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Larger body size leads to greater female beluga whale ovarian reproductive activity at the southern periphery of their range
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  • Steven Ferguson,
  • David Yurkowski,
  • Justine Hudson,
  • Tera Edkins,
  • Cornelia Willing,
  • Cortney Watt
Steven Ferguson
Fisheries and Oceans Canada
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David Yurkowski
Fisheries and Oceans Canada
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Justine Hudson
Fisheries and Oceans Canada
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Tera Edkins
Fisheries and Oceans Canada
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Cornelia Willing
Fisheries and Oceans Canada
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Cortney Watt
Fisheries and Oceans Canada
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Abstract

Identification of phenotypic characteristics in reproductively successful individuals provides important insights into the evolutionary processes that cause range shifts due to environmental change. Female beluga whales (Delphinapterus leucas) from the Baffin Bay region (BB) of the Canadian Arctic in the core area of the species’ geographic range have larger body size than their conspecifics at the southern range periphery in Hudson Bay (HB). We investigated the mechanism for this north and south divergence as it relates to ovarian reproductive activity (ORA = total corpora) that combines morphometric data with ovarian corpora counted from female reproductive tracts. Based on the previous finding of reproductive senescence in older HB females, but not for BB whales, we compared ORA patterns of the two populations with age and body length. Female beluga whale ORA increased more quickly with age (63% partial variation explained) in BB than in HB (41%). In contrast, body length in HB female beluga whales accounted for considerably more of the total variation (12 vs 1%) in ORA compared to BB whales. We speculate that female HB beluga whale ORA was more strongly linked with body length due to higher population density resulting in food competition that favors the energetic advantages of larger body size during seasonal food limitations. Understanding the evolutionary mechanism of how ORA varies across a species’ range will assist conservation efforts in anticipating and mitigating future challenges associated with a warming planet.

Peer review status:UNDER REVIEW

30 Jun 2021Submitted to Ecology and Evolution
01 Jul 2021Assigned to Editor
01 Jul 2021Submission Checks Completed
11 Jul 2021Reviewer(s) Assigned
11 Sep 2021Review(s) Completed, Editorial Evaluation Pending