RENO, Nev. (AP) — Wild horse advocates are united in their belief the animals should remain free to roam public rangeland across the West.

But they are at odds over whether contraception should play a role in managing the size of the herds. The American Wild Horse Preservation Campaign, which includes the Humane Society of the United States and dozens of other groups, has been willing to accept treating mares with the anti-fertility drug PZP as a more humane alternative to shipping mustangs to holding facilities.

Leaders of two dissenting groups who recently won a court order blocking a roundup in Nevada are critical of the national coalition. They accuse some members of abandoning the mustangs' best interests. Friends of Animals and Protect Mustangs say studies show the contraceptive is disrupting the herds' social structure.