Premium
Effects of maternal age and mass on foraging behaviour and foraging success in the northern elephant seal
Author(s) -
Hassrick Jason L.,
Crocker Daniel E.,
Costa Daniel P.
Publication year - 2013
Publication title -
functional ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.272
H-Index - 154
eISSN - 1365-2435
pISSN - 0269-8463
DOI - 10.1111/1365-2435.12108
Subject(s) - foraging , biology , ecology , predation , fur seal
SummaryAnimals that show indeterminate growth and put relatively constant proportions of stored body reserves towards annual reproductive effort are confronted with a problem of meeting ever‐increasing energetic demands in unpredictable environments. We examined how intrinsic traits, mass and age, as well as extrinsic environmental features impact diving and movement behaviour in a marine capital breeder, the northern elephant seal, Mirounga angustirostris . We assessed the impact of this behavioural variation on foraging success, measured as energy gained at sea. We used principal component analysis to reduce behavioural variables into three principal components that described time in foraging zones ( PC 1), foraging distance ( PC 2) and bout structure of dive shapes ( PC 3). Both intrinsic traits and extrinsic environmental features influenced behaviour and foraging success. Body mass was the sole predictor of residence time in foraging zones ( PC 1), which, in turn, was the strongest behavioural predictor of foraging efficiency and success over the short postbreeding season. Foraging distance ( PC 2) significantly varied with year. Since foraging distance is an index of the horizontal and vertical distances seals travel while foraging, we suggest that it was impacted by inter‐annual variation in marine prey distribution. Age had a negligible impact on most aspects of behaviour, except for the structure of dive shapes on the postmoult foraging trip. All principal components significantly impacted rates of energy gain for postbreeding foraging trips when maternal body stores must be recovered quickly before returning to shore to moult. Age impacted the bout structure of dives in pregnant females in a way that influenced success, suggesting a role for previous experience during the long postmoult foraging migration. Strong impacts of body mass on diving ability, foraging success and reproductive effort suggest a proximate mechanism for trade‐offs in the cost of reproduction. Mass lost to current investment in offspring impacts a mother's ability to accrue resources for future offspring.