A Northern bottlenose whale that swam up the River Thames last week, splashing past Big Ben and the Houses of Parliament before dying during a rescue effort, suffered from a combination of dehydration, kidney failure and muscle damage, scientists said Wednesday.

The lost, 19-foot-long marine mammal swam up the river while using her "innate sense of direction" to try to find her way back to her natural North Atlantic habitat, scientists said.

There appeared to be no physical explanation for the whale's trip up the Thames, so experts believe she was using her instincts to try to find her way home, said Paul Jepson, a veterinary pathologist with the Zoological Society of London.

"Some scientists have speculated that Northern bottlenose whales ... get into the North Sea by taking a wrong turn at Scotland, and then use their innate sense of direction to go back west," he said. "We think this could be the most likely scenario for the Thames whale.

"While we do not know for sure that the whales are aware that they need to go west, it is one theory that has been proposed that makes sense and that would also explain that, despite the presence of humans in the river, she continued to try to swim west."

It also was "very unlikely" that military sonar had anything to do with the whale losing her way, Jepson said.

The whale first appeared in the Thames in central London on Friday, captivating onlookers crowded along the river's banks to watch her progress. The whale died Saturday evening during a rescue operation to transport her to the sea on a salvage barge.

She was dehydrated because she had been unable to feed on her usual diet of deep water squid, which hydrates the whales, Jepson said.

"This follows a period of up to three days in the Thames, an environment to which the animal is not suited," he said. "This animal would not have been able to feed while in the [relatively shallow] North Sea and so would have become dehydrated."

Scientists will continue to perform tests to determine if the whale had a bacterial or viral infection.

The whale was no older than 11, which is young, and no longer reliant on its mother for food. Jepson said she likely was a healthy, fit animal before straying into the North Sea and then the Thames.

However, there were questions about how long the whale was allowed to remain in the river and how long she was on the rescue boat.

"This may be the first Northern bottlenose whale rescue in history, and there's nothing in the textbook to tell us how long they can stay out of water," Jepson said.

"We didn't want to leave her on the boat for too long. We just wanted to get her out as far as we could. But her condition rapidly deteriorated and we made the decision to euthanize her. When I was actually drawing the lethal injection, she died."

Becki Lawson, a wildlife veterinarian with the Zoological Society, added: "Really, we all felt that everything that could be done to save the whale had been done."

The British Divers Marine Life Rescue volunteer group spent at least $9,000 on the rescue and is hoping to raise funds for future efforts through an Internet auction of the watering can used to moisten the whale's skin.

The whale's remains have gone to the Natural History Museum, where they will be available to researchers.