Wildlife advocacy groups are suing to force the U.S. government to look again at whether the hunting and slaughter of bison that wander outside of Yellowstone National Park threaten the survival of one of the last genetically pure populations of the national mammal.

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. They are asking a judge to order federal wildlife officials to re-examine whether the Yellowstone bison should be listed as a threatened or endangered species.

Bison, which Congress designated as the national mammal earlier this year, were hunted to near extinction in the late 19th century. The estimated 4,900 Yellowstone bison are one of the last remaining populations in the U.S. that don't have cattle genes in their DNA.

The Fish and Wildlife Service earlier this year rejected two petitions seeking federal protections for Yellowstone bison that would prevent them from being hunted, rounded up for slaughter or hazed back into the park when they leave in search of food.

Federal wildlife officials said in rejecting the petitions that Yellowstone bison numbers are stable and growing, and there is no scientific information that would lead to their being considered threatened or endangered.

A consortium of federal, state and tribal officials that manage the bison aims for a population of about 3,000. The Interagency Bison Management Plan calls for decreasing the existing population through hunting outside of the park's boundaries and capturing them for slaughter, relocation or research.

In the lawsuit, the wildlife groups say the Yellowstone bison numbers are too few, they lack genetic diversity and they are confined within a small portion of its historical range.

"It's not a viable population," said Friends of Animals' wildlife law program director Mike Harris. "There's too much inbreeding and they're subject to population collapse if disease hits the herd or there is a change in habitat due to drought or climate change."

The wildlife groups are asking a federal judge to order the government to withdraw its rejection of the petitions seeking to list Yellowstone bison as endangered or threatened, and to issue a new finding within 60 days of the court's order.

Yellowstone officials did not return calls for comment.

Park biologists have said the bison population needs to average between 3,000 and 5,000 animals to preserve genetic diversity, according to the Interagency Bison Management Plan. Park officials have also said that the bison population has grown steadily from 500 animals in 1970 to the current numbers, and culling the herd does not put the population at risk.