Analyses of ovarian activity reveal repeated evolution of post-reproductive lifespans in toothed whales

This is the author accepted manuscript. The final version is available from Springer Nature via the DOI in this recordIn most species the reproductive system ages at the same rate as somatic tissue and individuals continue reproducing until death. However, females of three species – humans, killer whales and short-finned pilot whales – have been shown to display a markedly increased rate of reproductive senescence relative to somatic ageing. In these species, a significant proportion of females live beyond their reproductive lifespan: they have a post-reproductive lifespan. Research into this puzzling life-history strategy is hindered by the difficulties of quantifying the rate of reproductive senescence in wild populations. Here we present a method for measuring the relative rate of reproductive 25 senescence in toothed whales using published physiological data. Of the sixteen species for which 26 data are available (which does not include killer whales), we find that three have a significant post27 reproductive lifespan: short-finned pilot whales, beluga whales and narwhals. Phylogenetic reconstruction suggests that female post-reproductive lifespans have evolved several times independently in toothed whales. Our study is the first evidence of a significant post-reproductive lifespan in beluga whales and narwhals which, when taken together with the evidence for post31 reproductive lifespan in killer whales, doubles the number of non-human mammals known to exhibit post-reproductive lifespans in the wild.Support for this research was provided by a grant from NERC (NE/K01286X/1) awarded to DPC, DWF and MAC