Gastrointestinal bacteria play a pivotal role during digestion. Without these bacteria, an animal is unable to extract sufficient nutrients from its food. In highly variable environments, it is crucial that the gut bacteria responsible for breaking down food can react to rapidly changing diets and maintain their digestive role. The PIs in this project first examine these bacteria in a wild population of primates in Madagascar to understand their composition across seasonal environments. These results will be compared with those from captive primates to first, illuminate the impact a captive diet has on gastrointestinal bacteria, and second, aid in the creation of a more appropriate diet for captive animals, based on the metabolic capabilities of their gastrointestinal bacteria. Results can also translate to executable conservation action by informing the identification of suitable habitat reserves, based on the digestibility of the plants within, considering endangered animals and shrinking forests. Expanding lemur reserves to contain plants with a compatible chemical profile to these animals' bacterial capabilities will aid the survival and success of these flagship species.
The effect of variable diets on gut bacteria has only begun to be measured, and real-world studies on wild populations are lacking. This research focuses on wild sympatric populations of a generalist herbivore, the ring-tailed lemur (Lemur catta), and a specialist herbivore, Verreaux's sifaka (Propithecus verreauxi), in the seasonal forest of Beza Mahafaly Special Reserve, Madagascar. The composition of the diet of these lemurs is measured in conjunction with behavioral observations of feeding and chemical analysis for cellulose and phenolic content of the foods consumed. Gut bacteria in freshly collected lemur feces are measured using fluorescent in situ hybridization (FISH). All measurements occur across both the wet and dry seasons to track the changes in gut bacteria and ingested cellulose and phenolics as the foods available in the forest change seasonally. Results from the wild lemurs will be compared with those from captive lemurs.
This research project focused on characterizing the gut microbial communities in two wild species of lemurs, the ring-tailed lemur (Lemur catta) and Verreaux’s sifaka (Propithecus verreauxi). In addition to describing the gut microbial variation between these lemur species, between groups within each lemur species, across individuals within each lemur group, and across time within each lemur individual, this project also investigated the influence of diet on these communities. In particular, we looked at how a change in diet affected the gut microbial abundance and distribution. We focused on two types of dietary chemicals, cellulose (indigestible fiber) and polyphenols (a digestibility-reducing compound), found in the lemurs’ plant foods. We found that the Verreaux’s sifakas consumed increasing amounts of polyphenols in the wet season versus the dry season, whereas the ring-tailed lemurs consumed very low levels of polyphenols across both seasons. For cellulose consumption, we saw a lot of fluctuation across both seasons in both lemur species, with a rise in consumption at the end of the wet season. Along with this temporal variation, we saw higher cellulose consumption in the eastern-most groups of both the ring-tailed lemurs and Verreaux’s sifaka, whom live in a lusher gallery forest along a river running past the border of their territory. The knowledge gained from this research will add to our understanding of gut microbial ecology. These findings can be applied to human health to better understand the relationship between human diets and our own gut microbial communities. A healthy gut microbial community is vital to a healthy host, so knowing which diets help to maintain this community and which disrupt it can be incredibly useful in healthcare. The understanding of wild lemur gut microbiomes can also be applied to managing captive lemur populations. By comparing the gut microbes of captive and wild lemurs, we can better understand the digestive capabilities of captive lemurs and refine their diets to match the foods able to be digested by their guts. Alternatively, sick captive lemurs could be diagnosed with an unhealthy gut microbial community and inoculated with microbes from a healthier lemur to improve its health. Additionally, this research project had beneficial effects in the local community around the field site in Madagascar, with the employment of local field guides, positive interactions with local villagers and park staff, and the support of a Malagasy masters-level student in his research.
