By Scott Sonner, AP

The Bureau of Land Management has pulled the plug on a public-private partnership in Nevada aimed at shrinking the size of a wild horse herd southeast of Carson City through the use of contraceptives.

Unlike most mustang conflicts pitting protection groups against ranchers, the dispute in Nevada’s Pine Nut mountains is fueled largely by a division among horse advocates themselves over the use of fertility drugs on the range.

BLM approved a pilot project in 2014 working with the American Wild Horse Preservation Campaign and a neighborhood group to treat a herd that a federal judge has forbid the agency from gathering.

But an internal email obtained by the Associated Press shows BLM suspended the project Monday after leaders of Friends of Animals threatened to sue. That group says the drug harms horses and violates the judge’s order.