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A long post-reproductive lifespan is a shared trait among genetically distinct killer whale populations
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  • Mia Nielsen,
  • Samuel Ellis,
  • Jared Towers,
  • Thomas Doniol-Valcroze,
  • Daniel Franks,
  • Michael Cant,
  • Michael Weiss,
  • Rufus Johnstone,
  • Kenneth Balcomb III,
  • David Ellifrit,
  • Darren Croft
Mia Nielsen
University of Exeter
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Samuel Ellis
University of Exeter
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Jared Towers
Fisheries and Oceans Canada Pacific Region
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Thomas Doniol-Valcroze
Fisheries and Oceans Canada Pacific Region
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Daniel Franks
University of York
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Michael Cant
University of Exeter
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Michael Weiss
University of Exeter
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Rufus Johnstone
University of Cambridge
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Kenneth Balcomb III
Center for Whale Research
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David Ellifrit
Center for Whale Research
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Darren Croft
University of Exeter
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Abstract

The extended female post-reproductive lifespan found in humans and some toothed whales remains an evolutionary puzzle. Theory predicts demographic patterns resulting in increased female relatedness with age (kinship dynamics) can select for a prolonged post-reproductive lifespan due to the combined costs of inter-generational reproductive conflict and benefits of late-life helping. Here we test this prediction using >40 years of longitudinal demographic data from the sympatric yet genetically distinct killer whale ecotypes: resident and Bigg’s killer whales. The female relatedness with age is predicted to increase in both ecotypes, but with a less steep increase in Bigg’s due to their different social structure. Here, we show that there is a significant post-reproductive lifespan in both ecotypes with >30% of adult female years being lived as post-reproductive, supporting the general prediction that an increase in local relatedness with age predisposes the evolution of a post-reproductive lifespan. Differences in the magnitude of kinship dynamics however, did not influence the timing or duration of the post-reproductive lifespan with females in both ecotypes terminating reproduction before their mid-40s followed by an expected post-reproductive period of ~20 years. Our results highlight the important role of kinship dynamics in the evolution of a long post-reproductive lifespan in long-lived mammals, while further implying that the timing of menopause may be a robust trait that is persistent despite substantial variation in demographic patterns among population.

Peer review status:ACCEPTED

25 Feb 2021Submitted to Ecology and Evolution
26 Feb 2021Submission Checks Completed
26 Feb 2021Assigned to Editor
01 Mar 2021Reviewer(s) Assigned
03 Apr 2021Review(s) Completed, Editorial Evaluation Pending
12 Apr 2021Editorial Decision: Revise Minor
14 May 20211st Revision Received
15 May 2021Submission Checks Completed
15 May 2021Assigned to Editor
15 May 2021Review(s) Completed, Editorial Evaluation Pending
18 May 2021Editorial Decision: Accept