Effects of maternal traits and individual behavior on the foraging strategies and provisioning rates of an income breeder, the Antarctic fur seal

Abstract

The ability of an animal to acquire energy will affect its allocation to offspring and will ultimately influence fitness. This study investigated the relative influence of maternal traits, seasonal demands of pup-rearing, and individual effects on the foraging behavior of 27 female Antarctic fur seals Arctocephalus gazella at Cape Shirreff, Livingston Island, Antarctica during 2 austral summers (2005 and 2006), using time depth recorders. The relationship between foraging and allocation was investigated using pup growth as an indicator of parental investment. While female diving behavior differed between years, trip duration was below the 10 yr mean and did not differ between the 2 years of the study, indicating favorable feeding conditions in both years. Study year and maternal age accounted for a significant amount of the variation in day and night dive characteristics, while maternal mass influenced only parameters related to night dive effort. As the season progressed, females increased their dive effort at night, made shorter daytime dives, with more bout diving. Indi- vidual variability accounted for a significant amount of the variation in all foraging parameters. Females could be assigned to one of 4 behavioral dive groups (high effort, low effort, intermediate effort with high dive rate, and intermediate effort), based on 13 dive parameters although year instru- mented and age appeared to be important in determining group affiliation. Age, mass, year, and trip number influenced diving behavior; however, there was no relationship between foraging behavior and pup growth rate, except in young females.