Park managers say the change is intended to control disease, rather than population. A massive elk-reduction campaign in Yellowstone in the 1960s resulted in national outrage (HCN, 9/15/97). Rangers will act only as a last resort when the animals seem intent on leaving the park and can't be chased back, says park spokeswoman Cheryl Matthews. "They're going to have to have one foot out of the park before we resort to that."
Bison are a target along Yellowstone's northern boundary because some may carry the disease brucellosis, which can cause domestic cattle to abort their calves. Park managers agreed as part of a legal settlement with the state of Montana to kill bison exiting the park, although there is no proven case of wild bison passing the disease to cattle.
* Michael Milstein