Veterinarians said Wednesday that a killer whale that baffled biologists after swimming up a river in Alaska and remaining in the fresh water for weeks until her death had been pregnant.
A necropsy revealed that the orca was carrying a late-term fetus, veterinarians said. That could indicate that she was having pregnancy complications and "that may have been a factor in the whale dying," said Julie Speegle, spokeswoman for NOAA Fisheries Alaska Region.
The female orca was part of a trio of killer whales consisting of two adult females and a juvenile that was spotted for about three weeks in the Nushagak River. The necropsy was done by veterinarians on a beach in Dillingham, where the carcass was taken after she was found floating Saturday in the river in southwestern Alaska, a remote and mostly unpopulated part of the state.
Federal biologists have said the rare sighting represented an unprecedented journey into fresh water for the killer whales in Alaska.
The necropsy showed no evidence that the whale died because of human interaction, such as a boat strike or entanglement in fishing gear, said Judy St. Leger, director of pathology and research at SeaWorld who is a member of the necropsy team.
The veterinarians took samples from the whale carcass for tests and hope to answer some basic questions about its age, health, and pod identity. A full report was expected to take a month or two to complete.
"Other than the slimy film that was on the skin surface, there was no other overt evidence of infection," Speegle said.
The team also did not know yet why the whales were in the river. At one point, the distinctive black and white whales had ventured 30 miles upriver but were turned around and swam lethargically downriver toward Dillingham and the salt waters of Bristol Bay.
The second adult female was found dead Saturday, and the juvenile had not been seen since Saturday, Speegle said. She said it was possible the young whale also died in the river or made its way to the bay.
"The necropsy team is hoping that the picture will be a little bit clearer after they perform the necropsy on the second animal" later Wednesday, she said.