Study
Life history and population dynamics of northern resident killer whales (Orcinus orca) in British Columbia
Olesiuk, Peter F.; Ellis, Graeme M.; Ford, John K. B.
Fisheries and Oceans Canada, Canadian Science Advisory Secretariat Research Document 2005/045, 2005
Every individual in the northern resident population is identifiable from the shape of the dorsal fin and the pattern of the saddle patch, so the population has been censused photographically for decades. Births, deaths and maternal relationships are recorded rather than estimated, which is what makes life-history parameters calculable at all.
- Studied in
- Orcinus orca
- Sample size
- decades of photo-identification records of a known population
Females bear their first surviving calf at around 14 years, produce a calf roughly every five years, and stop reproducing in their late thirties to early forties while frequently living decades longer. Mean life expectancy for females that survive to adulthood is around 50 years with a maximum in the eighties; males average around 30 with a maximum near 60. Gestation is roughly 17 months and calves nurse for over a year.
What it means
The authors' reading, and ours. Where they differ, that difference is the point.
How the authors put it
The northern resident population shows a life history of late maturity, slow reproduction, marked sexual difference in longevity, and a long post-reproductive female lifespan.
How NatureHQ reads it
Photo-identification is what turns "how long do orcas live?" from a guess into a measurement, and it is why the answer has to be given with the population and the sex attached. The commonly quoted figures conflate males and females, and the captive figures are a different question again. The post-reproductive lifespan is the genuinely unusual finding: very few mammals do it, and in orcas the females that have stopped breeding lead the group.
- One population in one region; other ecotypes and populations differ.
- Photo-identification records births and deaths reliably and causes of death rarely.
- Maximum ages for the earliest-catalogued animals are estimates, since the study began mid-life for them.
What this study is used for on NatureHQ
One study can inform several subjects. Here is everywhere this one is cited.
Orca
Female orcas outlive males by decades, and the famous numbers describe one population
Orca
Each resident orca pod uses its own set of calls, passed down the maternal line and stable for decades.
Orca
Different orca populations hunt different prey in different learned ways, and the differences are not explained by what is available to eat.
Published by: Government science agenciesPublished by a national science or fisheries agency.
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