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Abstract

Advances in the understanding of ecological factors determining predator–prey interactions have provided a strong theoretical background on diet preferences of predators. We examined patterns of jaguar predation on caiman in southern Pantanal, Brazil. We investigated factors affecting predation rates and vulnerability of caiman to predation by jaguars. We recorded 114 caiman mortality incidents. Predation accounted for 62.3% (n = 71) of all caiman found dead, while other causes of mortality (nonpredation) accounted for 37.7% (n = 43). We found that jaguars prey on a broad size range of caiman body and caiman predation was influenced by distance to forests. During dry seasons, 70% (n = 49) of deaths were due to predation, while 30% (n = 21) were due to nonpredation causes. However, we found no significant relationship between annual and monthly killings of caiman and rainfall totals by year and month (r = 0.130, r = -0.316). The annual flooding regime may be a more important factor influencing prey selection by jaguars. Although neotropical crocodilians are relatively well studied, their interactions with jaguars have been mostly ignored and should be prioritized in future studies.
Predator–prey interactions: jaguar predation on caiman in a
floodplain forest
F. C. C. Azevedo1,2 & L. M. Verdade3
1 Departamento de Ciências Naturais, Universidade Federal de São João del Rei, São João del Rei, Brazil
2 Instituto Pró-Carnívoros, Atibaia, Brazil
3 Laboratório de Ecologia Isotópica/USP, Piracicaba, SP, Brazil
Keywords
caiman; jaguar; Pantanal; predator–prey
interaction; temporal variation.
Correspondence
Fernando C. C. Azevedo, Departamento de
Ciências Naturais, Universidade Federal de
São João del Rei, Praça Dom Helvécio 74
Bairro Fábricas, São João del Rei, MG
36301-160, Brazil. Tel: +55 3233792483
Email: fazevedo@ufsj.edu.br
Editor: Anne Braae
Received 7 February 2011; revised 9 August
2011; accepted 2 September 2011
doi:10.1111/j.1469-7998.2011.00867.x
Abstract
Advances in the understanding of ecological factors determining predator–prey
interactions have provided a strong theoretical background on diet preferences of
predators. We examined patterns of jaguar predation on caiman in southern
Pantanal, Brazil. We investigated factors affecting predation rates and vulnerabil-
ity of caiman to predation by jaguars. We recorded 114 caiman mortality inci-
dents. Predation accounted for 62.3% (n=71) of all caiman found dead, while
other causes of mortality (nonpredation) accounted for 37.7% (n=43). We found
that jaguars prey on a broad size range of caiman body and caiman predation was
influenced by distance to forests. During dry seasons, 70% (n=49) of deaths were
due to predation, while 30% (n=21) were due to nonpredation causes. However,
we found no significant relationship between annual and monthly killings of
caiman and rainfall totals by year and month (r=0.130, r=-0.316). The annual
flooding regime may be a more important factor influencing prey selection by
jaguars. Although neotropical crocodilians are relatively well studied, their inter-
actions with jaguars have been mostly ignored and should be prioritized in future
studies.
Introduction
Diet selection is a vital concept for understanding predator–
prey interactions and the relative impact of predators on dif-
ferent prey. In this context, the complex interaction between
predator and prey has long been addressed by the optimal
foraging theory (OFT) (MacArthur & Pianka, 1966). OFT
predicts that in a productive environment, predators should
be selective towards more profitable prey. However, prey
behavior can have important effects on active predator’s
choice (Abrams & Matsuda, 1993). For instance, an ambush
predator facing two alternative mobile prey species with dif-
ferences in behavior would prefer the type that is more active
if conditions of abundance, capturing and handling are similar
(Persson & Greenberg, 1990).
Diet selection by large terrestrial carnivores can be affected
by several ecological factors, such as habitat structure, prey
abundance, prey vulnerability, prey availability, rainfall/
weather conditions, seasonality and the presence of competi-
tors (Patterson et al., 2004; Owen-Smith & Mills, 2008). These
ecological factors may determine the level at which prey selec-
tion can occur. For instance, large terrestrial carnivores tend
to select larger prey species, particularly in very productive
environments (Karanth & Sunquist, 1995). In the case of
large felids, vulnerability and availability of appropriately
sized prey seem to be the most important factors determining
prey selectivity. This pattern has been observed for tigers,
Panthera tigris (Karanth & Sunquist, 1995; Bagchi, Goyal &
Sankar, 2003), lions, Panthera lion (Owen-Smith & Mills,
2008), jaguars, Panthera onca (Azevedo & Murray, 2007a),
leopards, Panthera pardus (Hayward et al., 2006), and
cougars, Puma concolor (Husseman et al., 2003) feeding pref-
erentially on the most vulnerable prey species. In addition,
seasonality (wet and dry seasons) may be important to deter-
mine selectivity by terrestrial carnivores towards certain prey
species, prey age and gender (Pole et al., 2004). For instance,
variation in rainfall levels has been suggested to affect the
vulnerability of certain prey to predation by lions due to
changes in vegetative cover and food resources (Owen-Smith
& Mills, 2008). Therefore, an evaluation of the conditions
affecting the relative vulnerability of prey species can be of
paramount importance for understanding the dynamics of
predator–prey interactions.
Despite advances in the understanding of ecological factors
determining predator–prey interactions and a strong theoreti-
cal background on diet selection by predators, few studies
have investigated prey vulnerability and selection patterns of
large felids in tropical regions. As one of the most secretive of
all tropical large cats, the jaguar has been little studied regard-
ing patterns of prey selection. Generally considered as oppor-
tunistic feeders, jaguars include a wide variety of prey in their
diet, but selectivity does occur towards large- and medium-
Journal of Zoology
Journal of Zoology. Print ISSN 0952-8369
Journal of Zoology •• (2011) ••–•• © 2011 The Authors. Journal of Zoology © 2011 The Zoological Society of London 1
sized prey species (Gonzalez & Miller, 2002). This pattern is
more pronounced in productive environments where prey
base is abundant (Polisar et al., 2003). However, large home
ranges, wide dietary breadth and dense forested habitats have
precluded precise quantification of diet constituents and accu-
rate sampling techniques for determining available prey base
in most of the jaguar’s geographical range.
In the Pantanal region of Brazil, predation of caiman,
Caiman yacare, by jaguars provides a unique opportunity to
test predictions regarding prey selection. First, an interesting
ecological interaction emerges as both jaguar and caiman are
large predators and predation of caiman by jaguar outside the
region has only been reported in Venezuela (Polisar et al.,
2003). Second, caiman are mainly active in water and may be
more vulnerable to jaguars because jaguars prefer forested
habitat with standing water and are often found on river and
lake banks (Quigley & Crawshaw, 1992). Third, seasonality
may be an important factor affecting predator–prey interaction
in the region as it is the driving force in the Pantanal ecosystem.
With the onset of the wet season in the Pantanal, most caiman
often leave lake and river areas and travel long distances
(Coutinho & Campos, 1996), which apparently makes indi-
viduals more vulnerable to predation (Campos et al., 2006).
Indeed, flooding and predation by medium-sized carnivores
are the main causes of mortality of crocodilian eggs (Campos,
1993). Finally, caiman are highly abundant in the Pantanal and
may represent an important prey item to jaguars. Population
estimates indicate that there may be as many as 35 000 000
non-hatchling caiman in the whole Pantanal (Mourão et al.,
2000), although density may vary locally.
We examined patterns of jaguar predation on caiman in the
southern Pantanal, Brazil. Despite the high local caiman
abundance in the area, a previous study reported jaguar pre-
dation to be less than expected with little or no selectivity
(Azevedo & Murray, 2007a). Our objectives were to investi-
gate factors that may affect predation rates and vulnerability
of caiman to predation by jaguars at three levels. On an
intraspecific scale, we analysed patterns of jaguar predation
among different caiman body sizes to determine whether selec-
tion was driven by body size. On a spatial scale, we analysed
jaguar kill sites to determine whether habitat factors affect
caiman vulnerability to predation by jaguars. On a temporal
scale, we analysed the influence of temporal variation to quan-
tify the effect of rainfall on jaguar predation rates on caiman.
We hypothesized that (1) jaguar would prey indiscriminantly
over a broad range of caiman body sizes; (2) jaguar kills would
not be disproportionate in sites where caiman and jaguar both
forage, indicating that other factors influence vulnerability to
predation; (3) jaguar depredation patterns would be uniform
throughout the year.
Methods
Study area
The study was conducted in the southern part of the Pantanal
region in the state of Mato Grosso do Sul in Brazil (20°05’S
and 56°36’W) during February 2003–December 2008. The
Pantanal is a floodplain covering approximately 140 000 km2
of land on the borders of Bolivia and Paraguay. The Pantanal
is characterized by an annual regime of flooding and lowland
relief, with the landscape being composed of wetlands, season-
ally inundated grasslands and woodlands, and non-flooding
forests. The study site is a working 150 km2cattle ranch/
wildlife reserve, located in the southern region of the state.
Three major habitat types occur on the ranch: (1) open areas,
with grasslands composed mainly of grass species interspersed
with palm trees such as the carandá, Copernicia australis, and
acuri palms, Attalea phalerata, and commercial rice fields; (2)
closed woodlands constituting a one-story forest with trees
such as the ipê (Tabebuia sp.) lacking clear vertical stratifica-
tion and a grass understory that is flooded during wet season;
(3) semi-deciduous forests having vertical differentiation,
including ipê and acuri palms (Dubs, 1994).
Sampling method
The density of all sizes/age classes of caiman in the study area
based on systematic night counts in permanent rice irrigation
canals and swamps was reported to be approximately 16.4
2.1 individuals km-2(mean se), yielding a biomass of
327.3 kg km-2(Azevedo & Murray, 2007a). Rainfall data were
taken from the weather station at San Francisco Ranch.
Average annual precipitation at the study site between 2003
and 2008 was 1393.2 mm (197.6). We considered wet season
commenced when a threshold of monthly rain reached
100 mm for more than 2 consecutive months. Wet seasons
usually comprised the period between October and April and
dry seasons from May to September.
Caiman captures
We captured caiman in permanent rice irrigation canals,
swamps and along a tributary of the Miranda River from June
to September 2008. We attempted to capture caiman with
different body sizes in order to represent a wide spectrum of
body sizes and both gender. Capture techniques consisted of
approaching the animals on foot or by boat at night with a
spotlight. Animals were then snared and physically restrained
during data collection. No chemical immobilization was used.
Animal handling procedures were approved by IBAMA, the
Brazilian Environment Institute.
Body- and head-length measurements
Three body-length and 11 head-length variables were taken
from captured animals, as described by Hall & Portier (1994).
Body measurements such as the snout–vent length (SVL; cm)
were taken with a tape measure (1 mm precision). Head meas-
urements were taken with a caliper (.02 mm precision). Body
mass (BM) was taken with Pesola hanging scales (PESOLA
AG, Baar, Switzerland). The gender of caiman was deter-
mined through manual probing of the cloaca and/or visual
examination of genital morphology (Allstead & Lang, 1995)
with a speculum of appropriate size.
Jaguar predation on caiman F. C. C. Azevedo and L. M. Verdade
2Journal of Zoology •• (2011) ••–•• © 2011 The Authors. Journal of Zoology © 2011 The Zoological Society of London
We used measurements from living animals captured to
predict the BM (kg) in from body and head measurements by
general linear regression. We used quadratic regression
because some proportions on caiman skulls accelerate or
decelerate on the inflexion during ontogenetic process
(Verdade, 2000). We then used these equations to estimate the
size distribution of a collection of predated caiman from skulls
collected in the study area between 2003 and 2008. We took
three cranial measurements from the skulls: dorsal cranium
length (DCL), snout length (SL) and cranium width (CW).
Measurements of captured animals were also used to deter-
mine whether there was a significant morphometric variation
between male and female caiman using multivariate statistical
analysis. We compared BM of captured caiman with esti-
mated BM of caiman predated by jaguars using t-tests in order
to analyse whether selection was driven by size.
Predator consumption of caiman
Predator consumption of caiman was determined from analy-
ses of kills found in the study area. Carcasses of caiman were
found opportunistically while checking transects or by the
presence of vultures. Transects have been systematically used in
the study area to estimate the density of potential jaguar prey
species (Azevedo & Murray, 2007a). Predation of caiman,
specifically by jaguars, was determined if 2 of the following
were observed: signs of bites on carcasses, presence of scats
near kill sites, presence of fresh tracks near the site, cached
remains or signs of a trail where the prey had been carried or
dragged. The presence of such signs indicated death due to
predation by jaguar, herein called predation, as opposed to
other mortality causes, for instance, hunting, diseases, drought
and undetermined causes, herein called nonpredation.
The estimated area where carcasses could be reasonably
found due to habitat accessibility represented 60% of the total
area of the ranch (see Azevedo & Murray, 2007a). Whenever
possible, we performed necropsies on caiman found dead from
2003 to 2008 to evaluate the probable cause of death. We
collected skulls of predated caiman and recorded information
on the precise location using a Global Positioning System
(GPS) unit. We later used GPS locations of predation and
nonpredation mortalities to estimate habitat type and prox-
imity to nearest forest and water.
Vulnerability to predation
We used logistic regression to investigate the importance of
habitat factors such as forest and standing water on caiman
predation risk. We used cause of mortality (predation vs. non-
predation causes) as the dependent variable. The distance
(meters) of dead caiman from the nearest forest and water were
treated as independent variables. To assess the extent that
proximity to suitable habitat affected caiman vulnerability to
predation, we performed simple correlation analyses using
distance from nearest forest or water versus the number of
carcasses of caiman killed by jaguars. For comparison, we also
examined distance from nearest forest or water versus the
number of nonpredation carcasses within the study site. We
tested data for normality using the Kolmogorov–Smirnov test
for goodness-of-fit. When variances were comparable, we used
t-tests; otherwise, we used nonparametric Mann–Whitney tests
(U). The fit of regression models was compared using Akaike’s
information criterion, with the Akaike weights (wi) for each
model serving as evidence that the ith model is actually the best
model of the models being considered given the data (Burnham
& Anderson, 1998). We also measured the association between
death due to predation by jaguars and due to nonpredation
causes in relation to distance to forests and water sources using
the odds ratio (OR) produced by the logistic regression, i.e. the
relative amount by which the odds of predation by jaguars
increase (OR greater than 1.0) or decrease (OR less than 1.0)
when the distance to forests and water sources is increased by
1.0 unit (meters). Probability levels were two-tailed in all analy-
ses of determinants of prey mortality.
Temporal variation
The impact of jaguar predation on caiman was annually cal-
culated based on a kill proportion (K) as follows: K=S/A,
where Sis the number of events of caiman predation by
jaguars recorded in a year and Ais the total number of
deaths (predation and nonpredation causes) recorded in that
year. To investigate temporal patterns of predation of
caiman by jaguars, we compared seasonal distribution of
mortality factors using Pearson chi-square tests. To assess
the effect of seasonality on predation, we investigated the
correlations between annual, seasonal and monthly killings
of caiman and available local records of rainfall totals by
year, season (wet/dry) and month for 2003–2008 using
bivariate correlation analysis. We also attempted to predict
caiman annual and monthly kill proportion from available
local records of rainfall totals by year and month using
simple regression analysis. We performed analysis of the
temporal autocorrelation of the kills using monthly intervals
with time lags of 12 months using the autocorrelation func-
tion of SPSS (Statistical Package for the Social Sciences
Inc., Chicago, IL, USA, 2008.). Assumptions of normality
were met by our temporal data; therefore, we used paramet-
ric tests in our correlation analyses.
Results
Caiman biometry
We captured 33 caiman. Their mean SVL was 79.1 24.2 cm
(sd) (range: 39.0–129.0) and the mean BM was 15.7
14.0 kg (range: 1.2–55.0 kg). Male caiman comprised 60.6% of
our sample. Male caiman (SVL =86.5 25.6 mm; mean sd)
were longer than female caiman (67.8 17.4 mm) [t=2.30,
degrees of freedom (d.f.) =31, P=0.028]. In addition, male
caimans (BM =19.7 15.9 kg, n=20) were marginally
heavier than female caimans (9.6 7.4 kg, n=13) (U=81.5,
P=0.074). However, no sexual dimorphism in head and body
form was observed (multivariate analysis of variance – Pillai’s
trace criterion: F=1.630; d.f. =14, P=0.163). DCL was the
F. C. C. Azevedo and L. M. Verdade Jaguar predation on caiman
Journal of Zoology •• (2011) ••–•• © 2011 The Authors. Journal of Zoology © 2011 The Zoological Society of London 3
most accurate predictor of BM estimation for caiman (DCL
Radj2=0.983, n=21; Table 1). Using DCL equation, it was
possible to estimate BM of living caiman from skulls
(Table 2).
Caiman consumption by jaguars
For the entire study period, we recorded 114 caiman mortali-
ties. Predation accounted for 62.3% (n=71), while nonpreda-
tion accounted for 37.7% (n=43) of all caiman found dead.
We were able to retrieve a random sample of 22 skulls of
caiman predated by jaguars from 2003 to 2008. Their esti-
mated BM was 27.87 14.4 kg (mean sd). Jaguars choose
prey across a wide range of caiman body mass, from subadults
to adults (estimated BM range: 6.8–49.2 kg). We found that
caiman predated by jaguars were heavier than captured
caiman (t=-2.91, d.f. =53, P=0.005).
Vulnerability to predation
Our analysis on the importance of habitat factors in caiman
mortality for our study area suggested that distance to forest
was the most important variable explaining cause of mortality
(Table 3). The habitat-related OR for the best model [0.994;
95% confidence interval (CI) =0.991–0.998] indicated that
probability of death from jaguar predation decreases as dis-
tance to forest increases. Indeed, based on carcass locations,
the number of caiman killed by jaguars decreased with
increased distances from both forest (r=-0.639, n=71) and
water (r =-0.734, n=71). Those carcasses determined not to
be killed by jaguars did not have a significant correlation with
either distance to forest (r=-0.422, n=43) or distance to
water (r=-0.256, n=43). However, when comparing the
average distances to forest, locations of caiman killed by
jaguars (160.79 274.33 m, n=68) were closer to forest (U=
1135, P=0.048) than those not killed by jaguars (305.63
462.25 m, n=43). In contrast, distances to water were similar
(U=1420, P=0.799) between caiman killed by jaguars (38.18
95.05 m, n=68) and caiman not killed by jaguars (91.58
233.03 m, n=43).
Temporal patterns of killings
Our results yielded 11.8 5.8 caiman mortalities annually by
jaguars and a monthly average of 1.0 0.6 (sd) caiman
mortalities by jaguars. The autocorrelation function value of
monthly jaguar predation on caiman was not significant (all
P>0.950) at any time-lag intervals. We therefore considered
jaguar killing of caiman to be independent of monthly time
Table 1 Regression equations between body- and head-size measurements and the body mass in Pantanal caiman, Caiman yacare (y=a+bx +cx2).
Xa(SE)b(SE)c(SE)Radj2SE P
DCL 9.49 (3.63) -1.90 (0.38) 0.11 (0.01) 0.98 1.85 <0.001
WSR 6.50 (4.09) -2.56 (0.76) 0.30 (0.03) 0.97 2.19 <0.001
CW 4.76 (4.37) -1.95 (0.73) 0.22 (0.03) 0.97 2.45 <0.001
SW 6.86 (5.34) -3.60 (1.21) 0.49 (0.06) 0.97 2.59 <0.001
SL 4.24 (4.17) -1.85 (0.77) 0.25 (0.03) 0.96 2.74 <0.001
WN 13.83 (5.50) -20.57 (5.14) 9.20 (1.13) 0.96 2.74 <0.001
LCR 21.38 (10.74) -18.01 (5.22) 3.92 (0.62) 0.95 3.14 <0.001
IOW 2.34 (6.49) -7.87 (7.75) 8.77 (2.16) 0.90 4.43 <0.001
OL -13.97 (15.55) 1.17 (7.72) 1.70 (0.93) 0.86 5.25 <0.001
OW 5.19 (32.25) -20.18 (24.71) 9.41 (4.64) 0.83 5.78 <0.001
DCL, dorsal cranial length; WSR, surangular width; CW, cranial width; SW, basal snout width; SL, snout length; WN, maximal width of external nares;
LCR, length of the postorbital cranial roof; IOW, minimal orbital length; OL, maximal orbital length; OW, maximal inter-orbital width; SE, standard error
of the constants and the regression coefficient.
Table 2 Estimated body mass (BM) of 22 predated caiman, Caiman
yacare. Body mass in kilograms was predicted by linear regression from
dorsal cranial length (DCL) measured from skulls collected from 2003 to
2008. (BM =9.5 -1.9x+0.1x2).
X(DCL) BM
27.8 41.33
27.7 40.92
18.3 11.43
20.5 16.60
28.8 45.63
28.7 45.19
a9.49
28.3 43.46
19.0 12.96
15.8 6.85
27.4 39.68
29.6 49.22
25.4 31.92
26.2 34.92
26.9 37.66
18.0 10.81
21.5 19.30
25.0 30.47
18.2 11.22
20.1 15.58
19.8 14.84
23.5 25.35
aBody mass predicted from cranium width measured from a skull par-
tially broken.
Jaguar predation on caiman F. C. C. Azevedo and L. M. Verdade
4Journal of Zoology •• (2011) ••–•• © 2011 The Authors. Journal of Zoology © 2011 The Zoological Society of London
intervals. The highest number of mortalities occurred in Sep-
tember (Fig. 1a). Temporal variation on caiman predation
suggested there was an association between season and
cause of mortality. Proportion of caiman mortalities in wet
versus dry seasons differed significantly (c21=4.60, P<
0.001). During dry seasons, 72.7% (n=40) of deaths were
due to predation, while 27.3% (n=15) were due to other
causes (Fig. 1b). During wet seasons, 52.5% (n=31) of
mortalities were due to predation, while 47.5% (n=28) were
due to other causes (Fig. 1). During dry seasons, caiman
mortalities were 2.2 times more likely to occur due to preda-
tion than due to other causes (OR =2.2), and more predation
mortalities occurred in 2007 (n=19; 26.8% of all killings)
(Fig. 1c).
Correlation between caiman mortality and local records of
rainfall indicated no significant relationship between annual
and monthly caiman mortality and rainfall totals by year and
month (r=0.130, P=0.807, n=6; r=-0.316, P=0.317, n=12,
respectively). A similar pattern was observed between sea-
sonal mortalities and rainfall by season. Caiman killings were
not correlated with local rainfall during dry (r=-0.583, P=
0.224, n=6) or wet seasons (r=-0.092, P=0.863, n=6). Our
results suggested that no significant relationship between
caiman’s annual and monthly mortality proportions could be
predicted by rainfall totals either yearly or monthly (Radj2=
-0.234, P=0.831, n=6; Radj2=0.164, P=0.106, n=12,
respectively).
Discussion
Our results indicate that predation by jaguars was more
important than other forms of mortality in caiman popula-
tion. However, the proportions of mortalities due to jaguar
predation that we report may be underestimates. Although we
did not test for differences in probability of detection of car-
casses, our sample may have been biased in favor of carcasses
of caiman not killed by jaguars. Jaguar’s behavior with their
kills may make caiman killed by jaguars harder to find than
caiman carcasses not killed by jaguars.
Our data suggest that caiman predation by jaguars varied
between years, heavier in 2003, 2007 and 2008 and lower in
2005 and 2006 (Fig. 1c). Similar to other studies where large
felids’ predation upon wildlife increases during dry seasons
(Patterson et al., 2004), in our study, caiman mortality was
2.2 times more likely to occur due to predation than due to
other causes during dry seasons. Indeed, predation risk of
caimans by jaguars was particularly heavy at the peak of dry
seasons in September. During wet seasons, caiman mortality
Table 3 Logistic regression models of variables found to be significant in predicting causes of caiman, Caiman yacare, mortality (predated vs. other
causes) on San Francisco Ranch, Brazil during January–December 2003–2008 as ranked by Akaike information criterion (AIC), where the other cause
is the reference cell
ModeliOR1OR2CI1CI2KiDiwi
Forest 0.994 – 0.991–0.998 – 2 0.00 0.62
Forest +water 0.994 1.001 0.991–0.998 0.999–1.003 3 1.01 0.38
Water 1.001 – 0.999–1.003 – 2 22.41 0.00
Constant 1.581 – 1 22.40 0.00
For each modeli,Kiis the number of parameters in the model, Diis the change in AIC between the model and the model with the lowest AIC (best
model) and wiis the Akaike weight. Odds ratio (OR) and the corresponding 95% confidence interval (CI) are provided. Model significance was
determined by the likelihood ratio test. Forest and water models represent distance to forests and distance to water, respectively. OR indicates the
relative amount by which the odds of predation by jaguars increase (OR greater than 1.0) or decrease (OR less than 1.0) when the distance to forests
and water sources is increased by 1.0 unit (meters).
16
14
12
10
8
6
4
2
0
Jan Feb Mar Apr MayJun Jul Aug Sep Oct Nov Dec
Months from 2003 to 2008
Number of caiman found dead
Number of caiman deaths
Number of caiman dead
Predation
Predation dry
Predation wet
Nonpredation
Predation
Nonpredation
Nonpredation dry
Nonpredation wet
14
12
10
8
6
4
2
0
Years
2003 2004 2005 2006 2007 2008
Years
2003 2004 2005 2006 2007 2008
20
18
16
14
12
10
8
6
4
2
0
(a) (b) (c)
Figure 1 Monthly (a), seasonal (b) and annual (c) patterns of predation and nonpredation mortality of caiman, Caiman yacare (n=114) recorded at
San Francisco Ranch, Pantanal region, Brazil, from 2003 to 2008.
F. C. C. Azevedo and L. M. Verdade Jaguar predation on caiman
Journal of Zoology •• (2011) ••–•• © 2011 The Authors. Journal of Zoology © 2011 The Zoological Society of London 5
associated with jaguar predation was similar to other mor-
tality causes. The concentration of predation cases during
dry seasons seems to be related to the highest density of
caiman congregated in a few sites containing water of a suit-
able depth (Campos, Coutinho & Magnusson, 2003) and to
the longer caiman movement distances during dry seasons,
up to 10 km (Schaller & Crawshaw, 1980). Therefore, we
might tentatively conclude that jaguar predation on caiman
seems to be seasonally influenced. However, we could not
test for the possibility of variability in our carcass detection
by season or habitat. As any variability in this probability
could affect our results, our ability to speculate further is
limited.
Our results indicated that caiman predation by jaguars
was influenced by distance to forests. While the distribution
of carcasses of predated caiman was negatively associated
with distance to closest forest, those carcasses of nonpreda-
tion causes were not. In general, forests provide cover for
predators while stalking prey (Husseman et al., 2003). The
importance of forests with regard to vulnerability of live-
stock to predation by jaguars has already been reported in
the Pantanal region, where livestock predation risk increased
with proximity to forest cover declined (Azevedo & Murray,
2007b). A similar pattern was found in Southern Amazon
for cattle depredation by pumas and jaguars (Palmeira et al.,
2008). Adult caiman in the Pantanal are known to move
long distances in short periods of time (Campos et al., 2006),
which could increase their vulnerability to predation with
increasing distances from permanent water sources. Indeed,
our results indicate different correlation patterns of caiman
mortalities due to predation or nonpredation causes in rela-
tion to closest permanent water sources, suggesting that dis-
tance to water did influence caiman predation by jaguars.
While the distributions of caiman carcasses killed by jaguar
decreased with increased distance to water, those caiman
carcasses not killed by jaguar did not. In the Pantanal, the
availability of ephemeral water bodies that persist through-
out the first months of the dry season likely reflected the lack
of influence of permanent water sources on the vulnerability
of cattle to predation by jaguars. Cattle can find water to
drink during dry seasons even far from permanent water
sources (Azevedo & Murray, 2007b). Contrary to what has
been reported for jaguar depredation on livestock in the
Pantanal, caiman seemed to be more dependent on perma-
nent water holes not only for food resources but also to
increase their chance to escape from jaguar attacks. Caiman
probably find refuge from predation by jaguars in deep
water.
As reported for other large predators that spend most of
their time near available water sources where they can find and
kill prey during dry seasons (Patterson et al., 2004), we specu-
late that jaguars concentrate their hunting near those perma-
nent water sites to increase their hunting success. Such
vulnerability seems to decrease during wet seasons when
flooding yields a very rich and productive habitat in which
caimans disperse (Junk et al., 2006). However, even though
more predation occurred during dry seasons, we found no
significant relationship between local rainfall levels and
caiman predation by jaguars. Our results suggest that neither
annual nor monthly rainfall totals at the study site influenced
predation of caiman by jaguars. Although rainfall has been
reported as an explanatory variable for predation patterns in
ecosystems where an array of large predators and prey interact
(Owen-Smith & Mills, 2008), local precipitation was not rel-
evant in the present study. A possible explanation for this
pattern is that the water level in Pantanal is determined by
precipitation upstream from a huge drainage, including vast
areas of Cerrado and the Amazon forest. In fact, the annual
flooding regime as a consequence of the rainfall in the whole
drainage seems to be more decisive for jaguar prey selection
(Crawshaw & Quigley, 1991).
In general, there is a bias in predation towards younger
individuals (Temple, 1987). Although body masses of the
carcasses of caiman killed by jaguars were estimates from the
regression equations and have an additional source of error
associated with them, our findings regarding the range of
estimated body masses for caiman killed by jaguars support
the hypothesis that jaguars prey upon a wide range of
caiman body sizes, including adult male and female caimans.
In addition, despite the fact that captures and carcass recov-
eries may have different biases towards smaller or larger
caimans, our results suggest that jaguars selected heavier
caiman compared with captured caiman. As a result, in areas
with jaguars, such as the Pantanal, we can expect a shorter
reproductive period and, consequently, a faster turnover of
reproductive male and female jaguars. Under these circum-
stances, the local extinction of the jaguar, which has already
occurred on a significant part of its range, could potentially
affect behavioral ecology and reproductive success of
caiman, with regard to mating systems, recruitment, disper-
sal patterns, use of areas near or in forests and population
genetics.
Our results indicate that the caiman population structure
in our study area was male biased, and male caimans were
larger than female caimans, which is similar to the pattern
found in other central areas of the Pantanal region (Campos,
Coutinho & Magnusson, 2003). However, we did not find any
evidence of cranial sexual dimorphism in Pantanal caiman as
described for other species such as the American alligator
(Viosca, Jr, 1939), the Philippine’s crocodile (Hall & Portier,
1994) and the broad-snouted caiman (Piña et al., 2007). This
unexpected pattern should be prioritized in future studies and
could possibly be related to the species social behavior (Vliet,
1989).
The jaguar occurs throughout the geographic range of
caimans. However, jaguars have undergone local extinction in
many areas due to human impacts. Caiman, which are an
important prey species for jaguar, may also be affected as we
describe here. Further research on the influence of jaguar local
extinctions on caiman populations, behavior and genetics
should be prioritized in future studies.
Acknowledgements
We thank FAPESP for providing funds for the study
(FAPESP Biota Program, Proc. Nos. 2006/60954-4 and 2007/
Jaguar predation on caiman F. C. C. Azevedo and L. M. Verdade
6Journal of Zoology •• (2011) ••–•• © 2011 The Authors. Journal of Zoology © 2011 The Zoological Society of London
00976-7). Marina Lacorte, Nuno Pedroso, Luis Rosalino,
Emilie Henst, Cynthia Widmer, Phil Wilkinson, Christy
Wilkinson and Allan Woodward participated on data collec-
tion from living caiman. Instituto Pró-Carnívoros and San
Francisco Ranch provided logistics. We thank Henrique
Concone and Ricardo Costa for the help with mortality
surveys. We thank Jocelyn Aycrigg for constructive comments
on this paper.
References
Abrams, P. & Matsuda, P. (1993). Effects of adaptive preda-
tory anti-predator behavior in a two-prey-one-predator
system. Evol. Ecol. 7, 312–326.
Allstead, J. & Lang, J.W. (1995). Sexual dimorphism in the
genital morphology of young American alligators, Alligator
mississippiensis.Herpetologica 51, 314–325.
Azevedo, F.C.C. & Murray, D.L. (2007a). Spatial organiza-
tion and food habits of jaguars (Panthera onca) in a flood-
plain forest. Biol. Conserv. 137, 391–402.
Azevedo, F.C.C. & Murray, D.L. (2007b). Evaluation of
potential factors predisposing livestock to predation by
jaguars. J. Wildl. Manage. 71, 2379–2386.
Bagchi, S., Goyal, S.P. & Sankar, K. (2003). Prey abundance
and prey selection by tigers (Panthera tigris) in a semi-arid,
dry deciduous forest in western India. J. Zool. (Lond.) 260,
285–290.
Burnham, K.P. & Anderson, D.R. (1998). Model selection and
inference: a practical information-theoretic approach. New
York: Springer-Verlag.
Campos, Z. (1993). Effect of habitat on survival of eggs and
sex ratio of hatchlings of Caiman crocodilus yacare in the
Pantanal, Brazil. J. Herpetol. 27, 127–132.
Campos, Z., Coutinho, M. & Magnusson, W.E. (2003). Ter-
restrial activity of caiman in the Pantanal, Brazil. Copeia 3,
628–634.
Campos, Z., Coutinho, M., Mourão, G.M., Bayliss, P. &
Magnusson, W.E. (2006). Long distance movements by
Caiman crocodiles yacare: implications for management of
the species in the Brazilian Pantanal. Herpetol. J. 16, 123–
132.
Coutinho, M. & Campos, Z. (1996). Effect of habitat and sea-
sonality on the densities of caiman in southern Pantanal,
Brazil. J. Trop. Ecol. 12, 741–747.
Crawshaw, P.G. & Quigley H. (1991). Jaguar spacing, activity
and habitat use in a seasonally flooded environment in
Brazil. J. Zool. 223, 357–370.
Dubs, B. (1994). Differentiation of woodland and wet savanna
habitats in the Pantanal of Mato Grosso, Brazil. Disserta-
tion, University of Zürich, Edinburgh, UK.
Gonzalez, C.A.L. & Miller, B.J. (2002). Do jaguars Panthera
onca depend on large prey. West. North Am. Nat. 62, 218–
222.
Hall, P.M. & Portier, K.M. (1994). Cranial morphometry of
New Guinea crocodiles (Crocodylus novaeguineae): ontoge-
netic variation in relative growth of the skull and an assess-
ment of its utility as a predictor of the sex and size of
individuals. Herpetol. Monogr. 8, 203–225.
Hayward, M.W., Henschell, P., O’Brien, J., Hofmeyr, M,
Balme, G. & Kerley, G.H.I. (2006). Prey preferences of
the leopard (Panthera pardus). J. Zool. (Lond.) 270, 298–
313.
Husseman, J.S., D.L. Murray, G. Power, C. Mack, C.R.
Wenger & H. Quigley (2003). Assessing differential prey
selection patterns between two sympatric large carnivores.
Oikos 101, 591–601.
Junk, W.J., Cunha, C.N., Wantzen, K.N., Petermann, P.,
Strüssmann, C., Marques, M.I. & Adis, J. (2006). Biodiver-
sity and its conservation in the Pantanal of Mato Grosso,
Brazil. Aquat. Sci. 68, 278–309.
Karanth, K.U. & Sunquist, M.E. (1995). Prey selection by
tiger, leopard and dhole in tropical forests. J. Anim. Ecol.
64, 439–450.
MacArthur, R.H. & Pianka, E.R. (1966). On the optimal use
of a patchy environment. Am. Nat. 100, 603–609.
Mourão, G. M., Coutinho, M., Mauro, R., Campos, Z.,
Tomás, W. & Magnusson, W. E. (2000). Aerial surveys of
caiman, marsh deer and pampas deer in the Pantanal
wetland of Brazil. Biol. Conserv. 92, 175–183.
Owen-Smith, N. & Mills, M.G.L. (2008). Shifting prey
selection generates contrasting herbivore dynamics within
a large-mammal predator-prey web. Ecology 89,
1120–1133.
Palmeira, F.B.L., Crawshaw, P.G., Jr, Haddad, C. M.,
Ferraz, K.M.P.M. & Verdade, L.M. (2008). Cattle depreda-
tion by puma (Puma concolor) and jaguar (Panthera onca)
in Northern Goiás, Central-Western Brazil. Biol. Conserv.
141, 118–125.
Patterson, B.D., Kasiki, S.M., Selempo, E. & Kays. R.W.
(2004). Livestock predation by lions (Panthera leo) and
other carnivores on ranches neighboring Tsavo National
Parks, Kenya. Biol. Conserv. 119, 507–516.
Persson, L. & Greenberg, L.A. (1990). Optimal foraging and
habitat shifts in perch (Perca fluviatilus) in a resource gradi-
ent. Ecology 71, 1699–1713.
Piña, C.I., Larriera, A., Siroski, P. & Verdade. L.M. (2007).
Cranial sexual discrimination in hatchling broad-snouted
caiman (Caiman latirostris). Iheringia Ser. Zool. 97, 17–20.
Pole, A., Gordon, I.J., Gorman, M.L. & MacAskill, M.
(2004). Prey selection by African wild dogs in southern
Zimbabwe. J. Zool. (Lond.) 262, 207–215.
Polisar, J., Maxit, I., Scognamillo, D., Farrel, L., Sunquist,
M.E. & Eisenberg, J.E. (2003). Jaguars, pumas, their prey
base, and cattle ranching: ecological interpretations of a
management problem. Biol. Conserv. 109, 297–310.
Quigley, H.B. & Crawshaw, P.G., Jr (1992). A conservation
plan for the jaguar Panthera onca in the Pantanal region of
Brazil. Biol. Conserv. 61, 149–157.
Schaller, G.B. & Crawshaw P.G. Jr. (1980). Movement pat-
terns of jaguar. Biotropica 12, 161–168.
F. C. C. Azevedo and L. M. Verdade Jaguar predation on caiman
Journal of Zoology •• (2011) ••–•• © 2011 The Authors. Journal of Zoology © 2011 The Zoological Society of London 7
Temple, S.A. (1987). Do predators always captured substand-
ard individuals disproportionately from prey populations?
Ecology 68, 116–125.
Verdade, L.M. (2000). Regression equations between body
and head measurements in the broad-snouted caiman
(Caiman latirostris). Rev. Bras. Biol. 60, 469–482.
Viosca, P., Jr (1939). External sexual differences in the
alligator, Alligator mississippiensis.Herpetologica 1,
154–155.
Vliet, K.A. (1989). Social displays of the American alligator.
Am. Zool. 29, 1019–1031.
Jaguar predation on caiman F. C. C. Azevedo and L. M. Verdade
8Journal of Zoology •• (2011) ••–•• © 2011 The Authors. Journal of Zoology © 2011 The Zoological Society of London
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