title: Mortality rate acceleration and post-reproductive lifespan in matrilineal whale species.
abstract: The strength of selection to increase the span of a life stage is dependent upon individuals at that stage being able to contribute towards individual fitness and the probability of their surviving to that stage. Complete reproductive cessation and a long post-reproductive female lifespan as found in humans are also found in killer whale (Orcinus orca) and short-finned pilot whale (Globicephala macrorhynchus), but not in the long-finned pilot whale (Globicephala melaena). Each species forms kin-based, stable matrilineal groups and exhibits kin-directed behaviours that could increase inclusive fitness. Here, the initial mortality rate and mortality rate-doubling time of females of these three closely related whale species are compared. The initial mortality rate shows little variation among pilot whale species; however mortality rate accelerates almost twice as fast in the long-finned pilot whale as it does in killer whale and short-finned pilot whale. Selection for a long post-reproductive female lifespan in matrilineal whales may therefore be determined by the proportion of females surviving past the point of reproductive cessation.
authors.affiliation: Lighthouse Field Station, School of Biological Sciences, University of Aberdeen, George Street, Cromarty IV11 8YJ, UK. a.d.foote@abdn.ac.uk
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Foote
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D005260:Female; D008136:Longevity / Q000502:physiology*; D009026:Mortality; D012098:Reproduction / Q000502:physiology*; D012641:Selection, Genetic; D013045:Species Specificity; D014907:Whales / Q000502:physiology*