An investigation into the oral health of captive orca whales has raised serious concerns about their teeth. Out of boredom and frustration, many of them turn to chewing on concrete and steel tank surfaces, causing wear and tear that leads to further problems. The research was published in Archives of Oral Biology and documented two types of teeth damage.
An international team of researchers has completed the first detailed investigation of the oral health of captive orcas, finding damage in all of the whales studied. It’s the first time that a quantitative study has evaluated the health status of individual teeth—not just for marine parks, but for the zoological community in general. Disturbingly, much of the damage observed was self-inflicted—but a likely consequence of orca confinement.
“First, whales will ‘chew’ on concrete and steel features of their tanks,” said Dr. Jeffrey Ventre, a former SeaWorld trainer and co-author of the new study. “This is a neurotic behavioral ‘stereotypy’ done out of boredom and perhaps to relieve anxiety.” Ventre says this behavior is similar to horses “cribbing” when they chew on the stalls in their barn, or tigers pacing back and forth in their small cages at zoos. As noted in the new study, more than 65 percent of the whales studied exhibited moderate to extreme tooth wear in their lower jaws, mostly as a result of this chewing behavior.
“Secondly, the other mechanism causes tooth fractures or breakage,” he said. “This is a very acute event, happening in literally seconds (not over the lifetime of the animal). This happens when captive killer whales do ‘threat displays’ at each other, usually when vying for dominance. The whales will snap their jaws at each other, usually when a steel gate is between them.”
The orcas often bite down on the steel bars of the gates, says Ventre, and this causes a painful fracturing of the tooth or teeth. “I have personally found teeth fragments on the bottom of Shamu Stadium in Orlando,” he said.
Carolina Loch from Otago University's Faculty of Dentistry, who co-authored the study, said more than 60 percent of the orca had "been to the dentist", which led to more problems. "Once the tooth gets worn to the point where the pulp is exposed this opens up a channel for disease and infection, so the staff then drill the teeth," she said. The resulting hole was not filled or capped, but left open, requiring daily flushing with chemicals in an attempt to manage infection. Drilled teeth were also severely weakened and easily broken, Dr Loch said. "We have documented more than 60 percent of the second and third teeth of the lower jaws were broken and this high number is likely linked to the drilling."
Co-author Professor John Jett of Florida's Stetson University, an ex-orca trainer, said the team found tooth damage started at a very early age in captivity. "Teeth are incredibly important to the overall health of an animal, and the results of our study should raise serious concerns for the health and welfare of captive orca," he said.
.Another researcher, New Zealand-based scientist Ingrid Visser, who has studied orca in the wild for more than three decades, said damage of this type or level was never seen among free-ranging orca. "We know that confining them in tanks is bad for the animals and this research now gives us some hard numbers to illustrate just how their health and welfare is compromised," said Dr Visser, a long-time campaigner against keeping orca in captivity. "Given how big the root of an orca's tooth is and that orca have a nervous system similar to ours, these injuries must be extremely painful."