Fine scale foraging habitat selection by two diving central place foragers in the Northeast Atlantic

Abstract

1. Understanding the animal-habitat relationship at local scale is crucial in ecology, particularly to develop strategies for wildlife management and conservation. As this relationship is governed by environmental features and intra and inter-specific interactions, habitat selection of a population may vary locally between its core and edges. 2. This is particularly true for central place foragers, such as grey and harbour seals, whose trends in numbers vary among different regions in the Northeast Atlantic. Here, we aimed at studying how foraging habitat selection may vary locally with the influence of population trends and physical habitat features 3. Using GPS/GSM tags deployed in grey and harbour seal colonies of contrasting sizes, we investigate spatial patterns and foraging habitat selection by comparing trip characteristics and home range similarities, and fitting GAMM to the seal distribution and environmental data respectively. 4. We show that grey seal foraging habitat selection and spatial patterns differed markedly between regions. Grey seals may select environmental characteristics for their foraging habitat accounting for local differences in prey consumed. Spatial patterns were different might depend on local seal density and regional productivity, located from inshore to offshore areas for the limit ranges and core population respectively. Our results on foraging habitat selection reflected the coastal and sedentary behaviour of harbour seals. We found no difference in spatial patterns between colonies, except for the Inner Hebrides where seals foraged further, potentially reflecting density dependence pressure, as the number in this colony is higher. 5. These results suggest that local conditions might have a strong influence on population spatial ecology, highlighting as well the relevance of studying foraging habitat selection based on foraging behaviour at fine geographical scale, particularly if species are managed within regional units.