The unusually swollen tongue of a dead humpback whale may indicate that it perished after colliding with a ship in the waters of southeast Alaska, scientists say.
The humpback, an endangered species, also suffered heavy internal bleeding and bruising under its right pectoral fin, suggestive of blunt-force injury, said Aleria Jensen, a scientist at the National Oceanic and Atmospheric Administration in Alaska.
Scientists believe some sort of impact forced air into the tongue of the 40-foot male humpback, said Jensen, a marine mammal stranding coordinator for the agency. They had initially guessed that the swelling indicated a severe infection.
"It's certainly possible that it was a ship strike, but that's still inconclusive," Jensen said Monday.
According to a recent report prepared for the International Whaling Commission, the Alaska Marine Mammal Stranding Database contains records of about 60 collisions between large whales and ships in Alaska since the 1970s.
The humpback population roaming the North Pacific, estimated at about 10,000, is believed to have been growing at an annual rate of about 7 percent since the mid-1990s. But researchers have said that as the whale population increases, boat strikes become more likely.
A Juneau-based tour boat first reported seeing the whale on July 7 as it struggled to swim with a giant, inflated tongue. Two state ferries also reported the sighting.
"When we flew out to find it, it was on its side struggling to get its blowhole above water," said Jensen. "Its tongue was the size of a small car."
The whale was found dead Wednesday after tides washed it onto a steep, rocky beach on the shore of Admiralty Island south of Juneau. It had been seen and numbered by biologists in the past, and it had been sighted several times since 1992.
Scientists performed a necropsy Friday, and they plan to study samples of skin, blubber and stomach contents as well as the intestines, liver and kidney tissue, Jensen said. Once it decomposes, they will investigate whether it suffered broken bones. The analyses could take several weeks, Jensen said.
"There's never any guarantee that we can find the cause of death, but that's always our goal," she said.