The New Mexico-based Wild Earth Guardians filed suit this week and the Tucson-based Center for Biological Diversity has given notice it intends to sue the U.S. Fish and Wildlife Service for failing to meet a legal deadline for deciding whether to propose the Mexican gray wolf as an endangered species, separate from other gray wolf subspecies. Currently, all gray wolf populations in the United States are classified as a single endangered species.

The service concluded over the summer that the Mexican wolf may warrant separate protection as endangered but failed to meet a deadline to decide on a formal proposal, the groups said. The groups want the Mexican wolf listed separately, so the service will be required to prepare a recovery plan for the species.