Abstract:
Southern elephant seals (Mirounga leonina. are important predators in Southern Ocean food webs and are known to exhibit high levels of foraging site fidelity with occasional deviations. The relationship between environmental variables and the at-sea behaviour of southern elephant seals (SES. and the possible correlates of environmental cues with SES foraging fidelity remains poorly understood. This study aimed to assess the environmental drivers of changes in behaviour for individuals tracked over multiple foraging migrations and to analyse the relationship between a series of environmental variables and SES at-sea behaviour using linear mixed effects models. We report on behavioural data from 95 satellite relay data loggers (SRDLs. deployed on SES at Marion Island between April 2004 and September 2013. Individual-level variance accounted for substantial variance within the models, and few environmental variables were identified as strong predictors of behaviour. Male SES two-dimensional (2D. home range sizes were significantly correlated with seal age, encountered chlorophyll–a (chl-a. concentration and temperature at depth, possibly resulting from age-related diet differences in male SES. Seals travelling greater distances tended to target deeper waters, seals travelling shorter distances tended to target shallower areas during their migrations. Bathymetry was further significantly correlated with female SES direction and 2D home range size. Female SES tended to perform deeper, but shorter, dives if the previous year had high chl-a. Females also adjusted their 3-dimensional home range overlap according to the sea surface temperature (SST. from the current and previous year. The results show the potential usefulness of including time lags in the use of remotely sensed predictors (e.g. chlorophyll. to account for the time required for energy transfer through trophic levels. Many of the environmental variables did not consistently explain behaviour between sexes and repeated tracks, suggesting complexity in the physical drivers of SES at sea behaviour. - Abstract as displayed in the - Abstract booklet. The presentation on the day may differ from the - Abstract.
