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Keywords:

  • captive killer whale;
  • Orcinus orca ;
  • Kaplan-Meier;
  • Cox proportional hazard;
  • annual survival rate

Abstract

Killer whales (Orcinus orca) were first placed into captivity in 1961 and are now found in theme parks around the world. Despite successful breeding of captive killer whales since 1985 there is growing concern for their welfare in captivity, which often includes claims of poor survival. We employed Kaplan-Meier and Cox Proportional hazards models and annual survival rate analyses on 201 captive killer whales to discern how sex, facility (U.S. vs. foreign), captive-born vs. wild-captured, pre- vs. post-1 January 1985, and animal age upon entering captivity affect survival. Overall median survival estimate was 6.1 yr, with no difference between male and female survival. Killer whales in U.S. facilities (12.0 yr) demonstrated a significantly higher median survival than those in foreign facilities (4.4 yr), as did whales entering captivity post-1 January 1985 (11.8 yr) vs. those entering prior to 1 January 1985 (3.9 yr). Median survival for captive-born (14.1 yr) was significantly higher than wild-captured killer whales (5.5 yr), though the two failed to differ among the post-1 January 1985 cohort. Facility location and pre- vs. post-1 January 1985 were predictors of the hazard rate. Survival of captive killer whale cohorts has generally improved through time, although survival to age milestones are poor when compared to wild killer whales.