The sad final verdict is in: Celebrity polar bear Knut died from drowning. But the four-year-old's collapse into his enclosure's pool at the Berlin Zoo was caused by encephalitis, according to a necropsy performed on the bear. The AP reports that a zoo pathologist said she could not tell what caused the encephalitis—a swelling of the brain likely brought on by an infection—but ruled out rabies, botulism, and mad cow disease. Even if Knut had not drowned, the damage from the brain swelling would have killed him, reported the pathologist.
Some animal rights groups have tried to blame Knut's death on stress caused by living in a zoo, but the pathologist said there were no signs stressed played any part. Knut was rejected by his mother at birth in December 2006, and was raised instead by zookeepers, soon becoming an animal celebrity at the zoo. (Read more Knut stories.)