Evidence for delta Zn-66 values as indicators of meat consumption in the Tai chimpanzees
Résumé
The stable isotope ratios of Zn (δ66Zn) have been closely linked to trophic position (herbivore, omnivore, and carnivore) in a variety of animal species, with the potential to use δ66Zn values to indicate breastfeeding. In Taï National Park, Côte d’Ivoire, previous studies on dietary intakes from hunting resulted in contradictory interpretations of how infrequent meat consumption is reflected in light stable isotopes. Therefore, it remains unclear if infrequent meat consumption will be reflected in the δ66Zn values of a mainly frugivorous primate, such as the chimpanzee (Pan troglodytes). First, we examine if δ66Zn values could be a reliable indicator of trophic enrichment due to meat consumption in adult and adolescent chimpanzees (n = 26) where there is observed hunting and meat eating. Second, we test if the Zn isotopes of subadult chimpanzees (n = 7) fractionate relative to the ratios recorded for their respective mothers (n = 6) indicating nursing. We analyzed δ66Zn values in chimpanzee dental enamel samples from the Taï Chimpanzee Collection via MC-ICP-MS. We found that male chimpanzees, known to consume more meat than their female counterparts, are significantly lower in δ66Zn values relative to females, suggesting trophic enrichment. Subsequently, in δ66Zn values, breastfeeding chimpanzees (n = 3) were marginally higher, whereas in-utero chimpanzees (n = 4) were indistinguishable relative to their respective mothers. We suggest that δ66Zn analysis has the potential to indicate infrequent meat consumption in wild primates, with likely less interference from environmental factors than other isotope systems within the food web.
