PHOENIX — The Sonoran pronghorn native to Arizona was on the cusp of extinction in the United States with 21 individuals in the wild in 2002, according to the U.S. Fish and Wildlife Service.

A binational effort between the U.S. and Mexico launched a semi-captive breeding program in Arizona in 2004 to restore a healthy pronghorn population north of the border.

Arizona Game and Fish Department was allowed to translocate six animals to a captive breeding pen at Cabeza Prieta National Wildlife Refuge in Ajo.

Nearly 20 years later, the program and other actions taken federally and by the state have led to a Sonoran pronghorn population increase to an estimated 456, a significant leap from the 80-90 animals in 2010, according to the AZGFD.

Six pronghorn — after they were given medical evaluations and fitted with GPS collars — were released back into the wild in Mexico on Jan. 10 after a stint in northern Sonora’s El Pinacate Biosphere Reserve.

“The road to delisting and full recovery is an ongoing process, but there is no doubt that past and present collaborative efforts have resulted in positive outcomes,” Cynthia Soria, AZGFD’s international and borderlands wildlife specialist, said in a press release.

We are thrilled to have worked with the Arizona Antelope Foundation and @azgfd to take down a temporary holding pen for endangered Sonoran pronghorn in the Sonoran Desert National Monument. The hope is that this group will join another resident herd in the area. pic.twitter.com/DpjoWSRTqs

— Arizona Wildlife Federation (@AZWildlifeFed) February 3, 2023

The Sonoran pronghorn (Antilocapra americana sonoriensis) — one of five subspecies of the American pronghorn — is still listed as endangered by the USFWS, but the return of the six animals to Mexico was a declaration by the AZGFD that Arizona’s population is sustainable.

When the captive breeding program began, an agreement was made that Arizona would return six pronghorn back to Sonora once a sustainable population was established.

The species was first listed as endangered in 1967 by the precursor of the Endangered Species Act.

Threats to pronghorn have been drought, wildfires, highways and man-made obstacles to food and water resources, hunting, poaching and clearing for agriculture, according to the USFWS.

Management projects are ongoing, as the AZGFD released nearly 30 animals from the USFWS Buenos Aires National Wildlife Refuge in Pima County, which doubled the size of the local heard, on Jan. 24.

Since the start of the breeding program, approximately 400 pronghorn have been translocated to the Kofa National Wildlife Refuge, Vekol Valley and the Barry M. Goldwater Range.

The Comision Nacional de Areas Naturales Protegidas, El Pinacate Biosphere Reserve, Comision de Ecologia y Desarrollo Sustentable del Estado de Sonora, the National Park Service and the Bureau of Land Management were among agencies to assist in brining the six pronghorn back to Mexico.