Research scientist Fisheries and Oceans Canada, Quebec, Canada
Individual specialization has long been ignored when estimating population adaptability to a changing environment. However, variability in diet selection among conspecifics could be key for insuring population persistence. Increasing human and climatic perturbations have impacted the quality and availability of food resources and habitat for marine predators, including marine mammals. Here, we focus on the endangered St. Lawrence Estuary beluga (Québec, Canada), a population which has experienced major changes in their environment due to overfishing, increase in population size of potentially competing species, and global warming. We examine and quantify long-term changes in beluga diet and degree of specialization at both the individual and population levels using stable isotopes. Results indicate that the population, which was mainly composed of intermediate generalist or specialist individuals in the 1990s and early 2000s, has seen a progressive increase of the proportion of “true” generalists over the past decade. They also highlight that several prey that were unimportant for this beluga population in the past, increased in importance since ~2008, leading to both a recent diversification of the diet and an increased heterogeneity in resource selection among conspecifics (variability in diet among individuals increased by >200%). Overall, these findings indicate that St. Lawrence Estuary beluga have widened their trophic niche in recent years, possibly to limit inter- and/or intra-specific competition for food resources.
