Limited evidence of C4 plant consumption in mound building Macrotermes termites from savanna woodland chimpanzee sites

Abstract

Stable isotope analysis is an increasingly used molecular tool to reconstruct the diet and ecology of elusive primates such as unhabituated chimpanzees. The consumption of C4plant feeding termites by chimpanzees may partly explain the relatively high carbon isotope values reported for some chimpanzee communities. However, the modest availability of termite isotope data as well as the diversity and cryptic ecology of termites potentially consumed by chimpanzees obscures our ability to assess the plausibility of these termites as a C4resource. Here we report the carbon and nitrogen isotope values from 79Macrotermestermite samples from six savanna woodland chimpanzee research sites across equatorial Africa. Using mixing models, we estimated the proportion ofMacrotermesC4plant consumption across savanna woodland sites. Additionally, we tested for isotopic differences between termite colonies in different vegetation types and between the social castes within the same colony in a subset of 47 samples from 12 mounds. We found thatMacrotermescarbon isotope values were indistinguishable from those of C3plants. Only 5 to 15% ofMacrotermesdiets were comprised of C4plants across sites, suggesting that they cannot be considered a C4food resource substantially influencing the isotope signatures of consumers. In theMacrotermessubsample, vegetation type and caste were significantly correlated with termite carbon values, but not with nitrogen isotope values. LargeMacrotermessoldiers, preferentially consumed by chimpanzees, had comparably low carbon isotope values relative to other termite castes. We conclude thatMacrotermesconsumption is unlikely to result in high carbon isotope values in either extant chimpanzees or fossil hominins.