Hooded seals (Cystophora cristata) in the Northwest Atlantic Ocean: Uncovering movement patterns, habitat selection and diving behaviour throughout the annual migration

Andersen, Julie M. (2014) Hooded seals (Cystophora cristata) in the Northwest Atlantic Ocean: Uncovering movement patterns, habitat selection and diving behaviour throughout the annual migration. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

How animals change their movement patterns in response to their environment is a central topic in ecology. The northwest (NW) Atlantic hooded seals occupy areas on the borderline between the North Atlantic- and high Arctic Ocean. By investigating these large predators’ movement patterns through the marine landscape, we can obtain a better understanding of the seasonal dynamics of habitat selection and use. This will improve the knowledge needed for good ecosystem management of critical habitat. This is especially important for highly vulnerable regions increasingly exposed to the oil and shipping industry, as well as global warming. NW Atlantic hooded seals rely on ice for two months of the year, when they reproduce and moult (March and July). Factors that influence the distribution at other times of the year are unknown. Here, 67 hooded seals (33 females, 18 males and 16 juveniles) were equipped with Satellite Relay Data Loggers (SRDLs) during the breeding or moulting season in the period 2004-2008. The study revealed that seals used areas of high topographic relief during migration. Such areas include the Labrador shelf, Davis Strait and Baffin Bay during the post-moult/pre-breeding period (August-February) and the area off the Grand Banks of Newfoundland, Flemish Cap, the Gulf of St. Lawrence and the southeast Greenland shelf during the post-breeding/pre-moult period (April-June). They exhibit sexual and age related segregation in terms of environmental habitat variables (sea surface temperature, surface chlorophyll concentration, bottom depth, bottom topography and ice concentration) and first passage time (FPT) at the area restricted search (ARS) scale. Furthermore, males and females demonstrated differences in diving strategies and fluctuations in the relative change of buoyancy over time. Females used areas with greater water depths than males and displayed an off-shelf, dynamic habitat use while males spent more time on top of the shelf and in areas of high topographic relief. I suggest that hooded seals exhibit a resource partitioning strategy to avoid competition between sexes, or that the geographic segregation and different patterns of timing and magnitude of lipid energy acquisition reflect a difference in energy requirements in relation to fasting periods.

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