The Mexican gray wolf has rebounded to its highest numbers in the American Southwest since its near extinction a half-century ago—to the delight of environmentalists but angst of some ranchers.

Considered the most endangered of the world’s wolf species, the Mexican gray wolf disappeared from its native habitat in the southwestern U.S. and northern Mexico in the 1970s due largely to hunting and trapping. They remained out of the wild until 1998, when 11 wolves raised under a captive breeding program run by the U.S. Fish and Wildlife Service were released in the mountains of eastern Arizona.

Since then, the Mexican gray wolf has been on an upward trajectory—reaching a record 163 in the Southwest in 2019, 24% higher than the previous year and the 10th straight year of increases, according to the Mexican Wolf Interagency Field Team, a task force of various government agencies.

Federal wildlife officials say the higher numbers come after recovery efforts that have included placing captive-born pups in dens to be raised by wild adults and expanding areas where the animals are released. The wolves now mostly inhabit a mountainous region on the border of Arizona and New Mexico, living in 42 different packs.

“This is really encouraging news at a time when we all need some encouraging news,” said Bryan Bird, Southwest program director for Defenders of Wildlife, an environmental advocacy group. “It’s a pleasant surprise to see the population increase by this much.”