The feeding ecology of sympatric great ape species yields valuable information for palaeodietary reconstructions in sympatric early hominin species. However, no isotopic references on sympatrically living apes and their feeding ecology are currently available. Here we present the first isotopic study on sympatric great apes, namely western lowland gorillas (Gorilla gorilla gorilla) and central chimpanzees (Pan troglodytes troglodytes) from Loango National Park, Gabon. We successfully analyzed the stable carbon and nitrogen isotope ratios in a selection of food plants (n = 31) and hair samples (n = 30) retrieved from sleeping nests to test whether niche partitioning among sympatric chimpanzees and gorillas is detectable using isotope analysis of hair. Ape hair strands with roots were sectioned into sequential segments (n = 100) to investigate temporal isotopic variation related to seasonal variations in food resources. We found significant δ(13)C differences between herbaceous plants and fruits, most likely due to canopy effects. While the δ(13)C values of chimpanzees indicate the consumption of fruit, the low δ(13)C values in gorilla hair indicate folivory, most likely the consumption of (13)C-depleted herbaceous vegetation. Our isotopic data also confirmed dietary overlap between chimpanzees and gorillas, which varied by season. Gorillas showed significant variation in δ(13)C values in response to season due to shifting proportions of herbaceous plants versus fruits. In chimpanzees, significant seasonal variation in δ(15)N was likely related to the seasonal availability of fruit species with particularly high δ(15)N values. In summary, we found isotopic evidence for niche partitioning and seasonal dietary variation among sympatric great apes at Loango. These findings provide a valuable reference for palaeodietary research on fossil hominins using δ(13)C analyses, particularly for studies focusing on sympatric taxa and on temporal isotopic variation within incremental tissues such as tooth enamel.

In primates, age, sex, and social status can strongly influence access to food resources. In Pan, these criteria are assumed to influence access to vertebrate meat. However, the significance of meat in terms of its role in the nutrition of Pan is still debated. Here we present a study using stable carbon and nitrogen isotope ratios in hair samples from habituated, wild bonobos (Pan paniscus) to explore these issues. Over a period of 5 mo hair samples were collected from fresh bonobo nests at LuiKotale, Democratic Republic of Congo. Hair samples were assigned to known individuals and were of sufficient length to allow the evaluation of isotopic variation over several months. Samples of plant foods and sympatric fauna were also analyzed. The δ 13 C and δ 15N results of the bonobo hair were remarkably homogeneous over time and for the group as a whole. There are no differences in diet between the sexes. Within the group of males, however, there was a positive correlation between dominance status and δ 15 N. The isotopic data indicate that the contribution of fauna to bonobo diet is marginal and that plant food is the dietary protein source. In only some cases did elevated δ feeding ecology | great apes R econstructing hominin diets and possible meat-eating behavior is a key research area in the field of human evolution (1, 2) because adaptations for the consumption of animal protein and fat have been related to brain developmental trends in the evolution of the human lineage (3). As our closest living relatives, bonobos (Pan paniscus) and chimpanzees (Pan troglodytes) are often used as referential models in the context of diet composition, feeding behavior, and food processing (4, 5). The diet of both Pan species is dominated by plant foods: fruits account for more than 50% of the daily dietary intake and are complemented by leaves, herbs, and, at least in some populations, underground storage organs. Both species supplement their plant diet with insects and meat from vertebrates acquired by hunting (6). Behavioral observations from meat-eating events suggest that both Pan species consider meat a highly attractive food; meat is generally considered to be a high-quality food resource that offers nutrients that are difficult to obtain from other foods (7). Conflicts among those who compete for access to meat are frequent, and dominant individuals may take carcasses from subordinates. Longitudinal data from one population suggest that meat consumption by female chimpanzees can shorten interbirth intervals (8). Given the close link between the nutritional status of females and reproductive success, the inferred nutritional function of meat eating seems plausible, but requires further exploration. Although existing evidence demonstrates that meat is part of the diet of most or all Pan populations, how meat consumption relates to the overall diet remains unknown (7). Hunting and meat eating is less frequently observed in bonobos (Pan paniscus) compared with some chimpanzee populations (9). Observational data from two sit...

The Early Bronze Age necropolis of Singen (Hohentwiel), located near Lake Constance, represents a population from a period of technological transition in southwestern Germany. The site contains several graves with metal artefacts that originated in other parts of Central and Western Europe, and therefore these could be interpreted as being the graves of non-local individuals. The purpose of this study was to investigate this possibility through the application of isotopic analysis. The ratios of strontium and oxygen isotopes in human enamel reflect the geological origin of food and drinking water consumed during enamel formation in early life stages. Additionally, the ratio of sulphur isotopes from bone collagen reflects the origin of foods consumed during the last 10-20 years of life of an adult individual. We used these three isotope systems to attempt to identify local and non-local individuals at the site. We found that the isotope ratios of Sr, O and S of the humans were relatively homogeneous and generally correspond to the isotope signature of the local geology, climate and environment. We conclude that the sampled population is of local origin and does not show patterns of individual mobility, even though there is evidence for long-distance trade and exchange of the metal artefacts at this site.

A mounting body of evidence suggests that changes in energetic conditions like prolonged starvation can be monitored using stable isotope ratios of tissues such as bone, muscle, hair, and blood. However, it is unclear if urinary stable isotope ratios reflect a variation in energetic condition, especially if these changes in energetic condition are accompanied by shifts in dietary composition. In a feeding experiment conducted on captive bonobos (Pan paniscus), we monitored urinary δ(13)C, δ(15)N, total C (carbon), total N (nitrogen), and C/N ratios and compared these results with glucocorticoid levels under gradually changing energy availability and dietary composition. Measurements of daily collected urine samples over a period of 31 days showed that while shifts in urinary isotope signatures of δ(13)C and δ(15)N as well as total C were best explained by changes in energy consumption, urinary total N excretion as well as the C/N ratios matched the variation in dietary composition. Furthermore, when correcting for fluctuations in dietary composition, the isotope signatures of δ(13)C and δ(15)N as well as total C correlated with urinary glucocorticoid levels; however, the urinary total N and the C/N ratio did not. These results indicate for the first time that it is possible to non-invasively explore specific longitudinal records on animal energetic conditions and dietary compositions with urinary stable isotope ratios and elemental compositions, and this research provides a strong foundation for investigating how ecological factors and social dynamics affect feeding habits in wild animal populations such as primates.