Roundups are necessary for the Bureau of Land Management (BLM) to control population growth among wild horse herds, according to a report by the Department of the Interior's Office of the Inspector General (OIG).

In the report issued on Dec. 13 the auditors also called on the BLM to be more aggressive in researching and testing approved science for population control methods to minimize the need for long-tern holding facilities and mustang preserves.

The Wild Free-Roaming Horse and Burro Act of 1971 designates wild horses and burros as an integral part of the national public land system and places the BLM in charge of the animals' management. According to BLM estimates, 33,700 wild horses currently roam agency-managed rangelands in 10 western states. Another 37,000 animals currently reside at short-term holding corrals and long-term pastures.

The Act also charges the agency, which is a division of the Department of the Interior, with maintaining the natural ecological balance of authorized uses of federal lands. In order the achieve the balance, the Act directs the BLM to inventory animals residing on public ranges, and authorizes the agency to remove excess animals on overpopulated ranges and to relocate removed animals to holding facilities where some might be culled out for sale or adoption