Does trophy hunting matter to long-term population trends in African herbivores of different dietary guilds?: Trophy hunting and densities of African herbivores

Abstract

The persistence of large African herbivores in trophy hunting areas is still unclear because of a lack of data from long-term wildlife monitoring outside national parks. We compared population trends over the last 30 years in Hwange National Park, Zimbabwe, and the neighbouring Matetsi Safari Area where large herbivores were harvested at an average yearly rate of 2%. We investigated whether trophy hunting altered densities and the proportion of adult males in several large herbivore species. Large herbivores generally thrived as well, or even better, in the hunting areas than in the national park. The proportion of adult males did not differ between the two zones, except for species with higher harvest rates and proportionally more males harvested. Densities were not lower in the hunting areas than in the national park, except for elephant and impala. Large herbivores generally declined throughout the 30-year period in both zones, particularly selective grazers. This is probably because of their greater sensitivity to variation in rainfall compared with other herbivores. Rainfall indeed declined during the study period with droughts being particularly frequent during the 1990s. Browsers, mixed feeders and non-selective grazers generally declined less in the hunting areas than in the national park, possibly because of lower densities of natural predators and elephants outside the park. Our study highlighted that large herbivores may persist in trophy hunting areas as well as in national parks. When rigorously managed, trophy hunting areas may be relevant conservation areas for large herbivores, particularly under the current global decline of wildlife abundance across Africa.

Full text

FEATURE PAPER
Does trophy hunting matter to long-term population
trends in African herbivores of different dietary guilds?
W.-G. Crosmary1,2,3, S. D. Côté1& H. Fritz2
1 Département de Biologie, Université Laval, Québec, Québec, Canada
2 CNRS-UMR 5558, Laboratoire Biométrie et Biologie Evolutive, Université Claude Bernard Lyon 1, Villeurbanne Cedex, France
3 Integrated Wildlife Management Research Unit, CIRAD-EMVT, Montpellier Cedex 5, France
Keywords
trophy hunting; large herbivores; Zimbabwe;
conservation; protected areas.
Correspondence
William-Georges Crosmary, Département de
Biologie, Université Laval, Pavillon
Alexandre-Vachon, 1045 avenue de la
Médecine, Québec, Québec G1V 0A6,
Canada. Tel: +1 418 656 2131 ext. 8152;
Fax: +1 418 656 2043
Email: william.crosmary.1@ulaval.ca
Editor: Iain Gordon
Associate Editor: Yngvild Vindenes
Received 9 January 2014; accepted 27 May
2014
doi:10.1111/acv.12144
Abstract
The persistence of large African herbivores in trophy hunting areas is still unclear
because of a lack of data from long-term wildlife monitoring outside national parks.
We compared population trends over the last 30 years in Hwange National Park,
Zimbabwe, and the neighbouring Matetsi Safari Area where large herbivores were
harvested at an average yearly rate of 2%. We investigated whether trophy hunting
altered densities and the proportion of adult males in several large herbivore
species. Large herbivores generally thrived as well, or even better, in the hunting
areas than in the national park. The proportion of adult males did not differ
between the two zones, except for species with higher harvest rates and proportion-
ally more males harvested. Densities were not lower in the hunting areas than in the
national park, except for elephant and impala. Large herbivores generally declined
throughout the 30-year period in both zones, particularly selective grazers. This is
probably because of their greater sensitivity to variation in rainfall compared with
other herbivores. Rainfall indeed declined during the study period with droughts
being particularly frequent during the 1990s. Browsers, mixed feeders and non-
selective grazers generally declined less in the hunting areas than in the national
park, possibly because of lower densities of natural predators and elephants outside
the park. Our study highlighted that large herbivores may persist in trophy hunting
areas as well as in national parks. When rigorously managed, trophy hunting areas
may be relevant conservation areas for large herbivores, particularly under the
current global decline of wildlife abundance across Africa.
Introduction
Hunting increases mortality in harvested populations, and
may therefore alter their dynamics (Caughley, 1977). With
inappropriate control, hunting may jeopardize the viability
of harvested populations, and may eventually drive them to
extinction (e.g. poaching: Milner-Gulland, Bennett & the
SCB 2002 Annual Meeting Wild Meat Group, 2003a; high-
hunting quotas: Besnard, Novoa & Gimenez, 2010).
Overhunting threatens more than 30% of endangered
mammal species (Baillie, Hilton-Taylor & Stuart, 2004),
particularly ungulates (Price & Gittleman, 2007). Ungulates
often drive the structure, composition and functioning of
ecosystems (Collins et al., 1998; Côté et al., 2004). They
moreover provide goods and income to human communities
(Milner-Gulland et al., 2003a). Understanding and manag-
ing the effects of hunting on ungulate population dynamics
is therefore crucial to conserving the integrity of terrestrial
ecosystems while considering economic interests (Gordon,
Hester & Festa-Bianchet, 2004).
Trophy hunting, contrary to unregulated hunting such as
poaching, is a legalized hunting mode often used as a con-
servation option (Dickson, Hutton & Adams, 2009).
Trophy hunters are willing to pay large amounts of money
to harvest individuals with large secondary sexual charac-
ters (i.e. horns or antlers; Festa-Bianchet, 2003). This
creates incentives for the conservation of natural habitats
and animal populations (Leader-Williams, Smith &
Walpole, 2001). Horns and antlers are particularly devel-
oped in males (Johnstone, 1974; Cumming, 1989) and
increase as males grow older (Côté, Festa-Bianchet &
Smith, 1998; Coltman et al., 2003). Consequently, trophy
hunting harvests are skewed towards adult males, and their
proportion may therefore decrease in hunted populations
(Laurian et al., 2000). Despite productivity usually being
considered higher in populations with female-biased sex
ratios (Caughley, 1977), it is increasingly acknowledged that
the lack of adult males may alter reproduction, recruitment
rates and eventually population dynamics (reviewed in
Milner, Nilsen & Andreassen, 2007).
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Animal Conservation 18 (2015) 117–130 © 2014 The Zoological Society of London 117

Trophy hunting has been shown to reduce horn size with
time (Coltman et al., 2003; Crosmary et al., 2013).
However, offtakes from trophy hunting supposedly repre-
sent only a small fraction of the male segment in hunted
populations (Cumming, 1989; Caro et al., 1998), so that the
impact on population dynamics appears rather limited in
polygynous ungulates (Mysterud, 2012). In Africa, long-
term monitoring is rare (Caro, 2011), particularly outside
national parks (but see Stoner et al., 2007; Western, Russell
& Cuthill, 2009). Consequently, hunting quotas are fre-
quently set on inappropriate estimates based on historical
or anecdotal observations, and are therefore often
unsustainable (e.g. Elkan, 1994; Grobbelaar & Masulani,
2003). Furthermore, law enforcement, which should ensure
quota compliance and limit overhunting, is financially chal-
lenging and thus often neglected in developing countries
(Price & Gittleman, 2007).
These potential effects of trophy hunting on large herbi-
vore populations have fuelled the long-standing debate
whether trophy hunting may be an effective conservation
option in Africa (e.g. Taylor & Dunstone, 1996). In this
context, we compared population densities and proportions
of adult males of several large African herbivores, between
Matetsi Safari Area (MSA; trophy hunting area) and the
neighbouring Hwange National Park (HNP; hunting-free
area), Zimbabwe, over the past 30 years. We hypothesized
that trophy hunting altered population dynamics of large
herbivores. We tested in particular whether populations of
hunting areas had (1) lower densities; (2) lower proportions
of adult males compared with populations in the national
park. We also tested whether (3) densities and proportions
of adult males decreased in hunting areas throughout the
past three decades in comparison with those in the national
park. In addition, we discuss alternative factors that possi-
bly explain the spatiotemporal trends of large herbivore
densities in our study area (i.e. rainfall and the densities of
natural predators and elephants).
Material and methods
Study area
The study covered parts of MSA and HNP. MSA is a major
hunting complex in Zimbabwe (c. 3000 km2; Cumming,
1989) at the north-western border of HNP (c. 15 000 km2)
(Fig. 1). MSA and HNP are unfenced state-owned lands
administrated by Zimbabwe Parks and Wildlife Manage-
ment Authority (ZPWMA). MSA, however, has been leased
to safari operators for hunting tourism since 1973. Seven
hunting units constitute MSA, with units 1–5 in the south-
ern part and units 6 and 7 in the northern part. Hunting
ceased in unit 7 in 1995. Moreover, vegetation types and
environmental conditions (i.e. rainfall, temperature and soil
characteristics) in units 6 and 7 differ from the five other
units (Ganzin, Crosmary & Fritz, 2008; Peace Parks
Foundation, 2009). We thus focused on units 1–5 (404, 292,
356, 470 and 370 km2, respectively; Fig. 1). In HNP, we
covered the blocks that were adjacent to these five hunting
units (i.e. Robins, c. 1000 km2; Sinamatella, c. 1000 km2;
Fig. 1), because their vegetation types and environmental
conditions are similar to MSA (Tables 1 and 2; Ganzin
et al., 2008; Peace Parks Foundation, 2009). We used 10-day
Normalised Difference Vegetation Index (NDVI) images
(resolution 1.2 ×1.2 km) available from 1986 to 2010
(Crosmary et al., 2013) as a proxy of vegetation pro-
ductivity in the region. NDVI was similar in HNP and MSA
between 1986 and 2010 [HNP, NDVI average ±standard
deviation (sd)=0.48 ±0.09; MSA: 0.45 ±0.07; F1,157 =3.2,
P=0.08]. It generally increased during this period [year,
estimate ±standard error =0.002 ±0.002, F1,157 =14.8,
Figure 1 Northern part of Hwange ecosys-
tem, Zimbabwe. The study area is deline-
ated by the thick black rectangle. National
parks (i.e. hunting-free areas) are in white,
hunting areas (units 1–7) of the Matetsi
Safari Area in light grey and hunting areas of
the Forestry Commission in granite. Private
lands and communal lands are, respec-
tively, coloured in dark grey and in black.
The studied hunting units of Matetsi Safari
Area and blocks of Hwange National Park
are indicated in bold font.
Trophy hunting and densities of African herbivores W.-G. Crosmary, S. D. Côté and H. Fritz
Animal Conservation 18 (2015) 117–130 © 2014 The Zoological Society of London
118

P=0.0002), with no difference between HNP and MSA
(F1,157 =1.3, P=0.2). Finally, as state-owned lands, MSA
and HNP are similarly managed regarding anti-poaching,
surface water provision and controlled fires (ZPWMA,
unpubl. data).
Species
We studied African buffalo Syncerus caffer, Burchell’s zebra
Equus burchelli, elephant Loxodonta africana, giraffe Giraffa
camelopardalis, greater kudu Tragelaphus strepsiceros,
impala Aepyceros melampus, reedbuck Redunca arundinum,
sable antelope Hippotragus niger, warthog Phacochoerus
aethiopicus and waterbuck Kobus ellipsiprymnus. These
species are fairly common large herbivores encountered in
southern Africa (Skinner & Chimimba, 2005) and are
hunted for trophies (Lindsey, Roulet & Romañach, 2007).
They have distinct diets and body weight, but most are
water dependent (except for warthog and giraffe; Table 3).
This allows comparisons that may provide insights on alter-
Table 1 Eco-regions, geology and soil characteristics in the north-western blocks of Hwange National Park (HNP) and the adjacent blocks of
Matetsi Safari Area (MSA), Zimbabwe (adapted from Peace Parks Foundation, 2009)
Site Eco-region Geology Soil types Soil texture Soil drainage
MSA Zambezian and Mopane
woodlands
Basalt Leptosols (shallow, rocky) Sandy Well drained
HNP
(western blocks)
Zambezian and Mopane
woodlands
Basalt Leptosols (shallow, rocky) Sandy Well drained
Siltstone/granite Solonetz (dense, high in
sodium)
Clayey Poorly drained
Table 2 Proportion (mean % ±standard deviation) of the main vegetation structures, woody species and the availability of surface water in the
north-western blocks of Hwange National Park (HNP) and the adjacent blocks of Matetsi Safari Area (MSA), Zimbabwe (from Ganzin et al., 2008)
HNP MSA Mann–Whitney–Wilcoxon test
Vegetation structure
Open woodland
(trees >30 and <50%, shrubs <10%)
32.9 ±26 22.8 ±7.1 W=3, P=1
Dense woodland
(trees >50%, shrubs <10%)
13.4 ±8.9 5.5 ±1.5 W=6, P=0.2
Open shrubland
(shrubs >30 and <50%, trees <10%)
32.1 ±14.5 44.6 ±7.4 W=1, P=0.4
Grassland
(shrubs and trees <10%)
14.2 ±20.1 7.4 ±5.5 W=3, P=1
Shrubland
(shrubs >50%, trees <10%
1.1 ±1.0 1.5 ±2.4 W=4, P=0.8
Tree to shrub
(mixed woodland/shrubland)
3.2 ±0.9 17.8 ±6.5 W=0, P=0.2
Woody species
Colophospermum mopane 68.4 ±27.8 61.1 ±7.0 W=3, P=1
Combretum sps. 6.1 ±1.6 21.1 ±2.1 W=0, P=0.2
Baikiaea plurijuga 5.4 ±7.6 3.8 ±3.9 W=3, P=1
Terminalia sericea 1.7 ±0.1 4.4 ±0.5 W=0, P=0.2
Brachystegia sps. 0.2 ±0.2 0.9 ±0.6 W=1, P=0.4
Burkea africana 0.9 ±1.2 0.9 ±1.2 W=2, P=0.8
Water availabilitya
All waterholes and main rivers 76.5 ±15.8 78.4 ±17.6 W=3, P=1
Pumped waterholes 53.2 ±28. 47.9 ±25.8 W=3, P=1
aExpressed as the proportion of area in each block located within 5 km from potential surface water supply during the dry season.
Table 3 Main large herbivores of Matetsi Safari Area (MSA, hunting
areas) and Hwange National Park (HNP, hunting-free area), classified
by diet and dependency on surface water, and ranked according to
increasing body weight
Species Diet
Surface water
dependency
Mean body
weight (kg)
Warthog Selective grazeraNo 30
Impala Mixed feeder Yes 41
Reedbuck Selective grazer Yes 55
Greater kudu Browser Yes 136
Waterbuck Selective grazer Yes 205
Sable antelope Selective grazer Yes 210
Zebra Non-selective grazer Yes 216
Buffalo Non-selective grazer Yes 495
Giraffe Browser No 700
Elephant Mixed feeder Yes 1725
aWarthogs are less selective than other selective grazers, and may
occasionally browse (Bothma et al., 2004). Adapted from Bothma,
van Rooyen & du Toit (2002).
W.-G. Crosmary, S. D. Côté and H. Fritz Trophy hunting and densities of African herbivores
Animal Conservation 18 (2015) 117–130 © 2014 The Zoological Society of London 119

native factors that could have influenced population density
trends in our study area. For instance, selective grazers are
particularly sensitive to a low rainfall regime (Owen-Smith,
2008), so their densities may be more affected than other
species during dry years. In addition, herbivores with a
smaller body size are more vulnerable to natural predators
than larger prey (Sinclair, Mduma & Brashares, 2003).
Their densities may therefore be more influenced by varia-
tion in natural predator abundances than larger herbivores.
Population trends
Yearly road counts were carried out in late dry season
(September/October) from 1977 to 2010 in the MSA hunting
units and HNP management blocks. Data, however, were
missing between 1987 and 1994 in HNP. We therefore
divided the dataset into two periods (i.e. 1977–1986 and
1995–2010 in both zones). Most available roads were used
as transects following the distance sampling procedure with
two observers, whose effect was accounted for in the analy-
ses (Buckland et al., 2001; Chamaillé-Jammes et al., 2009
for similar procedure in HNP). Penetration of roads was 0.7
and 3.2 km km−2in HNP and MSA, respectively. The dis-
tance travelled was 12 536 km in HNP, and 24 920 km in
MSA. These were very high compared with other studies
in African savannas (e.g. Fischer & Linsenmair, 2001;
Brashares & Sam, 2005; Gaidet-Drapier et al., 2006; Caro,
2011). The two areas were thus well covered by road counts,
so the data collected were representative of the two areas
and comparable between them. For each group of herbi-
vores encountered, species, group size and number of adult
males were recorded.
We analysed data using distance sampling software
(Thomas et al., 2006) and obtained estimates of population
densities per species and per year in each unit/block. Coef-
ficients of variation associated with population estimates
averaged 17% in warthog, 14% in impala, 34% in reedbuck,
16% in greater kudu, 35% in waterbuck, 25% in sable ante-
lope, 20% in zebra, 44% in buffalo, 26% in giraffe and 36%
in elephant. We then computed the proportion of adult
males as the ratio of the total number of adult males
counted over the total number of individuals counted per
species and per year in each unit/block. Because seasonal
migrations in southern Africa are less common than in
eastern Africa (Walker, 1979), and because most large her-
bivores in HNP and MSA are sedentary and do not migrate
(V. Booth, pers. comm.), the risk of dependency of popula-
tion data between the two areas was limited.
Rainfall regime
Fluctuations in the abundance of herbivore populations in
African semi-arid savannas are largely driven by rainfall,
particularly during the dry season (Mduma, Sinclair &
Hilborn, 1999; Ogutu & Owen-Smith, 2003). Although most
rain falls in the wet season, from November to April, some
falls during the dry season. Data on annual and dry season
rainfalls in the study area were available for 1976–2005.
Annual and dry season averages were 544 (Fig. 2a) and
10.2 mm (Fig. 2b), respectively. There was, however, a high
variability associated with average annual and dry season
rainfalls (coefficient of variation, 32 and 142%, respec-
tively). Although the period from 1995 to 2010 experienced
more years below the long-term average than 1977–1986
(i.e. six vs. three), annual rainfall did not significantly differ
between the two periods (average annual rainfall ±sd:
591 ±170 vs. 487 ±198; Mann–Whitney test: W=77,
P=0.3) (Fig. 2a). However, the 3-year running means of
Figure 2 Trends in (a) annual rainfall and (b) dry season rainfall over 30
years in units 1–5 of Matetsi Safari Area (hunting areas), and the
Robins and Sinamatella blocks in Hwange National Park (hunting-free
area), Zimbabwe. Bars indicate annual records and solid lines indicate
the 3-year running means. The horizontal dotted line represents the
long-term average. The vertical dotted lines separate the study
periods (see text for details).
Trophy hunting and densities of African herbivores W.-G. Crosmary, S. D. Côté and H. Fritz
Animal Conservation 18 (2015) 117–130 © 2014 The Zoological Society of London
120

annual rainfall linearly decreased from 1977 to 2010
(Fig. 2a; mean year effect ±se:−6.7 ±1.7, F1,28 =15,
P<0.001). Dry season rainfall did not significantly differ
between the two periods (14 ±16 vs. 13 ±16; Mann–
Whitney test: W=68, P=0.6) (Fig. 2b). However, the
period from 1995 to 2010 followed a dry spell decade (i.e.
1986–1994), with dry season rainfall constantly below the
long-term average (Fig. 2b). Therefore, if annual or dry
season rainfall were of primary influence on herbivore popu-
lation dynamics, population densities should generally be
lower in 1995–2010 than from 1977 to 1986 for most herbi-
vore species, both in MSA and HNP.
Harvest rates
Cumming (1989) reported that annual harvest rates for large
herbivores in MSA were c. 2%. Data on offtakes for the study
period were only available for buffalo, elephant, impala,
greater kudu and sable antelope. Thus, we were only able to
compute harvest rates (i.e. number of harvested animals over
the estimated population size) for these species, and found an
average of 1.7 ±1.2% throughout the study period, similar to
Cumming (1989). This varied among species [analysis of
variance (ANOVA), F4,104 =10.5, P<0.0001], with sable
antelope and elephant experiencing higher average harvest
rates than impala, buffalo and greater kudu (Fig. 3a).
Trophy hunters essentially harvest large-horned animals (i.e.
adult males). Females can nonetheless be on quotas for food
rations and bait for hunting carnivores. On average,
80 ±17% of the animals on quotas were males; this varied
among species (ANOVA, F4,150 =15.7, P<0.0001), being
higher for sable antelope and elephant and lower for impala
(Fig. 3b). If trophy hunting alters population dynamics and
structure, then density and proportion of adult males should
be especially low in hunting areas compared with the national
park for species like sable antelope and elephant.
Analyses
To test whether population densities and the proportion of
adult males differed between hunting areas and the national
park, we performed ANOVAs with zone (i.e. MSA vs.
HNP) and period (i.e. 1977–1986 vs. 1995–2010) as factors.
We also tested the interaction between zone and period
because we expected differences between hunting areas and
the national park to increase through time. Because tempo-
ral serial autocorrelation may affect time series counts, we
controlled for temporal autocorrelation using a first-order
autoregressive covariance structure (Pinheiro & Bates,
2000). Densities were square root transformed and propor-
tions of adult males were log transformed to meet normality
assumptions. We used units/blocks as random effects in the
ANOVAs using the R nlme package (http://www.r-project
.org/).
We then built a tree-based model to test whether there
were groups of species whose densities had been similarly
affected by zone and period (Breiman et al., 1984). For trends
in densities to be compared among species, we first normal-
ized densities for each species before pooling them in a single
dataset, with zone, period and species as factors. We then
used the R rpart and partykit packages (http://www
.r-project.org/) to build a classification tree of the normalized
densities according to these three factors, and then simplified
it using the pruning method (Breiman et al., 1984).
Figure 3 Observed values of (a) harvest rate (number of harvested
animals over the estimated population size) and (b) proportion of
males in hunting quotas between 1978 and 2008 in hunting units 1–5
of Matetsi Safari Area, Zimbabwe, for buffalo, elephant, impala,
greater kudu and sable antelope. The horizontal line within the box
represents the median, the box illustrates the range between the
25th and 75th percentiles, the two dotted segments outside the box
represent the 10th and 90th percentiles, and the black dots are the
observation <10th or >90th percentiles. Different letters indicate
significant differences at P<0.05.
W.-G. Crosmary, S. D. Côté and H. Fritz Trophy hunting and densities of African herbivores
Animal Conservation 18 (2015) 117–130 © 2014 The Zoological Society of London 121

Results
Population densities
Throughout the study period, population densities did not
differ between MSA and HNP for buffalo, giraffe, greater
kudu, reedbuck, warthog and zebra, whereas they were sig-
nificantly higher in MSA than in HNP for sable antelope
and waterbuck (Table 4; Fig. 4). Densities were significantly
lower in MSA than in HNP for elephant and impala
(Table 4; Fig. 4).
Densities generally declined between 1977–1986 and
1995–2010 in both zones for selective grazers (Table 4;
Fig. 5). In HNP, this decline was c. 94, 73, 50 and 90% for
reedbuck, sable antelope, warthog and waterbuck, respec-
tively. The decline was milder in MSA (i.e. c. 80, 62, 31 and
56%, respectively, for the same species; Fig. 5), although the
differences were not statistically significant (Table 4). Sable
antelope densities remained higher in MSA compared with
HNP throughout the study period (Table 4; Fig. 4). Densi-
ties of giraffe, impala and greater kudu were higher in HNP
than in MSA from 1977 to 1986 (Table 4; Fig. 4). However,
they declined between 1977–1986 and 1995–2010 in HNP
(about 60, 48 and 52%), whereas they increased in MSA
(about 49, 32 and 61%)(Table 4; Fig. 5); densities did not
differ between zones from 1995 to 2010. Buffalo tended to
experience similar trends as giraffe, impala and greater kudu
(Fig. 4), although not significantly (Table 4). For zebra, we
observed no significant temporal trend in densities and no
significant difference between MSA and HNP (Table 4;
Figs 4 and 5). In elephant, densities were generally c. 98%
higher from 1995 to 2010 compared with 1977–1986. Den-
sities were higher and seemed to increase more in HNP
compared with MSA, but not significantly (Table 4; Figs 4
and 5).
The selected classification tree indicated that period was
the factor explaining most variation in normalized densities
among studied species, with densities being generally lower
in 1995–2010 than in 1977–1986 (Fig. 6). Trends for selec-
tive grazers (i.e. reedbuck, sable antelope, warthog and
waterbuck) differed from trends of browsers, mixed feeders
and non-selective grazers (i.e. giraffe, greater kudu,
elephant, impala, buffalo and zebra). For selective grazers,
overall densities did not differ between MSA and HNP,
and both zones experienced a decrease in densities of
similar magnitude between 1977–1986 and 1995–2010. For
browsers, mixed feeders and non-selective grazers, densities
were generally lower in MSA than HNP from 1977 to 1986,
particularly for buffalo, giraffe, impala and greater kudu
(Fig. 6). However, this difference in densities between MSA
and HNP disappeared in 1995–2010 (Fig. 6), which indi-
cated a greater decrease of densities in HNP compared with
MSA for these species (Fig. 6). Elephant and zebra were a
distinct subgroup within the group of browsers, mixed
feeders and non-selective grazers, because their density
trends differed from those of the rest of the group (Fig. 6).
This was consistent with the results from the ANOVAs
because elephant were the only species whose density
increased during the study period, and zebra did not
show any significant spatial pattern or temporal trend of
densities.
Proportion of adult males
For sable antelope and elephant, the proportion of adult
males was significantly lower in MSA than in HNP, declin-
ing in MSA but not in HNP between the two periods
(Table 5; Fig. 7). For waterbuck and zebra, this proportion
declined between the two periods, and tended to be lower
in MSA than HNP (Table 5; Fig. 7). We found no signifi-
cant effect of zone, period or their interaction on the pro-
portion of adult males for the other species (Table 5), but
this proportion seemed to be lower in MSA than in HNP
for most of them, more particularly from 1995 to 2010
(Fig. 7).
Table 4 Two-way analysis of variance of densities (square root
transformed) of African ungulate species according to period
(1977–1986 vs. 1995–2010), zone (hunting-free area vs. hunting
areas), and their interaction in Hwange National Park and the adjacent
Matetsi Safari Area, Zimbabwe
Species Factor d.f.
Densities
r.d.f. FP
Buffalo Period 1 88 0.3 0.6
Zone 1 5 2.8 0.2
Period ×zone 1 88 0.6 0.4
Elephant Period 1 88 18.1 0.0001
Zone 1 5 11.2 0.02
Period ×zone 1 88 2.6 0.1
Giraffe Period 1 88 1.2 0.3
Zone 1 5 4.1 0.1
Period ×zone 1 88 26.4 0.0001
Impala Period 1 87 3.0 0.1
Zone 1 5 12.5 0.02
Period ×zone 1 87 25.6 <0.0001
Greater kudu Period 1 88 1.2 0.3
Zone 1 5 12.5 0.6
Period ×zone 1 88 25.6 <0.0001
Reedbuck Period 1 88 31.5 <0.0001
Zone 1 5 1.1 0.4
Period ×zone 1 88 3.6 0.06
Sable antelope Period 1 88 73.9 <0.0001
Zone 1 5 21.4 0.006
Period ×zone 1 88 1.1 0.3
Warthog Period 1 88 16.6 0.0001
Zone 1 5 1.3 0.3
Period ×zone 1 88 2.0 0.2
Waterbuck Period 1 88 95.2 <0.0001
Zone 1 5 11.7 0.001
Period ×zone 1 88 1.3 0.3
Zebra Period 1 88 0.3 0.6
Zone 1 5 1.6 0.3
Period ×zone 1 88 2.8 0.1
d.f., degrees of freedom; r.d.f, residual degrees of freedom.
Trophy hunting and densities of African herbivores W.-G. Crosmary, S. D. Côté and H. Fritz
Animal Conservation 18 (2015) 117–130 © 2014 The Zoological Society of London
122

Figure 4 Population densities in Matetsi Safari Area (Hunting Areas, HA, grey) versus Hwange National Park (hunting-free area, non-HA, white),
Zimbabwe, from 1977 to 1986 and 1995 to 2010. The bars indicate the average values and their associated standard deviation. Different letters
indicate statistically significant difference at P<0.05.
W.-G. Crosmary, S. D. Côté and H. Fritz Trophy hunting and densities of African herbivores
Animal Conservation 18 (2015) 117–130 © 2014 The Zoological Society of London 123

Discussion
Populations of large herbivores are generally declining in
African-protected areas (reviewed in Caro & Scholte, 2007;
Craigie et al., 2010). This decline raises concerns about the
efficiency of protected areas as a conservation tool
(Newmark, 2008), and suggests there is potential in alterna-
tive conservation zones such as trophy hunting areas
(Lindsey et al., 2007). Because long-term monitoring of
wildlife outside national parks is rare (Caro, 2011), we lack
empirical data to investigate the long-term effects of trophy
hunting on population structure and density. This lack of
data seriously limits our capacity to evaluate the conserva-
tion potential of trophy hunting areas. We provide here a
rare analysis of long-term impacts of trophy hunting on
densities and proportions of adult males of several large
herbivore populations.
Trophy hunting
Overall, trophy hunting had a marginal effect on the tem-
poral trends of the structure and density of large herbivore
Figure 5 Relative change of mean population densities between
1977–1986 and 1995–2010 for ungulate species in Hwange National
Park (hunting-free area, non-HA, white) versus Matetsi Safari Area
(Hunting Areas, HA, grey), Zimbabwe. The ungulate species are
grouped by dietary guild (browsers, mixed feeders, grazers and
selective grazers) and separated by dashed lines.
Figure 6 Classification tree of the normalized densities according to
the zone (national park vs. hunting areas), period (1977–1986 vs.
1995–2010) and species (buffalo, Burchell’s zebra, elephant, giraffe,
greater kudu, impala, reedbuck, sable antelope, warthog and water-
buck), Zimbabwe. Circles are the nodes of the tree. The number of
observations (n) and the mean value of normalized densities are
indicated at the end of each branch.
Table 5 Two-way analysis of variance of proportion of adult males
(log transformed) of African ungulate species according to period
(1977–1986 vs. 1995–2010), zone (hunting-free area vs. hunting
areas) and their interaction, in Hwange National Park and the adjacent
Matetsi Safari Area, Zimbabwe
Species Factor d.f.
Adult male %
r.d.f. FP
Elephant Period 1 72 0.1 0.8
Zone 1 5 7.1 0.04
Period ×zone 1 72 5.4 0.02
Giraffe Period 1 84 2.8 0.1
Zone 1 5 4.1 0.1
Period ×zone 1 84 0.4 0.5
Impala Period 1 89 2.5 0.1
Zone 1 5 2.4 0.2
Period ×zone 1 89 2.9 0.1
Greater kudu Period 1 89 2.4 0.1
Zone 1 5 0.6 0.5
Period ×zone 1 89 0.2 0.7
Reedbuck Period 1 59 0.9 0.3
Zone 1 5 0.0 1.0
Period ×zone 1 59 0.3 0.6
Sable antelope Period 1 73 2.0 0.2
Zone 1 5 9.1 0.03
Period ×zone 1 73 6.9 0.01
Warthog Period 1 88 0.2 0.6
Zone 1 5 0.8 0.4
Period ×zone 1 88 0.6 0.4
Waterbuck Period 1 81 5.3 0.02
Zone 1 5 5.8 0.06
Period ×zone 1 81 0.3 0.6
Zebra Period 1 86 3.8 0.0002
Zone 1 5 14.5 0.06
Period ×zone 1 86 2.7 0.1
Buffalo groups were too large to identify individuals.
d.f., degrees of freedom; r.d.f., residual degrees of freedom.
Trophy hunting and densities of African herbivores W.-G. Crosmary, S. D. Côté and H. Fritz
Animal Conservation 18 (2015) 117–130 © 2014 The Zoological Society of London
124

populations in the study area. Only elephant and impala
showed lower densities in MSA than HNP throughout the
study period. Conversely, densities of sable antelope were
higher in the hunting areas than in the national park. Under
the hypothesis of a detrimental effect of trophy hunting on
population densities, we would have expected opposite
results because harvest rates were higher for sable antelope
than for other species. Harvest rates, however, were gener-
ally low in MSA, c. 2% per year (this study; Cumming,
1989). It is likely that at this level of harvest, the impact of
trophy hunting on population densities was minimal. For
instance, Caro et al. (1998) found few significant differences
in mammal densities between hunting areas and national
parks in Tanzania, and suggested that harvest rates below
10% per year were unlikely to impact population sizes.
Examples in other ecosystems revealed no impact of trophy
hunting on ungulate dynamics (Milner et al., 2007;
Mysterud, 2012; but see Palazy et al., 2012). Surprisingly,
for some species (i.e. giraffe, impala, greater kudu), densities
declined from 1977 to 1986 and 1995 to 2010 in HNP,
whereas they did not change or increased in MSA. For
species whose densities declined in MSA (i.e. reedbuck,
sable antelope, warthog and waterbuck), there was a decline
of similar magnitude in HNP. This suggests a limited effect
from trophy hunting and that other factors were responsible
for this general decline (see below).
We expected lower proportions of adult males in hunting
areas than in HNP because trophy hunting is male biased
(this study; Festa-Bianchet, 2003). For sable antelope and
elephant, harvest rates and proportions of males on quotas
were higher than for other species. This probably explains
why, for these two species in particular, the proportion of
adult males was significantly lower in MSA than in HNP,
and declined in MSA but not in HNP. For the other species,
we observed the same trend overall, although not signifi-
cantly. This trend may be due to the high variance associ-
ated with the proportion of adult males. Decreased male
proportions have been documented in many other ungulates
Figure 7 Proportion of adult males in
Matetsi Safari Area (Hunting Areas, HA,
grey) versus Hwange National park
(hunting-free area, non-HA, white), Zimba-
bwe, between 1977–1986 and 1995–2010.
Bars indicate the average values and
segment their associated standard devia-
tion. Different letters indicate statistically
significant differences at P<0.05.
W.-G. Crosmary, S. D. Côté and H. Fritz Trophy hunting and densities of African herbivores
Animal Conservation 18 (2015) 117–130 © 2014 The Zoological Society of London 125

hunted for trophies worldwide (e.g. Langvatn & Loison,
1999; Garel et al., 2006; Holand et al., 2006). However, only
rare examples reported reproductive collapse due to extreme
lack of males (e.g. Milner-Gulland et al., 2003b). Alterna-
tively, the removal of only a few experienced adult males
may be sufficient to jeopardize population growth or main-
tenance through the alteration of reproductive phenology
(Noyes et al., 1996; Singer & Zeigenfuss, 2002). However,
we doubt that it occurred in our study areas; despite the
proportion of adult males tending to be lower and to decline
in the hunting areas compared with the national park, the
same pattern was not observed in population densities.
Poaching
With the economic decline and political instability that Zim-
babwe has been facing since 2000, there is concern about
poaching increasing inside and around protected areas (but
see Gandiwa et al., 2013). Around HNP, land use changed
and human encroachment increased, particularly on the
eastern side, which has triggered poaching there in the
recent years (Animal Life Line for Anti-poaching, unpubl.
data). The Robins and Sinamatella blocks are far from set-
tlements and are therefore less exposed to poaching. His-
torically, there was no significant poaching for bushmeat in
MSA or in Robins and Sinamatella (V. Booth, pers.
comm.). Any poaching or evidence of snaring was quickly
resolved either by ZPWMA patrols or by the safari opera-
tors. Therefore, it is unlikely that differences in poaching
intensity could have been responsible for the lower herbi-
vore densities and for their faster decline in the park.
Rainfall
The general decline of population densities between 1977–
1986 and 1995–2010 observed in most species across the
study area indicated that factors other than trophy hunting
were involved. In African savannas, rainfall is a proxy of
primary productivity that may determine population
numbers of large herbivores (Fritz & Duncan, 1994) and
annual changes of densities (Mduma et al., 1999). Annual
rainfall declined over the last 30 years in the study area. In
particular, the period from 1995 to 2010 followed an
unprecedented dry spell (i.e. 1986–1994; Fig. 2;
Chamaillé-Jammes, Fritz & Murindagomo, 2006), during
which dry season rainfall was constantly below the long-
term average. Droughts may be particularly detrimental for
large African herbivore populations (e.g. Ottichilo, de
Leeuw & Prins, 2001; Dunham, Robertson & Grant, 2004).
Interestingly, population decline was more pronounced for
selective grazers (i.e. reedbuck, sable antelope, warthog,
waterbuck) than for non-selective grazers (i.e. buffalo,
zebra), mixed feeders (i.e. elephant, impala) and browsers
(i.e. giraffe, greater kudu). This is in accordance with a
scenario proposing rainfall as a primary factor determining
temporal trends of large herbivore densities in our study
area. Browse production is more constant over time than
grass production (Rutherford, 1984), making browsers and
mixed feeders potentially more resistant to droughts than
grazers (Hillman & Hillman, 1977; Owen-Smith, 2008), and
selective grazers in particular (e.g. Murray & Brown, 1993).
Indeed, most examples of large herbivore declines related to
droughts in Africa involve grazers (e.g. Mduma, Hilborn &
Sinclair, 1998; Harrington et al., 1999). Among the selective
grazers, warthog experienced a twofold milder decline than
reedbuck, sable antelope and waterbuck. This is not surpris-
ing because warthog can sometimes feed on browse and
forbs (Bothma, van Rooyen & van Rooyen, 2004), and
because their high reproductive rate may enable their popu-
lation to recover quickly from droughts. Given the actual
recurrence of long and severe dry episodes in southern
Africa (Hulme et al., 2001; Nicholson, 2001), selective
grazers may deserve particular conservation focus in
hunting areas because they may be less able to cope with
additional sources of mortality compared with non-selective
grazers, browsers and mixed feeders.
Natural predation
During the study period, population densities of large her-
bivores generally declined more in HNP than in MSA.
Trophy hunting and rainfall alone are not sufficient to
explain this result, and we suspect that natural predation
may have played a role. Indeed, predators can negatively
impact large herbivore populations (Schmitz, Hambäck &
Beckerman, 2000; Sinclair et al., 2003; Ripple & Beschta,
2004). Between 1971 and the early 1990s, lion Panthera leo,
leopard P. pardus and spotted hyaena Crocuta crocuta
numbers doubled in HNP (Wilson, 1997), but declined
afterwards (Drouet-Hoguet, 2007; Loveridge et al., 2007a).
Equivalent information does not exist for MSA. However,
during this period, large carnivore hunting occurred in MSA
at a rate of c. 8% per year (Cumming, 1989). The removal of
adult males in lion and leopard populations is particularly
detrimental for recruitment and population dynamics
(Loveridge et al., 2007a; Packer et al., 2011). Moreover,
densities of large African carnivores are generally lower
outside national parks than inside (e.g. Caro, 1999;
Wallgren et al., 2009). Therefore, we can assume that den-
sities of lion and leopard remained lower in MSA than in
HNP, at least until the mid-1990s. This could be why large
herbivore densities generally declined more in HNP than in
MSA between 1977–1986 and 1995–2010. Additionally,
impala and greater kudu are major prey species for most
large African carnivores in the region (Drouet-Hoguet,
2007; Loveridge et al., 2007b; Rasmussen, 2009), which may
explain why these species’ densities decreased in HNP while
remaining constant or increasing in MSA. The same argu-
ment may be formulated for giraffes, which are common
lion prey in Hwange (Loveridge et al., 2007b). The pattern
tended to be the same, although not significantly so, for
buffalo and zebra, two other major lion prey species in
Hwange (Loveridge et al., 2007b). Conversely, for selective
grazers, the difference in temporal density trends between
HNP and MSA was less stark, possibly because rainfall was
Trophy hunting and densities of African herbivores W.-G. Crosmary, S. D. Côté and H. Fritz
Animal Conservation 18 (2015) 117–130 © 2014 The Zoological Society of London
126

the primary driver for these species (e.g. Mduma et al.,
1999).
Elephant
The African bush elephant was the only large herbivore
species whose densities increased in both zones during the
study period. Chamaillé-Jammes et al. (2008) previously
showed that elephant numbers in HNP drastically increased
from 15 000 to 35 000 since the cessation of culling in 1986.
Elephant densities increased in both zones, but remained
higher in HNP compared with MSA throughout the study
period. This is coherent with elephant behaviour, because
elephants tend to avoid human-disturbed areas (van Aarde,
Whyte & Pimm, 1999; Caro, 1999). High elephant densities
are suspected to be detrimental for other large herbivores,
because of habitat modification and competition for food
and surface water (Cumming, 1982; Fritz et al., 2002;
Parker, Bernard & Adendorff, 2009; Castelda et al., 2011),
but this is still widely debated (Skarpe et al., 2004;
Guldemond & van Aarde, 2008; Valeix et al., 2009). Further
investigation is required to conclude whether temporal
trends and spatial patterns of elephant densities could be
partly responsible for the greater decline of large herbivore
densities in HNP compared with the neighbouring MSA
during the study period.
Conclusion
Our study illustrates that when removal is rather conserva-
tive and rigorously managed, trophy hunting areas may
be valuable conservation zones for large herbivores.
However, natural factors may obscure the effect of trophy
hunting on spatial and temporal trends of herbivore densi-
ties. For instance, hunting areas might act as refuges for
some large herbivores from high densities of predators and
dominant competitive species. This remains to be investi-
gated in our study area. Finally, herbivore dietary guilds
should be considered in the management of hunting
areas, because diet requirements can influence herbivore
responses to additional sources of mortality such as trophy
hunting.
There are other examples of high densities of large herbi-
vores in hunting areas of Zimbabwe (Lindsey, Romañach &
Davies-Mostert, 2009) and of Africa (Lindsey et al., 2007).
However, the results of these studies should not be general-
ized. Where hunting is poorly managed, where land tenure
authorizes human settlement or where local human popula-
tions do not benefit from hunting, hunting areas are less
likely to host high densities of large herbivores (e.g. Caro,
1999; Dunham, 2002; Setsaas et al., 2007). Whereas ungu-
late populations may persist in trophy hunting areas as well
as in national parks, this is usually not the case for large
carnivores. In addition, trophy hunting may come with
undesirable evolutionary changes that may weaken har-
vested populations (Coltman et al., 2003). These considera-
tions demand caution when considering the potential of
wildlife conservation in trophy hunting areas.
Acknowledgements
We acknowledge the Director General of the Zimbabwe
Parks and Wildlife Management Authority for providing
the opportunity to carry out this research and for
permission to publish this manuscript. W.-G.C. was sup-
ported by scholarships from the French Agence Nationale
de Recherche, the BioFun project ANR-05-BDIV-013-01,
the Natural Sciences and Engineering Research Council of
Canada Discovery grant of SDC and the Soutien aux
cotutelles internationales de thèses de l’Université Claude
Bernard Lyon 1. This research was carried out within
the framework of the HERD project (Hwange Environ-
mental Research Development), as well as with the
Research Platform Production and Conservation in Part-
nership (RP-PCP), funded by the French Ministère des
Affaires Etrangères, Ambassade de France au Zimbabwe,
CIRAD, CNRS and the IFB Global Change and Biodi-
versity. We thank S. Le Bel, CIRAD representative in
Zimbabwe. We are indebted to T. Tarakini, P. Makumbe,
T.-T. Maponga, G. Ncube, B. Eliotout, H. Valls and
S. Périquet who completed data entry of the road count
folders. We are grateful to G. Daigle for statistical
assistance.
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