Gray Matters: The Minnesota Zoo's Dolphin Problem

Everyone loves the dolphins at the Minnesota Zoo. When one of them dies unexpectedly, especially a young pup, it raises uncomfortable questions about both the dolphins and those of us who love them.

Dolphin at Minnesota Zoo
Cameron Wittig
The trainers employ operant conditioning using positive reinforcement such as food and toys to work with the dolphins.

Lessard underlines Willis’s point that he’s the training staff’s John Wayne in her own words: “Kevin is the dolphin guy, for all dolphin questions.”

Even though I have Willis’s blessing to talk to the U of M veterinary staff, senior veterinarian Arno Wunschmann declines to speak with me, citing “the controversial nature of dolphins in captivity.” At Willis’s behest, Wunschmann releases the six necropsy reports on file since 2006 and agrees to answer e-mailed follow-up questions about the reports. This is the short version: One of the dolphins was a stillborn calf (2009), another was a dolphin with a congenital spine defect that lived 10 years longer than was predicted by the zoo’s medical staff before being euthanized (2006), two others died of what can be considered old age or at least natural causes (in both cases “respiratory failure,” one in 2006 and one in 2011). There’s nothing technical, no smoking gun such as an aquarium defect or bad fish, to blame for this run of bad luck. But two of the deaths are more troubling than the rest.

The first one, one of the three fatalities that took place in 2006, was Harley, a 7-month-old dolphin that ran into a wall between the pools. “It was a freak accident,” Willis says. “We were teaching him how to swim between the pools, and my analogy is you’ve taught your toddler how to go up and down the stairs, and he decides to do it by himself instead of waiting for mom and he falls. That’s what we think happened to Harley. We know there were trainers there and they heard a thump and they looked over and Harley had just hit the wall. And he was going fast enough to crack his skull.”

The necropsy has a different account. “The animal [Harley] was seen swimming in the pool without any evidence of disease during a training session on January 21, 2006,” it begins on U of M letterhead. “Few minutes later the dolphin was found on the deck and pushed back in the water since it appeared to be otherwise healthy. Few minutes later, blood was seen coming from the blowhole (under water) and attempts to nurse the animal by the mother were unsuccessful. A few minutes later, the animal was dead on the bottom of the pool at around 2:30 pm.” Toward the end of the report Wunschmann offers his conclusion: “The lesions of the head, skull, and brain are consistent with a massive trauma to the head causing fracture and meningeal and cerebral hemorrhage. The exact nature of the trauma is difficult to determine. The presence of soft tissue hemorrhage on both sides of the skull may indicate trauma from both sides at the same time or two (or more) subsequent traumatic events. The fractures occurred on the right side of the skull. This indicates that the most significant force was from the right side.”

Dolphins have an amazing anatomical ability to see their world acoustically. This superhero-esque sense is called echo-location, the ability to pitch a sound at an object or surface and receive a reading of where it is and what it looks like. Sort of like dolphin sonar. (Scientists have observed dolphins using their echolocation to see underneath the surface of the ocean while fishing for prey hiding under the sand.) This skill makes it seem unlikely that a dolphin would make the mistake of running into a wall or jumping clear out of a pool, but it does happen, according to Lori Marino, a dolphin and whale neurologist working out of Emory University in Atlanta.

Dolphins have an amazing anatomical ability to see their world acoustically. This superhero-esque sense is called echolocation, the ability to pitch a sound at an object or surface and receive a reading of where it is and what it looks like.

“It’s possible that [Harley] was running from another animal,” she says. The multiple trauma suffered from both the left and the right side of his cranium seems to indicate that Harley didn’t hit the wall head-on; rather, he either jumped or was thrown out of the pool, and either his head bounced when he came down on the deck or he was smashed into the wall by one of the five other dolphins living in the pool at the time.

Willis acknowledges that these are powerful animals, and at times they act aggressively toward one another. For example, he says, one of their dolphins used its fluke to flip a pup up onto the deck of the pool while the pup was swimming alongside its mother.

When Harley was alive, two dominant males lived in the pool, Semo and another middle-aged male, Chinook, who has since been moved to the Brookfield Zoo in Chicago.

The other puzzling fatality is the one that happened in February: Taijah’s. “We suspected she had a stomach ulcer,” Willis says. “We were treating her for an ulcer, and she was found to have an ulcer on necropsy.” Treating dolphins for stomach ulcers with an antacid injected in their fish is a common treatment at zoos and aquariums, he says. “Their stomachs are fairly acid because they have to digest fish bones. So it’s not uncommon to put them on medication. You put them on antacid and you don’t give them the largest fish, herring. You feed them capelin and mackerel. Ballpark for a dolphin is 20 to 25 pounds a day.”

I ask how it was determined that Taijah was suffering from an ulcer. “The number one clue is they stop eating. Taijah had been eating fine, and then about Thursday she decreased her consumption. That’s when we got a bit concerned. The vets came up, got a blood sample. Things looked all right. We decided to put her on stomach antacid, and she ate some, just not the normal amount. We had people staying overnight. Whenever a dolphin starts dropping consumption, we start monitoring breath rate. We had no idea that it was going south this quickly.” Willis says his staff informed him that Taijah skipped what would be her last meal on Sunday night, so they decided to “get their hands on her” on Monday morning. “We got our hands on her, got a blood sample. Everything seemed fine,” he says. “We gave her medication to help her appetite and her stomach issues, because we were suspecting ulcer.” He shakes his head. “We put her back in the pool, and she passed away later that night.”