A conservation group says the federal government hasn't done enough to save Mississippi's endangered burrowing frogs because it has no rescue plan. The Center for Biological Diversity's legal notice of plans to sue comes about three months after a property rights group said it will sue because the Interior Department has gone too far in protecting dusky gopher frogs. About 100 live in the wild. Zoos have fewer than 900. Attorney Collette Adkins Giese says she wants the government to set a deadline for creating a recovery plan within the 60 days before her group may sue. The U.S. Fish and Wildlife Service says litigation has held back work on a recovery plan but biologists are pleased with what's been done and optimistic about future work.