Study Shows Captivity Curtails Orca Lifespan

In 1995, Robert Small and Douglas DeMaster calculated annual survivorship rates (ASRs) in captive orcas and compared these results to the ASRs of wild orcas living in the Pacific Northwest of North America. Their results, published in the journal Marine Mammal Science, indicated that orcas in captivity had a mortality rate (the inverse of survivorship) 2.5 times higher than orcas in the wild. This difference was highly statistically significant.

Small and DeMaster hypothesized that, as time passed and husbandry improved, and as more orcas were born in captivity (rather than caught in the wild), survivorship in captivity would one day equal or surpass that in the wild. For years, the captive display industry, most notably SeaWorld Entertainment, has implied that this hypothesis has been confirmed. Despite having no scientific data to back up the claim, industry public relations rhetoric routinely implies that captive orcas survive as well as—if not better than—wild orcas.

In a new paper published in Marine Mammal Science in May, John Jett and Jeffrey Ventre re-examined captive orca survivorship. Although they presented updated ASRs, they primarily worked with an analytical method from the medical field, the Kaplan-Meier model. This model evaluates the efficacy of pharmaceuticals such as heart or blood pressure medication by measuring survival of patients over specified periods of time after clinical intervention. Jett and Ventre recognized that captivity could be viewed as a sort of pharmaceutical affecting the survival of orcas, making the model a valid statistical approach for this situation.

Unsurprisingly, they found that captivity shortens rather than lengthens the lives of captive orcas. As Small and DeMaster hypothesized, survivorship rates of captive orcas have improved with time (and are higher when whales are born in captivity rather than removed from the wild). Survivorship is also better in the United States than in foreign facilities. However, the survival of captive orcas to certain age milestones is poor compared to that of orcas in the wild. For wild females, up to 81 percent reach sexual maturity (15 years) and up to 75 percent achieve menopause (40 years). In captivity, maximum values for these milestones are 46 percent and 7 percent, respectively.

Jett and Ventre also noted that certain life stages are particularly hazardous for captive orcas. “Survival deteriorates” during the age ranges when captive-born whales are typically transferred from one facility to another for husbandry purposes (at weaning and at sexual maturity). Consequently, they caution against “potentially stressful separation[s]” of mothers and offspring, a common feature of captive orca management.

Wildlife living a long life in captivity does not guarantee living conditions are humane—quality of life can suffer even if quantity of life does not. When, however, wildlife does not survive well in captivity—given that they are otherwise removed from whatever dangers that might cut their lives short in the wild—it is a sure sign of poor welfare. The Jett-Ventre study is yet another indication that orcas do not belong in captivity.

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