Thursday, August 9, 2007: 10:10 AM
Blrm Salon III, San Jose Marriott
The development of successful foraging and migratory patterns in naïve animals is key to survival and can strongly influence a species’ range and dispersal. To investigate the development of these behaviours, we deployed Argos satellite tags on 12 male and 12 female young of year (YOY) grey seals on Sable Island, Nova Scotia. YOY were 5 mo old when tagged and deployments lasted 5-9 months. In addition, tracks from nearly 100 adult animals were available and had previously been analyzed for comparison. For this analysis, we fit a 2-state correlated random walk model in a state-space model (SSM) framework to estimate true locations from error prone Argos data and infer the animals’ behavioural state (foraging or directed motion) at each location. SSM approaches allow flexibility in model fitting by explicitly modeling measurement error and stochastic behavioral processes separately. For all individuals, the SSM inferred two distinct behavioural states. Locations inferred as “foraging” were generally over shallow banks, while locations in deep areas adjacent to banks were almost exclusively inferred as directed motion. Unlike adults, YOY had much smaller sexual differences in movement and foraging behaviour, had a more temporally uniform movement and foraging behaviour though the year, and forage much nearer to haulout locations. Additionally, some banks utilized heavily by YOY are rarely used by adults, suggesting YOY exploit different food resources than adults. Finally, YOY engaged in exploratory directed motion (inferred directed motion with no distinct foraging area at the terminus) more frequently than adults. These exploratory trips are slightly more frequent during the first half of their deployments than in the second half. Our results suggest YOY grey seals occupy a somewhat different ecological niche than adults, and continue to develop foraging strategy into their second year of life.
