The National Academy of Sciences was asked to study what health threats wild buffalo pose to cattle in hopes of resolving a dispute that has seen more than 1,000 bison killed near Yellowstone National Park this winter. Interior Secretary Bruce Babbitt said he wants the academy to report back by October. State officials in Montana have defended the shooting of buffalo that wander outside Yellowstone because many of them carry the bacteria brucellosis, which causes cows to abort their calves. There is no vaccine for the disease in wild animals. Babbitt called the buffalo killing "an overreaction and unnecessary." because he said there are no cattle in the area of a federal forest where the buffalo have been wandering for forage. There has never been a recorded transmission of brucellosis from a wild buffalo to a cow, government biologists say.