CHEYENNE, Wyo. (AP) — The federal government is preparing to launch a new round of research into ways to prevent wild horses and burros from overpopulating Western rangelands.

The U.S. Bureau of Land Management this week announced 21 research projects involving wild horses and burros. Among them is new research to improve the effectiveness of contraceptive drugs for wild mares. The studies will cost a total of $11 million over five years. The BLM says fewer people these days are adopting wild horses through the agency's roundup program.

BLM spokesman Jason Lutterman said Friday the new research seeks to develop a variety of methods in addition to roundups to control the animals' numbers. The West has some 58,000 wild horses and burros. Many of those animals have overpopulated the rangelands where they live.