Horses at the Bureau of Land Management adoption center in Pauls Valley, Oklahoma, has started using a new contraception vaccine that officials hope will prevent horses from conceiving for up to five years.
Without contraception, the wild horse population grows about 20 percent a year, according to the BLM.
The hope is that the long-term vaccine will work and the wild horse population will fall, BLM spokesman Paul McGuire said.
The study covers 90 mares that have been treated with either vaccines or a placebo, according to the BLM. Reproduction isn’t allowed at BLM facilities, but for this study, the mares will live among males. Officials will track their reproduction for five years.
“The core issue is that horses can easily overpopulate the range that they inhabit,” McGuire said. “Management is critical.”
There are more wild horses and burros in government-funded private pastures than are roaming on the Western range, according to the BLM. About 41,000 wild horses and burros live in short- and long-term holding pastures. About 38,000 roam free on the range.
A longer-lasting vaccine would cut the agency’s costs and reduce the number of times horses come into human contact.
“The horses really need to be left alone, and that is the whole intent,” McGuire said. “Let these horses live as wild, free-roaming animals with minimal invasive management.”