PHOENIX — Endangered Mexican gray wolves rebounded from a deadly 2015 to reach a population of 113 in eastern Arizona and western New Mexico last year, the most since the species returned to the wild almost 20 years ago, federal and state biologists announced Friday.

The population of wolves, first reintroduced from captive breeding into the two states in 1998, had grown by fits and starts to 110 two years ago before dropping back to 97 at the end of 2015. Unsolved illegal shootings contributed to the losses, and officials said that year also saw lower pup survival.

Last year was different, according to winter ground and aerial surveys conducted by the U.S. Fish and Wildlife Service and its partner wildlife agencies in the two states. Fifty wild-born pups survived the year, compared with just 23 in…