Anore, the 10-year-old female beluga whale that died yesterday at the National Aquarium in Baltimore, probably was killed by a dolphin that suddenly and mysteriously became aggressive during a routine training session, officials said today.
Doug Messinger, curator of marine mammals at the aquarium, said a necropsy, or animal autopsy, showed that the whale "sustained a blow to the left chest."
"Several ribs were broken and that blow caused her heart to rupture," he said.
Messinger said several trainers were present yesterday during the session. "No one witnessed what happened but the strongest theory is that a dolphin delivered the blow to the whale's chest," he said.
Messinger said the whales and dolphins were in a pool as part of a three-month-long period of "social interaction."
"They were starting to get comfortable with each other," he said. " . . . they had chased each other before during these sessions."
But yesterday, he said, the aquarium's three beluga whales were chasing two dolphins when the dolphins "turned and began chasing the whales."
"At that point, we decided to remove the dolphins from the pool," he said. "Everything appeared to be normal until about 25 min
utes later we saw Anore listless, at the top of the pool. She was dead."
Messinger said dolphins will sometimes use their rostrums, or noses, as a weapon when threatened or angry. They also can use their tails to strike, he said.
Powerful swimmers, dolphins can generate tremendous velocity in a very short distance before striking their targets.
"This is absolutely what killed her," Messinger said. "Again, no one saw it but there is no other explanation."
Anore died about 1 p.m. after performing in a show and the training session with the dolphins, according to Vicki Aversa, public relations manager for the aquarium.
"It's like losing a family member," Aversa said. "We are saddened by this unexpected loss."
The death could be expected to trigger protests from animal rights activists who have staged demonstrations at the aquarium, protesting the showing of whales and dolphins in performances. They also say it is cruel to keep the animals in captivity. The protesters have targeted a number of aquariums nationwide.
Anore and Illamar, another female beluga whale, arrived at the aquarium in 1985 after they were caught in the Churchill River in Manitoba, Canada. Illamar died in 1989 of a bacterial infection.
The whales and dolphins are confined to the $35 million Marine Mammal Pavilion, which opened last year. The pavilion generated some controversy when Florida threatened the aquarium with criminal charges for trying to capture dolphins there.
Anore had become acclimated to both the main aquarium and the pavilion, Aversa said, and was in good health.
The remaining female beluga whales, Kia and Sikku, and the aquarium's dolphins are in good health and don't yet seem to be affected by Anore's death, Aversa said. But they are being monitored.
Two dolphins, Hailey and Shiloh, are pregnant. They were captured in the Gulf of Mexico in 1981, acquired from a Florida company and flown to Baltimore in October 1990. They became pregnant in late February or early March.
Hailey, 12, began to show complications a few months ago.
The aquarium hopes to develop a breeding program for its marine mammals. The dolphins' gestation period is 12 months. With three months still to go in the pregnancy, the aquarium staff is preparing for a crisis.
Aversa said the aquarium will be open tomorrow during normal holiday hours, 10 a.m. to 1 p.m. Two shows featuring the mammals are scheduled.