UF veterinarians: behavior change is related to hearing loss in stranded animals
Several years ago, University of Florida aquatic animal veterinarian Michael Walsh, D.V.M., noticed a concerning pattern among some stranded dolphins after they had been rescued. Both of the dolphins returned to the beach again once they had been released back into the wild.
“I worked with two animals, one directly, that showed numerous behavioral problems while in rehab,” said Walsh, a clinical associate professor of aquatic animal health at the UF College of Veterinary Medicine.
“We weren’t able to test the first dolphin’s hearing, but the second animal was tested at Mote Marine Laboratory and found to be totally deaf. This suggested that the problem of adapting to new environments might be hearing-related and might be more common than we had initially thought,” he said.
When Megan Strobel, D.V.M., then a first-year veterinary medical student at UF, went to Walsh, her faculty mentor, in 2013 to discuss a possible research project, he suggested that she might compare hearing capacity and behavior changes in wild and facility-housed dolphins. The result of their collaboration, which also involved numerous other individuals and organizations, was a study that appeared in December in the Journal of Zoo and Wildlife Medicine.
The study found that stranded animals with hearing deficits showed markedly different behaviors than their counterparts with normal hearing and concluded that hearing assessments should be routinely administered as part of regular health examinations in all animals under human care.
Hearing is the primary sense of odontocete cetaceans, also known as toothed whales, which include dolphins, porpoises and all other whales possessing teeth. Currently, little empirical information on the relationship between odontocetes and hearing loss reaches those taking care of the animals, the researchers said.
Hearing loss in odontocetes can be caused by loud noises, parasites, trauma and medical issues such as infection, just as it can in humans. But the loss of sonar capability, which relies on hearing, is especially difficult and traumatic for the wild individual, Strobel said.
“How often when you go to the doctor do you have your hearing tested? You have to do that separately,” Walsh said. “If we recognize that all animals will lose hearing over time, then putting technology such as the auditory evoked potential test we used into their health exams as they get older will help everyone understand how their sensory systems are doing.”
For animals that have grown up in facilities, the environment is known and their daily lives are somewhat predictable, Walsh said.
"But if you change the environment on a deaf animal, it’s similar to changing the environment on a human individual,” he said. “They have to give more effort to understanding the new environment and what it means.”
The researchers felt it was important to educate caretakers about challenges the animals face in situations where hearing deficits in older animals or deafness may result in behavior that is misunderstood. This knowledge should create a level of empathy with the animals, improving their welfare with the human interaction needed, they said.
Just like people, all animals as they age can potentially lose some of their senses, like hearing and sight. The long-term health and wellness assessments of those creatures should include the same considerations as would be applied to an older human being, the researchers said.
“And for their cohorts in the wild, we need to understand the implications of hearing loss so we can approach those animals differently at a time they are trying to adapt to a rehabilitative environment with the loss of their most important sense,” Walsh said.
Walsh said Strobel’s ability to focus on this particular project as part of her curriculum requirements meant she was able to efficiently complete necessary tasks, no matter what the challenge.
“It was her dedication that made the project work with so many partners, including SeaWorld’s veterinary and training teams, The National Marine Mammal Foundation, the International Fund for Animal Welfare, Dolphins Plus, Dolphin Research Center, Gulf World and Clearwater Marine Aquarium,” Walsh said of Strobel, who graduated from the UF veterinary medical college in 2017 and is now working as an intern at Friendship Hospital for Animals in Washington, D.C. She will move to Vancouver in July to begin a veterinary fellowship at the Vancouver Aquarium.
“Dr. Strobel made a big difference in spreading the knowledge of our understanding of what these animals may need in many situations,” Walsh said.
The University of Florida College of Veterinary Medicine is supported through funding from UF Health and the UF Institute of Food and Agricultural Sciences.