[MARMAM] Latest killer whale life history paper

Naomi Rose naomi at awionline.org
Fri Jul 17 08:21:37 PDT 2015


The Journal of Mammalogy has published an early-view paper by Robeck et al. entitled "Comparisons of life-history parameters between free-ranging and captive killer whale (Orcinus orca) populations for application toward species management" (http://jmammal.oxfordjournals.org/content/early/2015/07/09/jmammal.gyv113). Based on the paper's analyses, the authors suggest that it is likely that "the estimated ages assigned to [northern and southern resident killer whales] at the start of the study period (1973 - Bigg et al. 1987; Olesiuk et al. 1990) were inaccurate." They go on to say "Our analysis supports a proposed longevity of between 60 and 70 years for females and 50 and 60 years for males, with the vast majority (>97%) of animals dying by age 50. This is substantially less than the longevity of 80-90 years for females and 60-70 years for males that have [sic] been previously suggested."

The authors also state that "Reproductive senescence in killer whales, often erroneously termed menopause, has been proposed as a relatively unique strategy for the transmission of information related to population fitness (Foster et al. 2012; Brent et al. 2015; Whitehead 2015) or reproductive success (Ward et al. 2009b). However, reproductive and actuarial senescence is common in mammalian species studied to date (for review, see Nussey et al. 2013) and it therefore should not be considered an unexpected finding in killer whales."

Finally, they note "While life tables would provide a more accurate age-specific estimation of longevity, they are inappropriate for the 3 populations analyzed in this study [that is, southern and northern resident killer whales and SeaWorld killer whales] since no known-age animals have died in the older age groups...Thus, for the time being, [mean life expectancy] and [average life expectancy] based on overall population [annual survivorship rate] may be the most accurate measure [sic] of longevity."

Given that this paper concludes that concepts long-accepted in the marine mammal science community for killer whales are or are likely incorrect, those who have examined killer whale life history traits and social structure in the past might wish to know of and read/review this paper.



Marine Mammal Scientist

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