Non-invasive genetic monitoring reveals spatiotemporal variation in social, demographic and genetic structure Arjen de Groot1, Hugh Jansman1, Dennis Lammertsma1, Hans-Peter Koelewijn12 & Loek Kuiters1 1 Animal Ecology, Alterra – Wageningen UR, Wageningen, The Netherlands 2 Nunhems B.V., Haelen, The Netherlands Our knowledge of the dynamics of natural wildlife populations is still limited, for various reasons. Demographic and genetic structure are strongly affected by fluctuating circumstances, as well as by social interactions among individuals. Understanding the interplay between social, demographic and genetic structure therefore requires simultaneous monitoring of each of these aspects over long time periods. Yet, traditional study methods are often hampered by practical constraints: individuals may be hard to recognize or track in the field, and methods may cause unwanted disturbances. Genetic profiling of non-invasively collected samples (e.g. faeces, hairs) can be a solution, as besides population genetic data it also yields data on population size, survival, reproductive success, mating patterns and spatial distribution. Since 2002, we applied non-invasive genetic monitoring to study a reintroduced population of Eurasian otters (Lutra lutra). Based on yearly collection of faecal samples, we were able to build a pedigree of the population, and to locate territories of individual animals. Here, we will show how this helped us to learn how social interactions, such as male dominance, may result in skewed survival and mating success, and how this affects the genetic viability of the population. We could show that levels of relatedness and inbreeding are rapidly increasing, even though genetic diversity and heterozygosity are still fairly high. This type of monitoring is essential for early detection of inbreeding risks, and may also shed new light on natural mechanisms for inbreeding prevention in mustelids.