Criticism of roundups is not limited to wild horses. In this video, wild burro advocates document "aggressive" roundup practices.

Public criticism of roundups is not limited to wild horses. The Bureau of Land Management also conducts annual “gather” operations to remove “excess” wild burros from herd areas in the West.

In this video, advocates for the wild burros document "aggressive" roundup practices, including a helicopter hitting and flipping over a burro in the California desert in 2009 and a BLM contract wrangler manhandling a reluctant burro during a 2008 roundup in Arizona.

As with the wild horse roundups, the BLM defends the operations as humane and says that incidents such as these are both isolated and contrary to its contractor guidelines.

The BLM says there are about 5,800 wild burros living in the wild, mostly in Arizona, Nevada and California, but many advocates believe the wild burro population is much smaller and that burro roundups are unnecessary.

Lisa Myers is NBC News' Senior Investigative Correspondent; Michael Austin is a producer in NBC's bureau in Burbank, Calif.

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