Some marine mammals live longer in captivity, study finds

New research shows some marine mammals in captivity are living longer than before — and longer than their wild counterparts.

Hula is 17 years old. For harbour seals, that's considered middle age. 

She is a resident of the Edmonton Valley Zoo. Hula was found as a very young orphan pup off the coast of B.C., and nursed back to health in the Marine Mammal Rescue Centre. She was deemed non-releasable because she has seizures, the cause of which is unknown. 

Due to the advances in animal husbandry, plentiful high-quality food  — Hula's favourite is herring — and readily available veterinary care, she can expect to live longer than her wild cousins. 

A new study published in the Proceedings of the Royal Society B, found that the life expectancy of four marine marine mammal species commonly kept in zoological institutions around the world — harbour seals, California sea lions, bottlenose dolphins, and polar bears — is between 1.65 and 3.55 times longer in captivity than that of their wild counterparts.

The study also found that the lifespan of these four species in zoos and aquariums rose by 3.40 times between 1829 and 2020, as  animal welfare practices improved. 

"It's a clear indication that the improvements in care in captivity have really increased the survival of these animals over long periods of time," said Andrew Derocher, a professor at the University of Alberta who focuses on ecology, conservation, and management of large Arctic mammals, including polar bears, and one of the study's authors.

In captivity, Derocher said, the animals' nutritional needs are well-met, and medical problems can be treated. Wild animals, on the other hand, are on their own. There also are no predators trying to eat the animals in a zoo. 

The results of the study, Derocher said, reflect "the work that's been done by zookeepers, and handlers, and veterinarians to increase the quality of care of these animals in captivity," he added. 

Hula usually gets three training sessions every day. These sessions are mostly designed to train her for medical behaviours. The goal is to desensitize the animals to get them to participate in behaviours they may find stressful using positive associations. 

For example, Hula can put her nose into a device called anesthetic cone and breathe in and out on cue. 

"This is really important, because for marine mammals, if we need to do any type of anesthetic, they're able to voluntarily participate in that procedure, reducing stress," said Laura Castor, the animal care leader at Edmonton Valley Zoo.  

"The underlying golden rule of positive reinforcement training is it gives the animal choice and control to participate. So, if she wasn't interested, she would take off, and we would come back later when she was," Castor said. 

During every training session, keepers examine the animal to ensure there are no scrapes, cuts, bumps or bruises. It also desensitizes the animal to human touch, which is useful for procedures like blood draws.