization. ...
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Species differ in their biological susceptibility to extinction, but the set of traits determining susceptibility varies across taxa. It is yet unclear which patterns are common to all taxa, and which are taxon-specific, with consequences to conservation practice. In this study we analysed the generality of trait-based prediction of extinction risk across terrestrial (including freshwater) vertebrates, invertebrates and plants at a global scale. For each group, we selected five representative taxa and within each group we explored whether risk can be related to any of 10 potential predictors. We then synthesized outcomes across taxa using a meta-analytic approach. High habitat specificity was a consistent predictor across vertebrates, invertebrates and plants, being a universal predictor of risk. Slow life-history traits-large relative offspring size, low fecundity, long generation length-, and narrow altitudinal range were also found to be good predictors across most taxa, but their universality needs to be supported with additional data. Poor dispersal ability was a common predictor of extinction risk among invertebrate and plant taxa, but not consistently among vertebrates. The remaining traits (body size, micro-habitat verticality, trophic level, and diet breadth) were useful to predict extinction risk but only at lower tax-onomical levels. Our study shows that despite the idiosyncrasies among taxa, universal susceptibility to extinction exists and several traits might influence extinction risk for most taxa. Informing conservation prior-itization at lower taxonomic scales should however include taxon-specific trait-based predictors of extinction risk.
... This period was marked by the progressive decrease or even sometimes the extinction of wild animal species, as the latter were either affected by human-induced environmental changes or by excessive hunting to meet the needs of growing human populations. This decline was also due to an increase in symbolic behaviour related to food production and social organization (Akkermans & Schwartz, 2003;Price & Gittleman, 2007). Hunting activities intended to trap mobile herds (with mega-traps) or solitary wild game are pre-planned and require group or community organization (well thought-out strategies); adapted hunting techniques for capturing an animal (process); knowledge of regional ecology and animal ethology (know-how); and a specific need and/or desire for the outcome (decision-making) (Chahoud et al. in prep.). ...
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For almost a century there has been debate on the functional interpretation of desert kites. These archaeological structures have been interpreted as constructions for animal hunting or domestication purposes, sometimes for both, but with little conclusive evidence. Here, we present new evidence from a large-scale research programme. This unprecedented programme of archaeological excavations and geomatics explorations shows the unequivocal and probably exclusive function of kites as hunting traps. Considering their gigantic size, as well as the signifcant energy and organization required to build them, these types of traps are called mega-traps. Our research is based on fve diferent feld studies in Armenia, Jordan, Kazakhstan and Saudi Arabia, as well as on satellite imagery interpretation across the global distribution area of kites throughout the Middle East, the Caucasus and Central Asia. This hunting interpretation raises questions about the transformation of the landscape by human groups and the consequent anthropogenic impacts on local ecological equilibrium during different periods of the Holocene. Finally, the role of trapping in the hunting strategies of prehistoric, protohistoric and historic human groups is addressed.
... Conservation scientists studying the drivers of biodiversity loss are aware of the oft-cited reasons for human-influenced species declines: habitat loss and fragmentation (Tilman et al. 1994), climate change (Cahill et al. 2013), overharvesting (Price and Gittleman 2007), alien species (Dextrase and Mandrak 2006), disease (Rödder et al. 2009) and pollution (Bobbink et al. 1998). But these are proximate rather than ultimate drivers of global change; our consumption and population size, density and growth underlie these all. ...
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The world is changing more quickly now than it ever has before, predominantly due to our large consumption rates and population size. Despite this epoch being well-accepted as the 'Anthropocene', it is surprising that there is still a lack of willingness by many conservation scientists to engage with the consequences of human population dynamics on biodiversity. We highlight the importance of addressing the effects of our population abundance, density and growth rate on conservation and note that environmental organisations are beginning to embrace this problem but the take-up amongst conservation researchers to empirically study their effect on biodiversity is slow. We argue that the lack of published research may partly be because the topic is still considered taboo. We therefore urge conservation scientists to direct more of their research efforts on this issue, particularly to examples that highlight the effects of Population, Health and Environment (PHE) projects and female education initiatives on biodiversity.
... Mean annual temperature and human population density were excluded from analyses because they had lower explanatory power in predicting extinction risk than their highly correlated variables (Table 2). Third, we selected potential important predictors (P < 0.1) identified in the first step and built a set of candidate models considering all possible combinations of these variables (Price and Gittleman 2007;Chen et al. 2019a). Fourth, we used the corrected Akaike information criterion (AICc) and the Akaike weight (w i ) to rank candidate models. ...
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China is a country with one of the most species rich reptile faunas in the world. However, nearly a quarter of Chinese lizard species assessed by the China Biodiversity Red List are threatened. Nevertheless, to date, no study has explicitly examined the pattern and processes of extinction and threat in Chinese lizards. In this study, we conducted the first comparative phylogenetic analysis of extinction risk in Chinese lizards. We addressed the following three questions: 1) What is the pattern of extinction and threat in Chinese lizards? 2) Which species traits and extrinsic factors are related to their extinction risk? 3) How can we protect Chinese lizards based on our results? We collected data on ten species traits (body size, clutch size, geographic range size, activity time, reproductive mode, habitat specialization, habitat use, leg development, maximum elevation, and elevation range) and seven extrinsic factors (mean annual precipitation, mean annual temperature, mean annual solar insolation, normalized difference vegetation index (NDVI), human footprint, human population density, and human exploitation). After phylogenetic correction, these variables were used separately and in combination to assess their associations with extinction risk. We found that Chinese lizards with small geographic range, large body size, high habitat specialization, and living in high precipitation areas were vulnerable to extinction. Conservation priority should thus be given to species with the above extinction-prone traits so as to effectively protect Chinese lizards. Preventing future habitat destruction should also be a primary focus of management efforts because species with small range size and high habitat specialization are particularly vulnerable to habitat loss.
... The result of our first analysis, showing moderate evidence for a negative interaction between population abundance and body size in determining time to extinction (Figure 1), indicates that largerbodied organisms have a tendency to collapse to extinction more slowly. Although it is increasingly acknowledged that the level of extinction risk (e.g., IUCN Red List category) is an emergent property of the interaction between biological traits and the type of threatening process (Davidson et al., 2009;Isaac & Cowlishaw, 2004;Owens & Bennett, 2000;Price & Gittleman, 2007;Ripple et al., 2017), this result may seem at odds with the frequently reported positive association between body size and extinction risk (Dirzo et al., 2014;Gaston & Blackburn, 1995;. However, we argue that this can be explained by allometric-related differences in life history and resilience across species. ...
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• Mutual reinforcement between abiotic and biotic factors can drive small populations into a catastrophic downward spiral to extinction—a process known as the “extinction vortex.” However, empirical studies investigating extinction dynamics in relation to species' traits have been lacking. • We assembled a database of 35 vertebrate populations monitored to extirpation over a period of at least ten years, represented by 32 different species, including 25 birds, five mammals, and two reptiles. We supplemented these population time series with species-specific mean adult body size to investigate whether this key intrinsic trait affects the dynamics of populations declining toward extinction. • We performed three analyses to quantify the effects of adult body size on three characteristics of population dynamics: time to extinction, population growth rate, and residual variability in population growth rate. • Our results provide support for the existence of extinction vortex dynamics in extirpated populations. We show that populations typically decline nonlinearly to extinction, while both the rate of population decline and variability in population growth rate increase as extinction is approached. Our results also suggest that smaller-bodied species are particularly prone to the extinction vortex, with larger increases in rates of population decline and population growth rate variability when compared to larger-bodied species. • Our results reaffirm and extend our understanding of extinction dynamics in real-life extirpated populations. In particular, we suggest that smaller-bodied species may be at greater risk of rapid collapse to extinction than larger-bodied species, and thus, management of smaller-bodied species should focus on maintaining higher population abundances as a priority.
... variables were excluded from analyses to avoid multicollinearity (Table S2). We further tested the significance of the possible combinations of important predictors (the marginally significant variables with p < .1 found in the previous step) in promoting extinction vulnerability (Table S3; Chen, Zeng et al., 2019; Price & Gittleman, 2007). The Akaike information criterion corrected for small sample size (AIC c ) was used for model selection, with models differing by less than 2 AIC units considered equivalent. ...
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Aim: China is among the countries with highest mammal diversity in the world, but a considerable proportion of Chinese terrestrial mammal species is currently at risk of extinction. For effective conservation, it would be fundamental to answer the following questions: 1) Is extinction risk randomly distributed among families in Chinese terrestrial mammals? 2) If not, which families are more threatened than expected by chance? 3) What are the major ecological predictors of extinction vulnerability? 4) Does taxonomic difference exist in ecological correlates of extinction risk? (5) To what extent does anthropogenic disturbance contribute to variations in extinction risk? Location: China. Methods: We collected data on biological traits, environmental factors and anthropogenic disturbance for 453 Chinese terrestrial mammals. We used phylogenetically controlled regression models and model selection to identify predictors of extinction risk for the whole species set and for the three large taxonomic groups (Carnivora, Artiodactyla and Lagomorpha) separately. Results: We found that extinction risk was not randomly distributed among families. Seven families (old world monkeys, gibbons, cats, civets and genets, musk deer, deer and bovids) contained significantly higher proportions of threatened species than expected by chance. Geographic range size was the only factor consistently supported in all the best models for the whole species set and for three large taxonomic groups. Although considered important in the global model for the whole species set, body weight was a poor predictor of extinction risk in taxon-specific analyses. We also detected considerable differences in ecological correlates of extinction risk among Carnivora, Artiodactyla and Lagomorpha. After controlling for phylogeny, anthropogenic disturbance was not significantly correlated with extinction risk. Main conclusions: For effective conservation, we should pay special attention to those highly threatened families and the species with limited range size. Our results also highlight the importance of performing taxon-specific analyses for conservation practice.
... This was true for all groups (Table 2), suggesting a similar trend across the vertebrate phylum. Though it is acknowledged that extinction risk is an emergent property of the interaction between biological traits and the type of threatening process (Owens & Bennett 2000;Isaac & Cowlishaw 2004;Price & Gittleman 2007;Brook et al. 2008;Davidson et al. 2009;Ripple et al. 2017), our findings may seem at odds with the frequently reported positive association between body size and extinction threat level (e.g. IUCN threat status) (Gaston & Blackburn 1995;Bennett & Owens 1997;Cardillo et al. 2005;Liow et al. 2008;Dirzo et al. 2014). ...
Most of multi-use species are declining in the wide habitat in spite of the variety of the conservation recommendations formulated by researchers. This may be due to the fact that a large part of researches focused on their socioeconomic importance than the conservation of those species. Pentadesma butyracea is a multi-uses tree species that occurs from Sierra Leone to Gabon in dense Guineo-Congo rainforest and in gallery forests in the Dahomey-Gap of the dry corridor. This work used 56 studies to synthetize the importance of Pentadesma butyracea, enumerate the main threats to species persistence and test if probability of suggesting conservation strategies varied according to main fields of research, the conservation focus and the statement of conservation aim in the study. Our synthesis showed that although 68.75% asked conservation questions, only 43.75% suggested strategies for conservation of Pentadesma butyracea species and/or its habitat, gallery forests. We found 11 combinations of disturbances and 3 isolated disturbances which can simultaneously occur in the wild. We recommended for Pentadesma butyracea and it habitat effective conservation to limit gallery forest width reduction and fragmentation, to enforce the law regarding the minimum distance between farmer field and the gallery forest. Studies on multi-uses trees species must explicitly involve the viability of remnant populations and set the threshold viable habitat size. We also recommend to disentangle drivers of Pentadesma butyracea populations decline using update and accurate mathematical and statistical tools.
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Wildlife management in tropical areas inhabited by rural people requires an understanding of the interactions between game choice of hunters and the biology of game species. This paper presents an analysis that combines information on game use and game biology in an attempt to understand better the game hunting system and its effect on mammalian populations. Game choice by non-tribal inhabitants was studied in the north-eastern Peruvian Amazon within the Reserva Communal Tamshiyacu-Tahuayo (RCTT). The correlation between game preferences and actual harvests was calculated using Ivlev's index of selectivity. Hunters preferred large-bodied mammals and mammals with high economic value. Actual harvests did not reflect preferences of hunters, but were correlated with reproductive productivity of game species, measured as the species $r_{\max}$. Impact of hunting on the biomass of game was not correlated with preferences of hunters or actual harvests. Both game choice by hunters and susceptibility of species to hunting depended mainly on the reproductive productivities of game species. Thus, game management in the RCTT must consider the dominating effects of reproductive biology and consider variance in $r_{\max}$ when determining harvests.
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Tropical moist forests in Africa are concentrated in the Congo Basin. A variety of animals in these forests, in particular mammals, are hunted for their meat, termed bushmeat. This paper investigates current and future trends of bushmeat protein, and non-bushmeat protein supply, for inhabitants of the main Congo Basin countries. Since most bushmeat is derived from forest mammals, published extraction (E) and production (P) estimates of mammal populations were used to calculate the per person protein supplied by these. Current bushmeat protein supply may range from 30 g person1 in the Democratic Republic of Congo, to 180 g person1 in Gabon. Future bushmeat protein supplies were predicted for the next 50 years by employing current E:P ratios, and controlling for known deforestation and population growth rates. At current exploitation rates, bushmeat protein supply would drop 81% in all countries in less than 50 years; only three countries would be able to maintain a protein supply above the recommended daily requirement of 52 g person1. However, if bushmeat harvests were reduced to a sustainable level, all countries except Gabon would be dramatically affected by the loss of wild protein supply. The dependence on bushmeat protein is emphasized by the fact that four out of the five countries studied do not produce sufficient amounts of non-bushmeat protein to feed their populations. These findings imply that a significant number of forest mammals could become extinct relatively soon, and that protein malnutrition is likely to increase dramatically if food security in the region is not promptly resolved.
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Species inhabiting tropical forests are thought to be on the verge of mass extinction. Much work has focused on extinction rates caused by deforestation; however, many of the recorded extinctions that have occurred since 1600 were a result of overhunting. We collected data on the relative abundance of large-bodied mammals in the northeastern Peruvian Amazon in areas with persistent hunting pressure and in areas with infrequent hunting pressure. We quantified the effects of hunting by calculating the change in abundance of species between the infrequently and persistently hunted sites. We report that in Amazonian mammals weighing more than 1 kg the degree of population declines caused by hunting is correlated with the species’ intrinsic rate of natural increase (rmax ), longevity, and generation time. Our results show that species with long-lived individuals, low rates of increase, and long generation times are more vulnerable to extinction than species with short-lived individuals, high rates of increase, and shorter generations.
The phylogenetic comparative approach is a statistical method for analyzing correlations between traits across species. Whilst it has revolutionized evolutionary biology, can it work for conservation biology? Although it is correlative, advocates of the comparative method hope that it will reveal general mechanisms in conservation, provide shortcuts for prioritizing conservation research, and enable us to predict which species will experience (or create) problems in the future. Here, we ask whether these stated management goals are being achieved. We conclude that comparative methods are stimulating research into the ecological mechanisms underlying conservation, and are providing information for preemptive screening of problem species. But comparative analyses of extinction risk to date have tended to be too broad in scope to provide shortcuts to conserving particular endangered species. Correlates of vulnerability to conservation problems are often taxon, region and threat specific, so models must be narrowly focused to be of maximum practical use.
There is a dire need to predict the vulnerability of tropical forest biotas to habitat fragmentation I tested the efficacy of seven ecological traits (body size Iongeuity, fecundity, trophic level, dietary specialization, natural abundance in rain forest and abundance in the surrounding habitat matrix) for predicting responses of 16 nonflying mammal species to rain forest fragmentation in tropical QueenslaM Australia An ordination analysis revealed that most (84%) of the variation in traits was described by two axes, the first separating rand K-selected species, and the second discriminating rare species with specialized diets from common species with generalized diets.
An analysis of the distribution of the small boreal mammals (excluding bats) on isolated mountaintops in the Great Basin led to the following conclusions: 1. The species-area curve is considerably steeper (z = .43) than the curves usually obtained for insular biotas. 2. There is no correlation between number of species of boreal mammals and variables which are likely to affect the probability of colonization, such as distance between island and mainland, distance between islands, and elevation of intervening passes. Apparently the present rate of immigration of boreal mammals to isolated mountains is effectively zero. 3. Paleontological evidence suggests that the mountains were colonized by a group of species during the Pleistocene when the climatic barriers that currently isolate them were abolished. 4. Subsequent to isolation of the mountains, extinctions have reduced the faunal diversity to present levels. Probability of extinction is inversely related to population size and, therefore, is influenced b...
Extinction coefficients are estimated from the rates of disappearance of bird species from islands severed from the Neotropical mainland at the close of the Pleistocene. These coefficients accurately predict the loss of species from Barro Colorado Island, Panama, over a recent 50-year period. Prescriptions are given for the preservation of six categories of extinction prone species.