The report, published in the journal Oryx, said there have been no confirmed jack rabbit sightings in Yellowstone since 1991 and only three in Grand Teton National Park since 1978.

Historical records indicate that white-tailed jack rabbits were once abundant in Greater Yellowstone, a 23,166-square-mile ecosystem that contains the Grand Teton and Yellowstone national parks, the group said Thursday in a release.

Lead author Joel Berger of the University of Montana said the lack of jack rabbits could be due to disease, extreme weather, predation or other factors.

"Since the rabbits blipped off without knowledge, there has simply been no way to get at the underlying cause," he said in a statement.

Berger said the the absence of jack rabbits may be causing elevated predation by coyotes on juvenile elk, pronghorn and other ungulates and suggests that wildlife managers should consider reintroduction of the rabbits.

"Reintroduction may result in the establishment of dynamic ecological processes that were intact before rabbits vanished from the ecosystem," he said.