A jump in the wolf pup survival rate helped spark a 20 percent increase in the Southwest's Mexican wolf population last year, federal officials said.

Aerial and ground-based surveys late last year found 50 wolves - 29 in Arizona and 21 in New Mexico, U.S. Fish and Wildlife Service officials said Tuesday. The service released two wolves into the wild last month that weren't counted.

A year ago, the count was 42, the lowest since 2002.

The 2009 count triggered alarm among service officials and environmentalists. It represented a long-term decline from the record high wild wolf population of 59 reached in 2006.

The federal wolf recovery program's goal is a wild population of 100.

In 2010, 14 of 18 newborn pups survived, compared with seven surviving pups out of 30 born in 2009. The 2010 population also weathered six wolf deaths, five from illegal shootings.

While calling the new count encouraging, Wildlife Service Regional Director Benjamin Tuggle acknowledged that authorities don't know enough about what's going on in the wild to be assured a precipitous drop won't happen again.

Some of the higher pup survival rate can be traced to supplemental feeding of deer, elk and horsemeat to pups in packs whose alpha males were shot, said Maggie Dwire, the service's assistant wolf recovery coordinator. An alpha male is the lead wolf in a pack.

Supplemental feeding is "not a practice we really love to use," service spokeswoman Charna Lefton said.

Contact reporter Tony Davis at tdavis@azstarnet.com or 806-7746.