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

• Published in: Oikos
• Main Authors: Russell, Deborah Jill Fraser, McClintock, Brett Thomas, Matthiopoulos, Jason, Thompson, Paul, Thompson, David, Hammond, Philip Steven, Jones, Esther Lane, MacKenzie, Monique, Moss, Simon, McConnell, Bernie J
• Other Authors: NERC, University of St Andrews.School of Biology, University of St Andrews.Marine Alliance for Science & Technology Scotland, University of St Andrews.Scottish Oceans Institute, University of St Andrews.Centre for Research into Ecological & Environmental Modelling, University of St Andrews.Sea Mammal Research Unit
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2016
• Subjects: Area-restricted search; Bayesian; Energetic requirements; Energy budget; Hidden process models; Pinnipeds; Time budget; GE Environmental Sciences; QH301 Biology; 3rd-NDAS; BEIS/DECC; NERC; GE; QH301; Phoca vitulina
• Online Access: https://hdl.handle.net/10023/8329; https://doi.org/10.1111/oik.01810

D. J. F. Russell was funded by the UK Department of Energy and Climate Change (DECC) as part of their Offshore Energy Strategic Environmental Assessment programme and by Scottish Government as part of their Marine Mammal Scientific Support Research Programme (MMSS/001/11). The telemetry tags and their deployment were funded by DECC, the Natural Environment Research Council, Scottish Government, Marine Scotland Science and The European Commission. 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 ...