By Laura Zuckerman
The southwestern US population of endangered Mexican grey wolves declined by 12 percent last year after five years of steady growth, leading wildlife advocates to suggest that illegal killings of the beleaguered predators may be to blame.
Wildlife managers said on Thursday (local time) the drop -- from 110 wolves in 2014 to 97 last year -- was unexpected and disturbing.
The tally did not include an estimated 20 more Mexican wolves roaming south of the US border.
"The lower number of Mexican wolves that were counted is a concern, but not a signal that the program is unsuccessful," Jim de Vos, assistant director of wildlife management for the Arizona Game and Fish Department.
The US population of the Mexican wolf, the rarest subspecies of grey wolves in North America, had been gradually expanding over the previous five years, averaging 11 percent annual growth in southern New Mexico and southeastern Arizona, said John Bradley, spokesman for the US Fish and Wildlife Service.
Factors that led to last year's decline include the deaths of 13 wolves, nine of them females, and a sharp decrease in the number of wolf pups that survived through December, government wildlife managers said.
Mexican wolves were believed to be all but extinct in the United States and Mexico when the last five were caught alive in Mexico between 1977 and 1980 and used for a captive breeding program that saw 11 animals released to the wild in the two southwestern US states in 1998.
Like their larger counterparts in the Northern Rockies and the US Midwest, Mexican grey wolves draw the ire of ranchers for preying on cattle and are a big game prized by hunters.
The wolves were once hunted, trapped and poisoned to near extinction before coming under US Endangered Species Act protections in the 1970s.