Only three wolves — a male, a female and a 9-month-old pup — remain in Isle Royale National Park in Michigan, where wolves have been studied for nearly 60 years. Researchers first noticed their numbers declining in 2009, possibly because of inbreeding. The population will probably not recover naturally, biologists have concluded. The pup appears to be sickly, with a constricted waistline, hunched posture and a deformed tail. The wolves prey on moose, whose population is on the rise. More than 1,000 have been spotted on the island.