SEATTLE (AP) - Two years after a young endangered orca washed ashore bloodied and bruised in southwest Washington, investigators have concluded the whale was hit, struck or rammed in the head and neck. But they couldn't determine the source of that blow.
In a report released Tuesday, the team of veterinarians and biologists ruled out possible sources of the blunt-force trauma, including sonar and small underwater explosive activity reported by the Royal Canadian Navy in waters off Vancouver Island.
"This whale was killed from a blunt-force trauma, but (despite) every effort possible, we couldn't tell if it came from another ship or whale," said Joseph Gaydos, a co-author of the report and wildlife veterinarian with SeaDoc Society, a program of the Wildlife Health Center at the University of California, Davis' School of Veterinary Medicine. "The evidence doesn't support that it was a sonar episode or explosion."
The investigation found that the orca, known as L-112, likely died too far south of the Canadian naval exercises, and that no other military activities involving sonar or explosives took place in the area of the whale at the time of her death.
Some whale advocates had raised suspicions that the orca's injuries were linked to an underwater explosion or military training activity at sea.
The 3-year-old whale washed ashore in Long Beach on Feb. 11, 2012. She was a member of the "L'' pod, one of three groups of federally protected southern resident killer whales that frequent Puget Sound. The loss of a female capable of reproducing was devastating to the population, which now numbers 80.
The report by the Northwest Marine Mammal Stranding Network said the U.S. Navy, the U.S. Army and the U.S. Coast Guard reported no training or military activities on the coast during the time of the orca's death.
NOAA Fisheries' hydrophone recorders also did not detect sounds from mid-frequency sonar or explosions in early February.
The Royal Canadian Navy confirmed sonar and small underwater explosive activity in early February off Vancouver Island and in the Strait of Juan de Fuca, but the investigators said the activities occurred too far to the north to be considered.
Because of prevailing currents and eddies, it was unlikely that the orca died in Canadian waters or the Strait of Juan de Fuca and drifted south, but likely died in the mouth of the Columbia River or farther to the south along the coast of Oregon, investigators said.
Howard Garrett, executive director of the Orca Network, a nonprofit that raises awareness about whales, questioned the results.
"That to me is unsatisfactory, because it could lead to its happening again," he said, adding that he thinks the whale died from an explosion.
Results from extensive bacterial, viral, molecular and toxicological tests were inconclusive.
"We're satisfied that we did the best we could with the actual data that could be gleaned from whatever source," said Brent Norberg, NOAA's marine mammal coordinator for the West Coast region.
Even in the best of circumstances, determining the exact cause of death would be tough, Norberg said.
Without witnesses, investigators had to recreate what happened based on the condition of the body and what evidence they could find. They also had to paint a picture about the environment, Norberg said.
NOAA Fisheries oversees stranding networks across the nation. The report was written by multiple authors, including from Portland State University, Cascadia Research Collective, the state Department of Fish and Wildlife and NOAA Fisheries.