Abstract
Data available1-6 on survivorship parameters of known-age animals from the northern and southern resident killer whales (Orcinus orca) of the eastern North Pacific (SR: southern residents, 1975 to 2014; NR: northern residents, 1975 to 2013) were compared with estimated (based on length at capture) and known-age killer whales located at SeaWorld Parks and Entertainment (SEA: 1965 to 2015). The overall mortality rate (MR) for SEA of 4.8% was not significantly different than the 2.3% MR observed for NSR (p = 0.87). SEA MR decreased each ten-year block from 1972 through 2013 at 7.8, 5.0, 3.5 and 2.6%, respectively. Annual survival rate (ASR) for SEA increased over approximate 15-year increments with rates in the most recent block (2000 to 2015 ASR: 0.977) improved (p = 0.001) over the initial period of captivity (1965 to 1985: 0.911). Both the NR (0.979) and SR ASR (0.967) were higher (p = 0.01) than that of SEA until 2000, after which neither population was improved over SEA. However, the NR ASR was higher (p = 0.002) than the SR ASR. No differences (p > 0.05) were detected in survivorship patterns between SEA, and NR or SR in 10-year age groups (0 to 9, 10 to 19, 20 to 29, 30 to 39, ≥ 40). While differences (p = 0.002) were detected in male (but not female) survivorship patterns between NR (male: 0.976, female: 0.982) and SR (male: 0.956, female: 0.976), none were detected when each wild population was compared to animals of either sex born at SEA (male: 0.982, female: 0.975). Based on population ASR, median and average life expectancy were 29.1 and 41.1 years (SEA: 2000 to 2015), 20.3 and 29.4 (SR), and 32.5 and 46.8 years (NR), respectively. These data present evidence for very similar survivorship parameters of in situ and ex situ killer whale populations, and provide support for the premise that ex situ killer whales can be used for understanding those in the wild. The baseline information established herein on survivorship patterns has application for use in future research concerning the overall health of both populations.
Acknowledgements
We acknowledge the efforts of R. Baird, K. Balcomb, M. Bigg, G. Ellis and J. Ford, for collecting and disseminating data on wild killer whale populations; without their initial and continued efforts, this comparative work could not have been possible. We thank the animal training, animal care and veterinary staff of SeaWorld Parks and Entertainment and Mr. Brad Andrews for their support of this project.
* Presenting author
Literature Cited
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