| dc.contributor.author | Beck, Charlotte Anne (Carrie). | en_US |
| dc.date.accessioned | 2014-10-21T12:33:46Z | |
| dc.date.available | 2002 | |
| dc.date.issued | 2002 | en_US |
| dc.identifier.other | AAINQ67647 | en_US |
| dc.identifier.uri | http://hdl.handle.net/10222/55821 | |
| dc.description | Sex differences in foraging ecology have been noted in a variety of taxa and are most commonly attributed to sexual size dimorphism, inter-specific competition, and the differing reproductive roles of males and females during the breeding season. More recently, sex differences in foraging behaviour have been linked to the differing trade-off solutions of the sexes that allow an individual's reproductive success to be maximized. Among marine carnivores, such as pinnipeds, sex differences in foraging ecology have been difficult to study due to the wide-ranging, at-sea nature of foraging outside of the breeding season and the fact that feeding often occurs at depth where direct observation is rarely possible. I examined sex differences in the foraging ecology of adult grey seals, Halichoerus grypus, in the Northwest Atlantic, over the 8-month period prior to breeding using of time-depth data-loggers and satellite telemetry to measure temporal and spatial scales of foraging, hydrogen isotope dilution methods to examine longitudinal changes in body composition and energy gain, and quantitative fatty acid signature analysis to estimate diet composition. The influence of seasonal changes in body composition and hence buoyancy on diving behaviour was also examined. | en_US |
| dc.description | Grey seals are size dimorphic, with males being 1.5 times larger than females; thus, sex-differences in foraging were expected given the higher absolute energy requirement of males. However, the sex-specific seasonal pattern of diving behaviour, found at multiple temporal scales (i.e., individual dives, bouts of diving and trips) indicated that females had a higher level of dive effort than males in the periods directly following the spring moult and in the 3-months directly prior to breeding. This suggests that males and females make different decisions about the allocation of time to foraging and other activities (e.g. resting at the surface) with females spending more time foraging than males. Sex differences in the seasonal pattern of energy storage mirrored these patterns in diving behavior with females accumulating stored body energy earlier in the pre-breeding foraging period than males. These results suggest that sex differences in the seasonal pattern of foraging likely reflect sex-specific decisions for dealing with the costs and benefits of storing energy for reproduction during the foraging period. During the mid-late 1990s, the diet of both males and females was dominated by capelin during the 3-months prior to breeding. However, diet composition differed significantly between sexes with females consuming a higher proportion of sandlance and a lower proportion of skates and squid relative to males. Among individuals foraging on the eastern Scotian Shelf, males had a more diverse but lower energy-density diet than did females. In combination with differences in diving behaviour, these differences in diet suggest that males are less selective than females and including more prey species of lower energy density in their diet to increase overall intake and meet the energy demands imposed by larger body size. Thus, both sexual size dimorphism and the sex differences in the costs and benefits of energy storage for reproduction appear to influence the foraging ecology of this species. | en_US |
| dc.description | Thesis (Ph.D.)--Dalhousie University (Canada), 2002. | en_US |
| dc.language | eng | en_US |
| dc.publisher | Dalhousie University | en_US |
| dc.publisher | | en_US |
| dc.subject | Biology, Ecology. | en_US |
| dc.subject | Biology, Oceanography. | en_US |
| dc.subject | Biology, Zoology. | en_US |
| dc.title | Sex differences in the foraging ecology of a size-dimorphic marine carnivore. | en_US |
| dc.type | text | en_US |
| dc.contributor.degree | Ph.D. | en_US |
