Faecal n-alkanes differ significantly between two lemur species reflecting differences in consumed diet

Gemma Baker , James Bendle, Lydia K. Greene, Kweku Afrifa Yamoah, Matthew Allison , Sarah E Greene 

The diet of an animal reflects its species’ ecology and local food availability and is often a key metric for monitoring the health and welfare of endangered species. However, determining diets across individuals and through space and time, is an inherent challenge within ecology, being expensive and time-intensive to accomplish with observations. Faeces offer the opportunity for non-invasive sample collection and can provide a snapshot of the ingested diet of the producer. In modern ecology, faecal samples have been a prime target for genetic analyses of diet and the gut microbiome. Here, however, we explore the efficacy of using high molecular weight (HMW) n-alkane biomarkers extracted from faeces as dietary tracers. HMW n-alkanes are commonly employed in palaeoecological reconstructions. Combining faecal HMW n-alkane analyses with gut microbiome composition and detailed foraging data applied to two species of lemur in captivity with access to naturalized forest enclosures, we assess the potential of HMW n-alkane profiling in dietary analyses, and therefore modern ecology. Recovered HMW n-alkanes are completely dietary in origin and not degraded or influenced by the gut microbiome. Signatures are significantly different between focal lemur species and seasons, reflecting differences in ingested diet. It is possible to infer changes in the relative contributions of major food types, like leaves and fruits, based on the faecal HMW n-alkane concentrations. The potential applications for these methods in both captive and wild lemur populations, other primates, and other herbivorous and omnivorous animals are wide and varied. HMW n-alkanes are simple to identify and measure; only requiring commonly available and relatively affordable analytical chemistry instruments (e.g. GC-FID). These analyses could open a wide array of modern ecological research possibilities with further research and ground truthing.