The Humane Society of the United States and other groups are suing to restore federal protections for wolves in the western Great Lakes region.
The groups filed the lawsuit in federal court in the District of Columbia on Tuesday against the U.S. Fish and Wildlife Service.
They say taking wolves in Minnesota, Wisconsin and Michigan off the endangered list last year threatens the recovery of wolves throughout most of their historic range.
Hunters and trappers in Minnesota and Wisconsin killed over 500 wolves during those states' recently concluded seasons. The Michigan Legislature voted in December to authorize the resumption of wolf hunting.
The Humane Society of the United States provided a copy of the lawsuit to The Associated Press ahead of a public announcement.