A sheep’s gut is a battlefield where bacteria, parasites, and the animal’s own immune system fight for control—and the outcome determines whether the sheep lives long enough to reproduce. This matters because ecologists have long known that parasites harm wild animals and gut bacteria help them, but no one has tracked both simultaneously in a natural population. The Soay sheep of St Kilda offer a rare opportunity: every individual’s genetics, diet, reproductive history, and faecal samples have been recorded for decades. By applying next-generation DNA sequencing to those samples, the team will map how gut bacteria, protozoans, and nematodes shift over time, and how those shifts affect the sheep’s health and survival. This is fundamental science. It asks how an animal’s internal ecosystem—its “ecology within”—drives its fate in the wild. There is no immediate practical application. But understanding how gut communities shape host fitness in nature could eventually inform wildlife disease management, conservation strategies, or even reveal general principles about how within-host ecosystems evolve—insights that might one day translate to human or livestock health.
View original technical description
Individual animals are typically home to a staggeringly complex community of smaller organisms. This observation has led researchers to consider individuals as ecosystems in their own right, challenging us to think in new ways about how ecological processes may drive variation in an individual's health and fitness. The gut is rapidly emerging as an important example of how such within-individual ecosystems might interface with host physiology and health. In vertebrates, the gut is home not only to trillions of 'friendly' bacteria (the 'microbiota'), which have an essential role in extracting nutrition from food consumed, but also to diverse communities of parasites, which compete with their host for resources and can cause serious illness. The potential significance of this gut ecosystem for our understanding of the ecological and evolutionary dynamics of wild animal populations is immense. However, our current understanding of the drivers of gut ecosystem dynamics and their consequences for host fitness in natural populations is very limited. The application of new next-generation sequencing methods to faecal samples represents a potentially transformative approach to non-invasively monitor gut community dynamics and diet in wild animals. This approach has already revolutionised our understanding of the human gut bacteria community and its role in health and disease, but has yet to be applied to wild study systems in which individual genotype, diet, immunity and fitness are all closely monitored. This project will apply this approach to faecal samples collected longitudinally from an exceptionally well-studied wild mammal population to simultaneously monitor variation in gut bacteria, protozoan and nematode communities and diet. This will allow us to address fundamental outstanding questions about which factors drive gut community dynamics within individuals and the outcomes of these dynamics for health and fitness under natural conditions. Our study system, the Soay sheep of St Kilda, will allow us to regularly and repeatedly sample known individuals with well-characterised genetics, environmental experiences and reproductive history. Our project will also involve the development and application of a novel statistical approach to integrate data on gut community ecology with our understanding of host ecology and genetics, and new ecological and epidemiological models that will transform our understanding of how the gut ecosystem impacts on host population and disease dynamics in nature. Our project will provide the first integrated study mapping the relationships between gut commensal and parasite communities, host diet, immunity and fitness in the wild. Our findings will profoundly improve our understanding of the significance of within-host ecosystem across a broad range of ecological disciplines within NERC's remit, including population, community, disease and evolutionary ecology.
Plain English summaries and category classifications on this site are generated by AI and may not perfectly reflect the original research.
Is something wrong? Let us know