Life history variation in 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 seals. During the next five years, my students and I to plan build upon our long-term studies of life history and foraging ecology of grey seals (Halichoerus grypus). Variability in reproductive performance within and among individuals over their reproductive life has been documented for relatively few large long-lived vertebrates. Mean estimates of traits obscure potentially important variability in the response of individuals to environmental variability and trends. We plan to continue the collection of long-term data (>30 years in 2017) from >1700 individually marked, known-age females to investigate intrinsic and extrinsic sources of individual variability in reproductive performance and survival and to evaluate the consequences of this variability on offspring survival and size at weaning. These data will also be used to test for the nature of heterogeneity (fixed vs dynamic) in performance and the relationship between age at first birth and lifetime reproductive success. We will also use the sighting histories of permanently marked males (~600) and females (as above) to test hypotheses concerning sex-specific onset and rate of survival and reproductive senescence and how patterns of survival vary with changes in population abundance and environmental variability. Although offspring size is often used as a proxy for female and offspring fitness, this hypothesis has rarely been tested in large, long-lived (>20 yr) mammals. Size and other offspring traits were measured for about 2400 permanent-marked grey seals pups that were born from 1998 to 2002 and another 2100 pups from 2014 to 2016. We will measure size and age at recruitment of the survivors of those pups to test the relationship between offspring size, survival, and long-term reproductive performance. We will use fine-scale GPS tracks from grey seals fitted with two tri-axial accelerometers to develop algorithms to distinguish behaviours, including foraging, to validate behavioural states estimated from state-space movement models. Along with animal-borne cameras we seek to better understand the spatial and temporal pattern of foraging in an upper trophic-level marine predator.