MEXICO CITY — The first known litter of Mexican gray wolves has been born in the wild as part of a three-year effort to re-introduce the subspecies to a habitat where it disappeared three decades ago, Mexican officials reported Thursday.Mexico's National Commission for Natural Protected Areas said the wolf pups were sighted in June by a team of researchers in the western Sierra Madre mountains."This first litter represents an important step in the recovery program, because these will be individuals that have never had contact with human beings, as wolves bred in captivity inevitably do," the commission said in a statement.It said the pups appeared to be doing well.Mexico began reintroducing wolves in 2011, and the parents of this litter had been released in December with hopes they would reproduce. Authorities seldom reveal the exact location of breeding pairs in recovery programs, to protect endangered species.The commission did not respond to requests about how many wolves now live in the wild in Mexico.The Mexican gray wolf was almost wiped out in the U.S. Southwest by the same factors that eliminated it in Mexico: hunting, trapping and poisoning.The last five survivors in the U.S. were captured between 1977 and 1980, and then bred in captivity. The first wolves were re-introduced into the wild in the Southwest starting in 1998, mainly in Arizona and New Mexico.The Mexican gray wolf remains an endangered species in the United States and Mexico.But a U.S. Fish and Wildlife Service annual survey released in January showed there are at least 83 of the endangered predators in Arizona and New Mexico, marking the fourth year in a row the population has increased.