Abstract
Both body size dimorphism and sex differences in the relative costs and benefits associated with acquiring energy for reproduction have been advanced to explain the evolution of sex differences in foraging behaviour. We examined the extent to which these factors influenced sex differences in the diving behaviour of a size-dimorphic, capital breeder, the grey seal, Halichoerus grypus. Using time-depth data loggers, we examined the diving behaviour of 46 male and 49 female grey seals for 7 months before parturition and mating. Males and females showed significantly different seasonal patterns in the characteristics of individual dives and dive effort. Compared with males, females showed significantly higher levels of dive effort immediately following moult and in the 3 months before parturition. Females also had longer dives (5. 5 versus 4.9 min) and spent more time at depth (3.4 versus 2.7 min), whereas males dived deeper (57 versus 49 m). Males dived consistently throughout the day, whereas females showed strong diurnal patterns in dive depth, duration and frequency. The diving behaviour and rates of mass gain by females suggested a pattern of foraging consistent with early accumulation of body energy to support pregnancy and the subsequent lactation period during which females fast. Males, on the other hand, showed diving behaviour and rates of mass gain consistent with a more gradual accumulation of energy stores. Our results suggest that sex differences in the seasonal patterns of diving behaviour reflect sex differences in the costs and benefits of stored energy for reproduction rather than the influence of body size dimorphism alone.
| Original language | English |
|---|---|
| Pages (from-to) | 777-789 |
| Number of pages | 13 |
| Journal | Animal Behaviour |
| Volume | 66 |
| Issue number | 4 |
| DOIs | |
| Publication status | Published - Oct 2003 |
Bibliographical note
Funding Information:We thank Debbie Austin, Shawn Beaver, Brian Beck, Daryl Boness, Dave Coltman, Sara Ellis, Lucy Grypus, Shelley Lang, Damian Lidgard, Jo-Ann Mellish, Monica Mulbert, Wayne Stobo and Dan Tully for their assistance in the field. We also thank Gerry Forbes, Officer-in-Charge of the Atmospheric Environmental Service for logistical support on Sable Island. Wade Blanchard provided valuable advice on statistical analysis and the use of linear mixed effects models. Daryl Boness, Ian Boyd, Andy Horn, Marty Leonard, Ram Myers, Greg Thiemann and four anonymous referees provided comments on earlier drafts of the manuscript. This study was supported by a Natural Sciences and Engineering Research Council (NSERC), Canada, scholarship to C.A.B., by NSERC research grants to W.D.B. and S.J.I. and by the Department of Fisheries and Oceans, Canada. All procedures used on grey seals in
ASJC Scopus Subject Areas
- Ecology, Evolution, Behavior and Systematics
- Animal Science and Zoology