Stable isotope evidence of meat eating and hunting specialization in adult male chimpanzees

Abstract

Observations of hunting and meat eating in our closest living relatives, chimpanzees (Pan troglodytes), suggest that among primates, regular inclusion of meat in the diet is not a characteristic unique to Homo. Wild chimpanzees are known to consume vertebrate meat, but its actual dietary contribution is, depending on the study population, often either unknown or minimal. Constraints on continual direct observation throughout the entire hunting season mean that behavioral observations are limited in their ability to accurately quantify meat consumption. Here we present direct stable isotope evidence supporting behavioral observations of frequent meat eating among wild adult male chimpanzees (Pan troglodytes verus) in Taï National Park, Côte d'Ivoire. Meat eating among some of the male chimpanzees is significant enough to result in a marked isotope signal detectable on a short-term basis in their hair keratin and long-term in their bone collagen. Although both adult males and females and juveniles derive their dietary protein largely from daily fruit and seasonal nut consumption, our data indicate that some adult males also derive a large amount of dietary protein from hunted meat. Our results reinforce behavioral observations of male-dominated hunting and meat eating in adult Taï chimpanzees, suggesting that sex differences in food acquisition and consumption may have persisted throughout hominin evolution, rather than being a recent development in the human lineage.dietary ecology | stable isotope analysis | human evolution C omparisons with extant primates and other mammals are essential to understanding the varied ecological niches occupied by early hominins. Data from chimpanzees (Pan troglodytes) indicate that populations living in different forest habitats have different food repertoires (1-4). Variation in hunting behavior and meat consumption has been observed between populations, with chimpanzee communities acquiring and consuming meat with varying levels of importance, from those who hunt rarely and largely opportunistically for slow-moving small mammals (4) to more regular, systematic hunting of medium-sized prey (2, 3, 5). As all chimpanzee populations rely heavily on various plants, nuts, and invertebrates for their daily energy requirements, the disparity in vertebrate meat consumption across populations has led some researchers (6, 7) to suggest that meat is an occasionally consumed, nonessential dietary supplement.The chimpanzees (Pan troglodytes verus) of the Taï National Park, Côte d'Ivoire, are known to be some of the most specialized chimpanzee hunters, consuming large quantities of meat annually, predominantly from Western red colobus (Procolobus badius) and, occasionally, Western black-and-white colobus (Colobus polykomos) monkeys (3,8). Hunting at Taï is cooperative among the male chimpanzees, and after capture, division of the resultant prey rewards participation in the hunt, rather than nepotism (2, 8). A significant adult male sex bias is also evident, with adult males reported to consum...

Comparative isotope ecology of African great apes

“…To assess model stability we re-ran each model on reduced datasets excluding levels of random effects, one at a time, compared the results of these models with the full model and found no evidence for influential fruit species. Long-term observations on the Taï population confirmed the sex-differentiated pattern in 15 N to be related to higher meat consumption frequencies in males (Fahy et al, 2013).…”

“…This conclusion is not supported by behavioral data which suggested that Taï males eat meat frequently (Fahy et al, 2013) whereas it is a much more rarely observed behavior in the bonobos from Salonga forest (Hohmann and Fruth, 1993;Surbeck et al, 2009). It also contradicts the interpretation of a previous dataset on the bonobos from Salonga forest which suggested the bonobo 15 N values to not exhibit significant levels of faunivory (Oelze et al, 2011).…”

“…Here, male chimpanzees had significantly 7 higher mean 15 N values than females as they consumed meat more frequently. Males observed to be successful hunters revealed the highest 15 N values in the community (Fahy et al, 2013).…”

“…The differentiation into separate or overlapping ecological niches can be assessed in sympatric primate species 4 (Schoeninger et al, 1998;Macho and Lee-Thorp, 2014;Oelze et al, 2014). Stable isotope analysis in hair keratin is a particularly useful approach when investigating temporal and inter-and intra-individual dietary variation in great apes (Oelze et al, 2011(Oelze et al, , 2014Fahy et al, 2013). The key advantages are that a hair strand records the dietary signature of a single individual over a long time period (several subsequent months) and hair isotopic data obtained from different individuals and species can be compared (Schwertl et al, 2005;Cerling et al, 2009;Oelze et al, 2011Oelze et al, , 2014.…”

A combined dietary approach using isotope and dental buccal-microwear analysis of human remains from the Neolithic, Roman and Medieval periods from the archaeological site of Tossal de les Basses (Alicante, Spain)

“…Parallel to this, the δ 15 N stable isotope ratio increases by 3-5‰ up the food-chain with each trophic level, and is usually used to indicate the position of an organism in the food chain (Minagawa and Wada, 1984). Based on the exact values of the nitrogen ratio, it is potentially possible to differentiate between individuals that consumed more animal resources from those who consumed very little animal proteins (Fahy et al, 2013), even if this quantification is less straightforward than previously thought (Hedges and Reynard, 2007). Furthermore, the fact that aquatic food chains tend to contain more trophic levels than terrestrial ones helps carbon isotope ratios to discriminate between the consumption of marine or C 4 terrestrial foods when samples are 13 C enriched (Schoeninger and De Niro, 1984).…”