Oregon Sea Lions Likely Died of Heat Stroke
Posted on: Thursday, 15 May 2008, 15:00 CDT
Heat stroke probably killed six sea lions enclosed within a pair of floating cages near Bonneville Dam a week and a half ago, according to federal authorities.
The disclosure Wednesday lends new insight -- while raising new questions -- over the puzzling deaths of four California sea lions and two threatened Steller sea lions sometime between 7 p.m. on May 3 and the time they were discovered in the floating docks at 11:30 a.m. May 4.
The National Marine Fisheries Service reported Wednesday that necropsies on all six animals are consistent with death from heat prostration -- even though air temperatures at the time were mild. Vancouver's high for May 4 was 73 degrees, and it only reached 59 degrees on May 3.
And sea lions typically haul out of the water for much longer periods of time than the animals that died at Bonneville.
"It's something that we don't normally see," said Steve Jeffries, marine mammal specialist for the Washington Department of Fish and Wildlife in Tacoma. "These animals rest in the hot sun for hours."
However, he said the animals may have become stressed while trapped in the cages.
"They're like a big insulative blanket," Jeffries said, referring to the animals' blubber. "If they can't dissipate their heat because they're in a trap, it's just like a person in heat distress. If you can't cool down, you're going to go the wrong way."
The agency reported that more conclusive results may be available once studies of tissue samples taken from the dead animals are completed in about 10 days. Meanwhile, the investigation by the Washington and Oregon departments of fish and wildlife, the National Marine Fisheries Service and the Army Corps of Engineers continues.
The animals died in floating docks set up by state authorities to trap and relocate sea lions that had been eating a growing number of Endangered Species Act-protected salmon below Bonneville Dam. A pair of trap doors had been triggered sometime late that Saturday night or early Sunday, raising the possibility that someone manually closed the doors as the animals lounged on a side-by-side pair of floating docks. (The doors normally remained open, allowing the sea lions to freely come and go until state authorities triggered the doors to capture the pinnipeds.)
Last week, authorities backed off initial reports that the animals had been shot.
Officials were also considering the possibility that the doors closed on their own due to fluctuating river levels below the dam, although fisheries service spokesman Brian Gorman said Wednesday that such a scenario appeared "unlikely." River levels fluctuated by just under 3 feet overnight May 3-4, which Gorman said is well within the range of normal in the tailrace below the dam.
"How did the trap doors close, and both at the same time?" said Sandra Jonker, regional wildlife biologist for the state Department of Fish and Wildlife in Vancouver. "There are just so many questions that we're trying to find the answers to."
Gorman said investigative documents will be released when the investigation is completed.
The Humane Society of the United States, which previously sued to block a federal lethal-removal permit on salmon-eating sea lions, is intent on reviewing those documents.
"We certainly look forward to actually being able to see a full report and hope that we can have some independent verification," said Sharon Young, marine issues director for the organization. "In any case, the deaths are the result of human action: Either people killed them, or, through its negligence, the government is responsible for their deaths. They deliberately attract them to these cages, and they have a responsibility to ensure their welfare."
Source: The Columbian
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