Slam dunk for otter health!

Sea Otter HoopsTraining animals in zoos is not just about enrichment – although that is certainly a worthy aim. Increasingly, trainers are working with veterinarians to condition animals for medical examinations and even therapy.

The benefits are obvious – being able to undergo diagnostic tests and treatments without the need for sedation and general anaesthesia minimises the potential for iatrogenic harm and builds a bond between the patient and veterinary team. But staff at Oregon Zoo in the United States discovered another benefit when their efforts to assist an aging otter went viral in a public relations coup.

The patient, a 15 year old male neutered southern sea otter (Enhydra lutris nereis), was admitted for a routine veterinary examination last year. Eddie has lived at the zoo since he was abandoned off the California coast as a pup. According to zoo experts, he would not have survived otherwise.

Life in the wild is tough for many otters. Southern sea otters are fully protected mammals under several state laws, having been designated as a threatened species in 1977. Once hunted for their pelts, an unknown number are now inadvertently killed through entanglement in fishing nets. Others become caught in crab and lobster cages. Gunshot wounds account for a small percentage of human-related mortality.

According to the published literature, sea otters are especially vulnerable to oil contamination, with oil spills from ships travelling along the California coast the primary threat to this species. Studies of stranded sea otters have revealed residues of chemicals including dichlorodiphenyltrichloro-ethane (DDT) and polychlorinated biphenyls (PCBs). There is a documented association between elevated concentrations of some chemicals, such as PCBs, and evidence of infectious disease, suggesting that chemical contaminants are a major driver of mortality. Lack of food and safe habitat likely also play a role.

Common afflictions of wild sea otters – as determined by necropsy studies of beach-cast carcases – include protozoal encephalitis (especially related to Toxoplasma gondii), shark attack and cardiac disease. Interestingly, otters killed by sharks or heart disease were more likely to have Toxoplasma-related encephalitis.

Eddie the Otter boasted a medical history that was largely unremarkable, with the exception of several tooth extractions secondary to tooth fractures, and chronic left corneal oedema. At fifteen, Eddie is considered geriatric – the average lifespan of a captive sea otter is 15 to 20 years.

According to veterinarian Mitch Finnegan, Eddie had been on contraceptives (delorelin) that suppressed his testosterone since March 2007, until he was surgically castrated in May 2012.

As patients, otters can be challenging.

“It depends on the otter,” Finnegan said. “Some otters, like Eddie, can be aggressive and bit when provoked. They have amazingly strong bites.

On the other hand, otters are highly trainable critters.

“Generally all of our interactions with the otters are facilitated through the trainers. We try to avoid anaesthetising these animals any more than we need to do when we do have them anaesthetised we usually give them full exams including bloodwork, urinalysis, radiographs and sometimes ultrasound – depending on how anaesthesia is going.”

Anaesthesia also provides an opportunity to administer routine treatments.

“In some areas they require heartworm prevention,” Finnegan said. “We do not do it here due to low risk. Internal parasites are typically not a big concern in captive environments. Our otters are not on regular vaccines, but some otters [at other institutions] are vaccinated for rabies, feline panleucopaenia and/or canine distemper, depending on the perceived risk.”

Eddie’s last full examination was performed when he was anaesthetised for castration. At the time Finnegan used a combination of fentanyl and midazolam.

“Nothing remarkable was found at the time except for very subtle signs of degenerative joint disease,” Finnegan said.

Mild degenerative changes were present in Eddie’s stifles, elbows and hips, despite a lack of clinical signs of arthritis.

Repeat radiographs were taken months later – this time using operant conditioning – to monitor progression of the disease. Keepers did not report overt signs of arthritis at the time.

“Many of our animals do not show overt signs of disease, including osteoarthritis, until it is very severe,” Finnegan said. “Treating an asymptomatic animal may seem like a stretch but we thought that if we could appreciate changes on radiographs that he was probably having some degree of pain from the joints, whether he showed it to us or not.”

Eddie was started on a conservative dose of meloxicam and misoprostol.

“We talked to the keepers in general terms about keeping him active and challenged without making it too hard core – that is, back off if he seems sore after working him.”

“They took the ball and ran with it,” Finnegan said.

In fact, keepers used a variety of activities – many ball related – to keep Eddie engaged and active.

Lead sea otter keeper Jenny DeGroot had to develop activities that exercised all of Eddie’s joints – including his elbows. There aren’t many natural opportunities for sea otters to work their elbow joints as they don’t use their front limbs to swim. According to DeGroot, they swim by moving their hindlegs and flipper.

But sea otters are incredibly dextrous critters. They use rocks to open clam shells. DeGroot had to develop activities that could employ this dexterity to provide some physiotherapy for Eddie’s elbows.

He had already been trained to retrieve an object and bring it to the keeper’s hand on cue – an activity he enjoyed. At some point, trainers developed the idea that being able to pick up and throw the ball would help Eddie move his elbows in just the right way.

Keepers began by raising their hands in higher increments to encourage Eddie to reach up out of the water.

“Once he had that motion down, they added in a hoop,” DeGroot said. “As keepers held a under under the hoop, Eddie learned to bring the ball up over the hoop to deliver it to the keeper’s hand. Eventually, we took away the hand, and let Eddie drop the ball through the hoop, pairing this behaviour with a verbal cue.”

Essentially, the basketball behaviour was trained by asking Eddie to retrieve the ball and bring it to the keeper – just incorporating the hoop into the process. Incredibly, it took just a week for Eddie to learn the new trick.

Of course there had to be a reward – aside from verbal praise, something otters respond very positively to, there were delectable seafood items like prawns, clams, fish and squid on offer.

The behaviour is not performed for the public but occurs behind the scene’s during Eddie’s private physiotherapy sessions. DeGroot says that Eddie has excellent aim, barely missing – but trying again when he does.

According to Finnegan, the credit for Eddie’s improvement goes to the trainers.

“They are amazing trainers and very dedicated to doing what is best for all of their animals,” Finnegan said. “They are thoughtful and proactive and jump in to projects like this with great enthusiasm. If it was not for their efforts our ability to provide medical care for their animals would be extremely limited.”

Eddie remains comfortable and continues to shoot hoops. He will turn 16 later this year.

A video of Eddie performing his basketball exercises, together with an interview of trainer Jenny DeGroot, can be viewed online at


Anne Fawcett

Picture: Oregon Zoo


Estes JA et al. (2003) Causes of mortality in California sea otters during periods of population growth and decline. Marine Mammal Science 19(1):198-216.

Kreuder C et al. (2003) Patterns of mortality in southern sea otters (Enhydra lutris nereis) from 1998-2001. Journal of Wildlife Diseases 39(3):495-509.

Kreuder C et al. (2005) Evaluation of cardiac lesions and risk factors associated with myocarditis and dilated cardiomyopathy in southern sea otters (Enhydra lutris nereis). American Journal of Veterinary Research 66:289-299.

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