Current Biology
Volume 25, Issue 6, 16 March 2015, Pages 746-750
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Ecological Knowledge, Leadership, and the Evolution of Menopause in Killer Whales

https://doi.org/10.1016/j.cub.2015.01.037Get rights and content
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Highlights

  • Postreproductively aged female resident killer whales lead collective movement

  • Leadership by postreproductive females is most prominent when food abundance is low

  • Sons are more likely than daughters to follow their mothers

Summary

Classic life-history theory predicts that menopause should not occur because there should be no selection for survival after the cessation of reproduction [1]. Yet, human females routinely live 30 years after they have stopped reproducing [2]. Only two other species—killer whales (Orcinus orca) and short-finned pilot whales (Globicephala macrorhynchus) [3, 4]—have comparable postreproductive lifespans. In theory, menopause can evolve via inclusive fitness benefits [5, 6], but the mechanisms by which postreproductive females help their kin remain enigmatic. One hypothesis is that postreproductive females act as repositories of ecological knowledge and thereby buffer kin against environmental hardships [7, 8]. We provide the first test of this hypothesis using a unique long-term dataset on wild resident killer whales. We show three key results. First, postreproductively aged females lead groups during collective movement in salmon foraging grounds. Second, leadership by postreproductively aged females is especially prominent in difficult years when salmon abundance is low. This finding is critical because salmon abundance drives both mortality and reproductive success in resident killer whales [9, 10]. Third, females are more likely to lead their sons than they are to lead their daughters, supporting predictions of recent models [5] of the evolution of menopause based on kinship dynamics. Our results show that postreproductive females may boost the fitness of kin through the transfer of ecological knowledge. The value gained from the wisdom of elders can help explain why female resident killer whales and humans continue to live long after they have stopped reproducing.

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This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).