Stable Carbon Isotope Values of Pan troglodytes Hair Correspond With Mean Annual Precipitation, but not Temperature, across Western Tanzanian Chimpanzee Study Sites.

Diet influences stable carbon and nitrogen stable isotope values (δ13C and δ15N values) in animal tissues; and here we explore the influences of the local ecology on those values in six separate troops of chimpanzees (Pan troglodytes). In this study we build upon Schoeninger et al.’s 2016 paper by exploring the influence of environmental factors by comparing three separate chimpanzee sites within Gombe Park to another three separate sites in neighboring Ugalla Park. We present new δ13C and δ15N values by using hairs collected from night nests in the 90’s and early 2000’s from Gombe and Ugalla. We then compare these new chimpanzee δ13Chair and δ15Nhair values to local Mean Annual Precipitation (MAP), Mean Annual Temperature (MAT), and the relationship between MAP and MAT. We used these comparisons to test hypotheses based on known effects of these variables on the δ13C and δ15N values in plant tissues that may be consumed by the chimpanzees. The comparisons show that hair from chimpanzees living in sites with lower MAP have higher δ13Chair and δ15Nhair values than do chimpanzees living in sites with higher MAP. Neither δ13Chair or δ15Nhair were significantly related to MAT, however, the relationship between MAP and MAT was seen to be significant. These results suggest the potential of using δ13C and δ15N values in primate tissues to infer attributes of their local ecology in circumstances where ecology may be unknown, such as samples collected in the last few hundred years or fossil hominins