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MAMALOGY
Lifespan of animals kept in parks is at centre of dispute.
In a decision hailed by animal-rights groups, the US marine-park company SeaWorld Entertainment announced last week that it will no longer breed killer whales. But whether captivity harms the planet's biggest predator is an area of active scientific debate.
The latest arguments centre on two 2015 studies that drew dramatically different conclusions about the lifespans of captive killer whales (Orcinus orca), relative to those of wild populations. Although many factors affect wellbeing, an apparent discrepancy between the survival of captive and wild animals has long been cited by activists as evidence of the poor welfare of captive killer whales.
One of the studies1 is authored by a team largely made up of researchers at SeaWorld, which is headquartered in Orlando, Florida, and owns several animal parks that keep killer whales; the other2 is by two former killer-whale trainers at the company who feature in the 2013 documentary film Blackfish, which is critical of SeaWorld. In letters published last week3,4, authors from each paper accuse the others of cherry-picking data to support positions on whether the animals should be captive - charges that each team in turn rejects.
Although SeaWorld's captive-killer-whale programme now has an expiration date, the company's existing 23 animals will remain in parks for the rest of their lives, and its pregnant female Takara will give birth in captivity. Another 33 animals are held in other marine parks around the world.
Robust studies of killer whales' longevity are needed to improve the well-being of the remaining captive animals, says Douglas DeMaster, science director at the US...