Wildlife advocates and environmental groups are challenging the removal of federal protections for gray wolves across most of the U.S.
Two coalitions of groups have filed notice that they plan to sue the U.S. Interior Department in federal court unless protections are restored.
The Trump administration last week ended longstanding federal safeguards for gray wolves in the Lower 48 states. That put states and tribes in charge of overseeing the predators and opens the door to more hunting.
Gray wolves have recovered from near extinction in parts of the country but remain absent from much of their historical range. Colorado wildlife officials plan to reintroduce wolves in coming years.