Chimpanzee Predation Research Articles

Wild chimpanzees (Pan troglodytes troglodytes) exploit tortoises (Kinixys erosa) via percussive technology

Chimpanzees (Pan troglodytes), one of humankinds’ closest living relatives, are known to hunt and consume the meat of various animal taxa. Although some researchers have presented indirect evidence that chimpanzees may also prey on tortoises, until now, direct observations of this behaviour did not exist. Here, we provide systematic descriptions of the first observations of chimpanzee predation on tortoises (Kinixys erosa). We made these unprecedented observations on newly habituated chimpanzees (Pan troglodytes troglodytes) of the Rekambo community, living in the Loango National Park, Gabon. The behaviour qualified as customary, that is occurring in most or all adult males, involved a distinct smashing technique, and resulted frequently in food sharing with other group members. Our observations shed new light on the hitherto little understood percussive technology of chimpanzees, and expand our current knowledge on chimpanzees’ dietary and predatory repertoires with respect to reptiles. We also report a case of food storage and discuss it in the context of future-oriented cognition. Our findings suggest the need for more nuanced interpretations of chimpanzees’ cognitive skills in combination with an in-depth understanding of their unique socio-ecological niches. They further emphasize the importance of nonhuman primate field observations to inform theories of hominin evolution.

Infanticide in chimpanzees: Taphonomic case studies from Gombe.

We present a study of skeletal damage to four chimpanzee (Pan troglodytes) infanticide victims from Gombe National Park, Tanzania. Skeletal analysis may provide insight into the adaptive significance of infanticide by examining whether nutritional benefits sufficiently explain infanticidal behavior. The nutritional hypothesis would be supported if bone survivorship rates and skeletal damage patterns are comparable to those of monkey prey. If not, other explanations, such as the resource competition hypothesis, should be considered. Taphonomic assessment of two chimpanzee infants included description of breakage and surface modification, data on MNE, %MNE, and bone survivorship. Two additional infants were assessed qualitatively. The data were compared to published information on monkey prey. We also undertook a review of published infanticide cases. The cases were intercommunity infanticides (one male and three female infants) committed by males. Attackers partially consumed two of the victims. Damage to all four infants included puncture marks and compression fractures to the cranium, crenulated breaks to long bones, and incipient fractures on ribs. Compared to monkey prey, the chimpanzee infants had an abundance of vertebrae and hand/foot bones. The cases described here suggest that chimpanzees may not always completely consume infanticide victims, while reports on chimpanzee predation indicated that complete consumption of monkey prey usually occurred. Infanticidal chimpanzees undoubtedly gain nutritional benefits when they consume dead infants, but this benefit may not sufficiently explain infanticide in this species. Continued study of infanticidal and hunting behavior, including skeletal analysis, is likely to be of interest.

Physiological and Behavioral Effects of Capture Darting on Red Colobus Monkeys (Procolobus rufomitratus) with a Comparison to Chimpanzee (Pan troglodytes) Predation

Understanding how human activities affect wild primates is critical to the design of effective conservation strategies. Despite this need, few studies have examined the physiological and behavioral effects of field research methods in the wild. Here, we examine how the stress response, i.e., fecal cortisol, and behavior of Ugandan red colobus monkeys (Procolobus rufomitratus) in Kibale National Park are affected by chemical immobilization and collaring, i.e., capture. We compare this anthropogenic stressor to a naturally occurring stressor: a chimpanzee (Pan troglodytes) predation attack. Two adult males had peak cortisol levels of 283 and 284 ng/g 2–3 d after capture, which were 190% and 182% above their baseline levels, i.e., the first sample taken immediately after capture, but these peak levels did not remain elevated. Using long-term data, i.e., 11 mo of data, we found no difference in fecal cortisol levels between 10 darted and collared individuals and 14 individuals living in the same social group that were not darted or collared. For the chimpanzee attack, peak fecal cortisol levels (147–211% above baseline) were recorded 1–4 d after the attack, but these levels also did not remain elevated for long. These data show that darting and collaring and a chimpanzee predation attempt caused an acute stress response, but neither leads to sustained elevated cortisol levels. Thus, in situations in which research contributes significantly to the conservation of primates and cannot be conducted noninvasively, capture darting appears to be a useful technique with minimal long-term effects as long as injury and mortality are avoided. However, we encourage researchers to make similar physiological and behavioral comparisons in other field studies using similar techniques to provide a better understanding of the effects of research practices on the stress physiology and social behavior of wild primates.

Apes finding ants: Predator–prey dynamics in a chimpanzee habitat in Nigeria

Some chimpanzee populations prey upon army ants, usually with stick tools. However, how their prey's subterranean nesting and nomadic lifestyle influence the apes' harvesting success is still poorly understood. This is particularly true for chimpanzees (Pan troglodytes ellioti) at Gashaka/Nigeria, which consume army ants (Dorylus rubellus) with much higher frequency than at other sites. We assessed various harvesting and search options theoretically available to the apes. For this, we reconstructed annual consumption patterns from feces and compared the physical characteristics of exploited ant nests with those that were not targeted. Repeated exploitation of a discovered nest is viable only in the short term, as disturbed colonies soon moved to a new site. Moreover, monitoring previously occupied nest cavities is uneconomical, as ants hardly ever re-used them. Thus, the apes have to detect new nests regularly, although colony density is relatively low (1 colony/1.3 ha). Surprisingly, visual search cues seem to be of limited importance because the probability of a nest being exploited was independent of its conspicuousness (presence of excavated soil piles, concealing leaf-litter or vegetation). However, chimpanzees preferentially targeted nests in forests or at the base of food trees, that is, where the apes spend relatively more time and/or where ant colony density is highest. Taken together, our findings suggest that, instead of employing a search strategy based on visual cues or spatial memory, chimpanzee predation on army ants contains a considerable opportunistic element.

Chimpanzee‐red colobus encounter rates show a red colobus population decline associated with predation by chimpanzees at Ngogo

Chimpanzees (Pan troglodytes) hunt various primates, but concentrate on red colobus monkeys (Piliocolobus spp.) wherever the two species are sympatric. The extraordinarily large Ngogo chimpanzee community in Kibale National Park, Uganda, preys heavily on the local population of red colobus (P. tephrosceles). Census data showed a steep decline in this population in the center of the chimpanzees' home range between 1975 and 2007 [Lwanga et al., 2011; Teelen, 2007b]. Given no obvious change in food availability, predation by chimpanzees was the most likely cause [ibid.; Teelen, 2008]. However, census data from other parts of the home range raised the possibility that the decline was restricted to this central area [Teelen, 2007a] We present data from 1998 to 2012 on the rate of encounters between chimpanzees and red colobus that provide a chimpanzee-centered estimate of red colobus density, thus of predation opportunities, throughout the home range. These corroborate census data by showing a long-term decline in encounters near the center. They also show that encounters become relatively more common at increasing distances from the center, but encounter rates have decreased even in peripheral areas and, by implication, the red colobus population has declined throughout the study area. These data corroborate Teelen's [2008] conclusion that chimpanzee predation on red colobus during the 1990s and early 2000s was unsustainable. Hunting rates and prey offtake rates have also declined markedly; whether this will allow the red colobus population to recover is unknown. In contrast, rates at which chimpanzees encountered redtail monkeys (Cercopithecus ascanius) and grey-cheeked mangabeys (Lophocebus albigena) did not decrease. Neither did they increase, however, contrary to long-term census data from the center of the study area [Lwanga et al., 2011].

Army ant defensive behaviour and chimpanzee predation success: field experiments in Nigeria

AbstractAcross Africa, chimpanzees prey on army ants, typically using stick tools. Population differences in predation patterns reflect environmental as well as sociocultural factors. However, as for ecological constraints, we lack information about how the ants' defensive response unfolds over the course of a predatory attempt and how this influences chimpanzee reward. We studied these aspects of insectivory in the habitat of Nigerian chimpanzees through field experiments with previously used tools. The speed with which ants run up a tool decreased continuously during experimental dips into nests. This suggests that soldiers with long legs run up the tools first, before fanning out to deter the intruder. Workers attacking later on were increasingly smaller, thus running less fast. Yet, because more and more insects join the defence, harvesting yield (g dry weight) steadily increased for the first 17 min, to then drop markedly. We hypothesize that the length of dipping sessions by wild chimpanzees is limited by either diminishing return or discomfort caused by being continually bitten. Actual harvesting success cannot be reconstructed from ant remains in chimpanzee faeces without knowing what proportion of consumed insects is detectable in excreta. Through human self‐experiments, we found that only 10% of ingested ants are found in a subsequent excretion. Based on counts of ant heads in chimpanzee faeces, this translates into 12.9 g dry weight ingested per dipping session, which is far more than elsewhere. Although prey availability and harvesting technique varies across sites, our data still suggest a much greater yield for Nigeria. One reason for this may be a particular aggressiveness of Dorylus rubellus. While this is the only army ant species preyed upon in Nigeria, it is not regularly eaten elsewhere. Standardized experiments and faecal analyses across study sites will be necessary to better understand how ecological constraints influence chimpanzee myrmecophagy.

Primate population dynamics over 32.9 years at Ngogo, Kibale National Park, Uganda

We present census data for eight primate species spanning 32.9 years along the same transect at Ngogo, Kibale National Park, Uganda, demonstrating major changes in the composition of the primate community. Correlated with an estimated decline of ∼89% in the red colobus population was an increase in encounter rates with chimpanzee parties. Our data, along with the unusually high rates of predation by chimpanzees on red colobus at Ngogo and the fact that the chimpanzee community at Ngogo is the largest ever recorded, support the conclusion that the red colobus decline was caused primarily by chimpanzee predation. This seems to be the first documented case of predation by one nonhuman primate causing the population decline in another. We evaluated disease and interspecific competition as other possible causes of the red colobus decline, but judged them to be relatively insignificant compared with predation by chimpanzees. Notable changes in encounter rates with other primate species may have resulted from forest expansion. Those for mangabeys, redtails, and black and white colobus increased significantly. Encounter rates increased for l'Hoest's monkeys too, but the increased sightings may have been an artifact of increased habituation. Sightings of blue monkey and baboon groups declined. There was no significant change in encounter rates for all species combined. The Ngogo primate community seemed to be in a nonequilibrium state, changing from one dominated by two species, a folivore (red colobus) and a frugivorous omnivore (redtails), to one dominated by three species of frugivorous omnivores (redtails, mangabeys, and chimpanzees). This study demonstrates the importance of long-term monitoring in understanding population dynamics and the role of intrinsic variables in shaping the species composition of a community.

The nature of culture: Technological variation in chimpanzee predation on army ants revisited

Chimpanzee ( Pan troglodytes) predation on army ants ( Dorylus, subgenus Anomma) is an impressive example of skillful use of elementary technology, and it has been suggested to reflect cultural differences among chimpanzee communities. Alternatively, the observed geographic diversity in army-ant-eating may represent local behavioral responses of the chimpanzees to the anti-predator traits of the army ant species present at the different sites. We examined assemblages of available prey species, their behavior and morphology, consumption by chimpanzees, techniques employed, and tool lengths at 14 sites in eastern, central, and western Africa. Where army ants are eaten, tool length and concomitant technique are a function of prey type. Epigaeically foraging species with aggressive workers that inflict painful bites are harvested with longer tools and usually by the “pull-through” technique; species foraging in leaf-litter with less aggressive workers that inflict less painful bites are harvested with short tools and by the “direct-mouthing” technique. However, prey species characteristics do not explain several differences in army-ant-eating between Bossou (Guinea) and Taï (Ivory Coast), where the same suite of prey species is available and is consumed. Moreover, the absence of army-ant-eating at five sites cannot be explained by the identity of available prey species, as all the species found at these sites are eaten elsewhere. We conclude that some of the observed variation in the predator-prey relationship of chimpanzees and army ants reflects environmental influences driven by the prey, while other variation is not linked to prey characteristics and may be solely sociocultural.

Influence of chimpanzee predation on the red colobus population at Ngogo, Kibale National Park, Uganda

Frequent hunting of red colobus monkeys (Procolobus rufomitratus) takes place at all long-term chimpanzee (Pan troglodytes) study sites where both species are present. Red colobus are the most commonly selected prey of chimpanzees even when other monkey species are more abundant. In particular, the chimpanzee community at Ngogo, Kibale National Park, Uganda, preys heavily on red colobus monkeys: the chimpanzee hunting success rate is extremely high, and chimpanzees kill many individuals per successful hunt. Census data had suggested that the red colobus population is declining and that predation by chimpanzees may be contributing to this decline. In this paper, I address the impact of hunting on the red colobus population at Ngogo. To test the hypothesis that chimpanzee hunting is sustainable, I am using demographic data collected on red colobus monkeys over a period of 3 years, as well as fecundity and mortality data from previous studies of this species. I apply matrix models and vortex analyses using a sensitivity analysis approach to project future population development. Results show that current rates of hunting are not sustainable, but that chimpanzees are neither more "noble", nor more "savage" than humans are, but that they also hunt to ensure maximum benefit without regard for the consequences for the prey population.

Influence of Chimpanzee Predation on Associations Between Red Colobus and Red-tailed Monkeys at Ngogo, Kibale National Park, Uganda

Colobines often associate with cercopithecines at various African sites. Such polyspecific associations presumably have an antipredation function. At Ngogo, Kibale National Park, Uganda, red colobus (Procolobus rufomitratus) spend considerable time in association with red-tailed monkeys (Cercopithecus ascanius), and they are also heavily hunted by chimpanzees (Pan troglodytes). I conducted behavioral observations and playback experiments to test the hypothesis that red colobus and red-tailed monkeys obtain mutual protection and predator-related benefits by associating. Despite high chimpanzee hunting pressure on red colobus and much lower hunting pressure on red-tailed monkeys, red-tailed monkeys initiate, maintain, and terminate the associations. The results suggest that rather than providing red colobus with protection against chimpanzees, the associations occur mostly because they protect red-tailed monkeys against predation by eagles.

Hunting of Mammalian Prey by Budongo Forest Chimpanzees

Chimpanzee (Pan troglodytes) predation has been found in communities across Africa. Little evidence of such behaviour has been previously reported from the Budongo Forest, western Uganda. Here we present preliminary observations of predatory behaviour for the Sonso community, collected between August 1994 and February 2002. We find that the Sonso chimpanzees do not appear to hunt frequently, despite a relatively high density of potential prey, particularly Colobus guereza and Cercopithecus mitis. They seem similar to other eastern chimpanzees in their focus on immature colobus monkeys and in targeting ungulates, and the absence of red colobus (Procolobus badius) - the most common prey species elsewhere for chimpanzees - may be a significant factor.

Chimpanzee Predation and the Ecology of Microbial Exchange

Chimpanzee Predation and the Ecology of Microbial Exchange

Chimpanzee Predation and the Ecology of Microbial Exchange

Hunting provides one mechanism for the transmission of microbes across host species boundaries. It has generally been assumed that this mechanism leads to unidirectional transmission to humans. We report that wild chimpanzees occasionally prey on human children. This result and other evidence of chimpanzee hunting show the need for consideration of more complex predation-mediated host networks. Keywords: ecology, predation, Pan troglodytes , cross-species transmission, HIV, ebola, monkeypox, hunting, pathogen exchange.

Demographic influences on the hunting behavior of chimpanzees.

We investigated hunting in an unusually large community of wild chimpanzees at Ngogo in the Kibale National Park, Uganda. Aspects of predation were recorded with respect to the prey, the predators, and hunting episodes. During 23 months of observation, the Ngogo chimpanzees caught 128 prey items from four primate and three ungulate species. Chimpanzees preyed selectively on immature red colobus primarily during group hunts, with adult males making the majority of kills. Party size and composition were significant predictors of the probability that chimpanzees would hunt and of their success during attempts. Chimpanzees were more likely to hunt red colobus if party size and the number of male hunters were large; party size and the number of male hunters were also significantly larger in successful compared with unsuccessful hunts. The Ngogo chimpanzees did not appear to hunt cooperatively, but reciprocal meat-sharing typically took place after kills. Hunts occurred throughout the year, though there was some seasonality as displayed by periodic hunting binges. The extremely high success rate and large number of kills made per successful hunt are the two most striking aspects of predation by the Ngogo chimpanzees. We compare currently available observations of chimpanzee hunting behavior across study sites and conclude that the large size of the Ngogo community contributes to their extraordinary hunting success. Demographic differences between groups are likely to contribute to other patterns of interpopulation variation in chimpanzee predation.

<Article> First Observed Case of Chimpanzee Predation on Yellow Baboons (Papio cynocephalus) at the Mahale Mountains National Park.

<Article> First Observed Case of Chimpanzee Predation on Yellow Baboons (Papio cynocephalus) at the Mahale Mountains National Park.

The influence of chimpanzee predation on group size and anti-predator behaviour in red colobus monkeys

The extent to which predation influences the grouping patterns and behavioural ecology of non-human primates is a matter of continuing debate, but there are few field studies in which predation has been observed frequently enough to test the hypothesis that predation is an important influence. Group size and anti-predator behaviour of red colobus monkeys, Colobus badius tephrosceles, were studied in relation to predation by chimpanzees, Pan troglodytes schweinfurthii, in Gombe National Park, Tanzania. Predation by Gombe chimpanzees had a major impact on red colobus group size and structure. Mean group size of red colobus living in the core hunting area of their chimpanzee predators was 46% smaller than the mean size of groups living in the periphery of the chimpanzees' hunting range. Chimpanzees fed mainly upon immature red colobus monkeys at Gombe, and predation by chimpanzees was the likely limiting factor on red colobus group size and population size. Despite high levels of predation, there were few differences between large and small groups in likely predator avoidance behaviour: foraging and resting height, or nearest-neighbour proximity, for any age/sex class when they were not in the proximity of chimpanzees. When parties of chimpanzees were present the spatial positioning of colobus changed; females and immatures increased their nearest-neighbour scores to adult males, and adult males decreased their nearest-neighbour distances as a part of their communal defence tactics. Predation by chimpanzees elicits different detection and defence strategies from red colobus than do aerial (raptors) or terrestrial (felids) ambush predators. This appears to be owing to the social nature of chimpanzee hunting and the effect of chimpanzee party size and composition on hunting success.

The influence of chimpanzee predation on group size and anti-predator behaviour in red colobus monkeys

The influence of chimpanzee predation on group size and anti-predator behaviour in red colobus monkeys

Rates of predation on mammals by gombe chimpanzees, 1972–1975

Rates of chimpanzee predation on mammals are calculated using data on 75 kills recorded during focal observation in Gombe National Park, Tanzania, from January 1972 to April 1975. The chimpanzees were members of two study communities (Kanyawara, or Northern, and Kahama, or Southern, community), and were observed as focal individuals for 14,583 hr by more than 30 researchers and field assistants working in pairs. The rate of predation by females was too low to allow reasonable estimates. For males, the mean rate of killing during the study period was 0.31 kills per male per 100 hr (N=17 males), or 4.65 kills per 100 hr in the two communities. In contrast to results from Mahale Mountains, there was no difference in predation rate between wet and dry seasons. However, predation rates varied over time, increasing by four times between the first three and last four seasons of the sample period. In an average year the 15 adult and subadult male chimpanzees are calculated to have killed 204 prey per year in an area of 16 km2, varying between 99 and 420 prey per year in periods of low and high predation rate. Red colobus were the most frequent prey, followed by bushpig and bushbuck. Predation rates varied greatly on different prey species, and were not related to either the proportion of time spent within 200 m of male chimpanzees, or to their population densities. In relation to encounter rates and population density, baboons, blue monkeys, and redtail monkeys were killed at a fraction of the rate of red colobus monkeys, which suffered severe mortality from chimpanzee predation. Predation on bushpig and bushbuck also appears to have been high in relation to population density. The amount of food provided by predation is estimated to have averaged 600 kg per year for chimpanzees in the two communities (totalling 14–17 adult or subadult males, 18–20 adult of subadult females, and about 19 infants or juveniles). This suggests that adult males consumed around 25 kg of meat per year, although any average figure undoubtedly masks considerable individual variation. Present data suggest that chimpanzees in Gombe and Tai National Park, Ivory Coast, prey on mammals at rates higher than other populations.

Chimpanzee predation in the Mahale mountains from August 1979 to May 1982

Fifty-four episodes of predatory behavior of wild chimpanzees were recorded in Mahale, western Tanzania, from August 1979 to May 1982. The chimpanzees most frequently hunt in two seasons, during May, and from August to December. Longer-term fecal analysis indicates that predation frequency is significantly higher in the dry than in the rainy season. The seasonality of predation might be the result of the sum of various ecological factors, at least one of which is the birth season of the prey species. Most of the prey are juvenile blue duiker, bushbuck, bushpig, red colobus, and red-tailed monkeys. Sex difference is recognized in the prey selection and in the hunting method employed. Apparent local difference in the predatory behavior between Mahale and Combe chimpanzees (in Mahale,females hunt more frequently, and blue duiker is the most frequent prey) can be understood in terms of the difference either in the observation methods or in the faunal diversity and density. Other aspects of predatory behavior also are reported.

Chimpanzee Predation as a Possible Factor in the Evolution of Red Colobus Monkey Social Organization

Chimpanzee Predation as a Possible Factor in the Evolution of Red Colobus Monkey Social Organization