By the mid-1990s, for instance, nearly all the fishers — a weasel-like animal — were eliminated from Mount Rainier National Park. Experts reintroduced 10 of them back into the wilderness in 2016. Other animals had been run out of town, too. But as the researchers discovered, one appeared to be making a comeback. Photo credit: U.S. Fish and Wildlife Service / WikiCommons / Attribution 2.0 Generic