Federal wildlife officials have designated 6,200 acres in coastal Alabama and the Florida Panhandle as critical habitat for three endangered beach mouse species.
Property owners or developers could be required to survey property for the protected mice before construction or to redesign a project that would harm the nocturnal creatures, according to the U.S. Fish & Wildlife Service.
Beach mice are an indicator of the health of the dunes, since they live inside the mounds of sand near the water's edge. The mice take seeds and acorns into the dunes, which sometimes sprout and grow, leading some scientists to believe the mice may help keep the dunes stable.
The acreage, most of it in Florida, includes a mix of federal, state park and private land.
The wildlife service estimates the cost of saving the three subspecies of beach mice at $93.4 million to $174.9 million over the next 20 years, nearly all of that in costs paid by landowners or developers who must alter or restrict their beachside projects.
"It's based on the amount of expected development in beach mouse habitat over 20 years and the cost to developers," said Janet Mizzi of the Panama City, Fla., wildlife service office. "And we do expect considerable development."
The subspecies protected by the decision are the Perdido Key beach mouse, which is native to Alabama, and the Choctawhatchee and St. Andrew beach mouse.
The new critical habitat is broken into 13 units in Alabama's Baldwin County and Florida's Bay, Escambia, Okaloosa and Walton counties.
A critical habitat is an area that the FWS finds essential for the conservation of an imperiled species. It can include land where the species is not now living but would need as its population recovers and grows.