A long post-reproductive lifespan is a shared trait among genetically distinct killer whale populations

• Published in: Ecology and Evolution
• Main Authors: Nielsen, MLK, Ellis, S, Towers, JR, Doniol-Valcroze, T, Franks, DW, Cant, MA, Weiss, MN, Johnstone, RA, Balcomb, KC, III, Ellifrit, DK, Croft, DP
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley / European Society for Evolutionary Biology / Society for the Study of Evolution 2021
• Subjects: Kinship dynamics; post-reproductive lifespan; menopause; Orcinus orca; Killer Whale; Orca; toothed whales; Killer whale
• Online Access: http://hdl.handle.net/10871/125756; https://doi.org/10.1002/ece3.7756

This is the final version. Available on open access from Wiley via the DOI in this record Data availability: Data to replicate the analyses are available from the online repository: https://doi.org/10.5061/dryad.6t1g1jwxx. Requests for access to raw data can be directed to the authors, the Center for Whale Research (www.whaleresearch.com) or Fisheries and Oceans Canada (www.dfo-mpo.gc.ca) 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 populations. Nuffield Foundation Natural Environment Research ...