ALBUQUERQUE, N.M. -- There are now more Mexican gray wolves roaming the American Southwest than at any time since the federal government began reintroducing the endangered predators.
An annual survey released Friday by the U.S. Fish and Wildlife Service shows at least 109 wolves are spread among forested lands in southwestern New Mexico and southeastern Arizona.
The population is more than double what it was in 2010. Last year, the survey turned up at least 83 wolves.
Fish and Wildlife Service Regional Director Benjamin Tuggle described the increase as a monumental milestone that has resulted from a combination of management changes made in recent years, experiments such as cross-fostering pups among different wolf packs and more social tolerance for the animals.
"We don't have the total formula. But we have what we think are the key elements for success, so we're trying to move forward," Tuggle said during a conference call.
A subspecies of the gray wolf, the Mexican wolf was added to the federal endangered species list in 1976. It wasn't until 1998 that the first captive-bred wolves were released into the wild.
The reintroduction effort has been hampered by politics, illegal killings and other factors. Disputes over management of the program have spurred numerous legal actions by environmentalists who want more wolves to be released and by ranchers concerned about their livelihoods and safety in rural communities.
In December, the Fish and Wildlife service announced a large expansion to the area wolves are allowed to roam, which officials say should allow the wolf population to continue growing.
Tuggle pointed to efforts to interact more with ranchers, methods for limiting livestock kills by wolves and a compensation program aimed at easing the economic consequences of wolf predation.
"We very clearly knew from the very beginning that we couldn't get along strictly with the biology," he said. "The social tolerance part is absolutely critical."
Despite the increase in wolf numbers, federal wildlife officials are still concerned about ensuring genetic diversity. Inbreeding can cause a number of problems, including low survivability among pups.
Officials said 2014 marked one of the most successful years, with 38 pups surviving at least through the end of the year. That's compared to only 17 in 2013.
While biologists documented 19 packs between Arizona and New Mexico, there were only eight breeding pairs.
"While overall numbers are important, this is somewhat worrisome," said Michael Robinson of the Center for Biological Diversity. "This is a narrow base for the future. Breeding pairs give us insight into the potential for growth of the population."
Jim DeVos, an assistant director with the Arizona Game and Fish Department, said the latest survey is good news when considering there wasn't a single wolf on the landscape in 1997. In fact, a Mexican gray wolf hadn't been seen in the Southwest since 1970.
"It's such a tremendous step in the right direction to recovery an iconic species," he said. "This type of recovery in a working landscape is certainly incredible and it bodes well for the future."
The population now consists of four generations of wild-born wolves. More than half of them are outfitted with collars so managers can track and monitor their activities, federal officials said.