HELENA, Mont. (AP) — Wildlife advocacy groups are suing to force the U.S. government to study whether the hunting and slaughter of bison that wander outside of Yellowstone National Park threaten the animal's survival.

Buffalo Field Campaign, Western Watersheds Project and Friends of Animals filed the lawsuit against the Interior Department and the U.S. Fish and Wildlife Service Monday in U.S. District Court in the District of Columbia. The groups are asking a judge to order federal wildlife officials to study whether the Yellowstone bison should be listed as a threatened or endangered species.

They say the Yellowstone bison population is too small, lacks genetic diversity and is confined within a small portion of its historical range. There are approximately 4,900 Yellowstone bison. Yellowstone officials have said culling the population does not put the population at risk.

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