The USDA’s Wildlife Services’ (WS) National Wildlife Research Center (NWRC) announced Feb. 13 that the U.S. Environmental Protection Agency (EPA) has granted regulatory approval for the use of an equine immunocontraceptive vaccine (GonaCon-Equine) in adult female wild or feral horses and burros. GonaCon was developed by NWRC scientists and is the first single-shot, multiyear wildlife contraceptive for use in mammals.

"Since 2009, GonaCon has been available for use in female white-tailed deer," said NWRC Director Larry Clark. "We are pleased to be able to expand the vaccine’s application to include wild horses and burros. This nonlethal tool will provide another option to wildlife managers working to reduce overabundant wild horse and burro populations in the United States."

The Bureau of Land Management (BLM) estimates that approximately 37,300 wild horses and burros (about 31,500 horses and 5,800 burros) roam on BLM-managed rangelands in 10 Western states. The estimated current free-roaming population exceeds by nearly 11,000 the number that the BLM has determined can exist in balance with other public rangeland resources and uses. Current management options are limited with the majority of actions involving the removal of horses and burros from the range and either offering them for adoption or holding them indefinitely in captivity. The BLM estimates there are more than 49,000 wild horses and burros off of BLM-managed lands that are fed and cared for at short-term corrals and long-term pastures.

The GonaCon-Equine vaccine stimulates the production of antibodies that bind to the gonadotropin-releasing hormone