Intrinsic and extrinsic drivers of activity budgets in sympatric grey and harbour seals

Russell, D. J. F., McClintock, B. T., Matthiopoulos, J. , Thompson, P. M., Thompson, D., Hammond, P. S., Jones, E. L., MacKenzie, M. L., Moss, S. and McConnell, B. J. (2015) Intrinsic and extrinsic drivers of activity budgets in sympatric grey and harbour seals. Oikos, 124(11), pp. 1462-1472. (doi: 10.1111/oik.01810)

Full text not currently available from Enlighten.

Abstract

Investigation of activity budgets in relation to seasonal, intrinsic (age, sex) and extrinsic (time of day, spatial) covariates enables an understanding of how such covariates shape behavioural strategies. However, conducting such investigations in the wild is challenging, because of the required large sample size of individuals across the annual cycle, and difficulties in categorising behavioural states and analysing the resulting individual-referenced and serially correlated data. In this study, from telemetry tags deployed on 63 grey seals Halichoerus grypus and 126 harbour seals Phoca vitulina we used behavioural data, and movement data within a Bayesian state–space model (SSM), to define population-level activity budgets around Britain. Using generalised estimating equations (GEEs) we then examined how time spent in four states (resting on land (hauled out), resting at sea, foraging and travelling) was influenced by seasonal, intrinsic and extrinsic covariates. We present and discuss the following key findings. 1) We found no evidence that regional variation in foraging effort was linked to regional population trajectories in harbour seals. 2) Grey seals demonstrated sex-specific seasonal differences in their activity budgets, independent from those related to reproductive costs. 3) In these sympatric species there was evidence of temporal separation in time hauled out, but not in time foraging. 4) In both species, time spent resting at sea was separated into inshore (associated with tidal haul out availability) and offshore areas. Time spent resting at sea and on land was interchangeable to some extent, suggesting a degree of overlap in their functionality. This may result in a relaxation of the constraints associated with a central place foraging strategy. More generally, we demonstrate how a large dataset, incorporating differing tag parameters, can be analysed to define activity budgets and subsequently address important ecological questions.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Matthiopoulos, Professor Jason
Authors: Russell, D. J. F., McClintock, B. T., Matthiopoulos, J., Thompson, P. M., Thompson, D., Hammond, P. S., Jones, E. L., MacKenzie, M. L., Moss, S., and McConnell, B. J.
College/School:College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine
Journal Name:Oikos
Publisher:Wiley-Blackwell Publishing, Inc.
ISSN:0030-1299
ISSN (Online):1600-0706

University Staff: Request a correction | Enlighten Editors: Update this record