A jackrabbit found throughout much of the West has disappeared from the Yellowstone area, although the reason why remains a mystery, a new study concludes. Whatever the cause, the study suggests the white-tailed jackrabbit's disappearance has wrought major changes to Yellowstone's food chain. Coyotes and wolves, which could have depended on the rabbit as a significant food source, apparently turned their attention instead to larger prey including young elk, pronghorn antelope -- even domestic livestock. However, because the rabbit's decline went relatively unnoticed until now, quantifying that shift is virtually impossible, said the study's lead author, Joel Berger with the...