Ecology of pinnipeds

The long-term objective of my research is to understand the evolutionary and ecological factors that have shaped the foraging and reproductive strategies of pinnipeds. We have demonstrated broad differences in the ecology of adult male and female grey seals. Because many marine mammals and seabirds express size dimorphism similar to grey seals, the kind of sex-specific differences we have found in grey seals may be common. We have also demonstrated pronounced age-related differences in reproductive performance of female grey seals, including strong evidence of senescence. During the next five years, my students and I plan to study sources of variability in reproductive performance within and among grey seal females over time. We also plan to test hypotheses about the behavioural and physiological mechanisms that underlie the decline in reproductive performance of older females (i.e., those >30 yr old). Offspring size is often used as a proxy for female and offspring fitness in large mammals, but this hypothesis has rarely been tested in marine carnivores. We have data on size at weaning for samples of five cohorts and will use size and age at recruitment, early reproductive success. There is evidence that considerable individual variation in diet is obscured by averaging across individuals. We will use fatty acid signature analysis to examine the relative importance of within vs. among individual variation in diet and thus to better understand these components of dietary niche width. Finally I plan to investigate the ontogeny of foraging behaviour in grey seals using models fit to Argos satellite locations data. The results of this research have implications for the conservation and management of pinnipeds and for our understanding of the importance of top-down effects of large marine carnivores on ecosystem structure and functioning.