Federal officials issued regulations Wednesday designed to protect the northern long-eared bat, one of several types of bat that have suffered steep population declines because of a rapidly spreading fungal disease.

The U.S. Fish and Wildlife Service said it had updated interim rules that accompanied a decision last April to designate the northern long-eared bat as threatened under the Endangered Species Act. The final version is less restrictive toward timber harvesting, clearing land for wind turbines, houses or oil pipelines and other activities that might cause some bats deaths but have no significant effect on the overall population, agency director Dan Ashe said.

It drew praise from an industry group, but a lawsuit warning from environmentalists who said it would make things worse for a species whose numbers have fallen more than 90 percent in some places.

The policy will enable the government to focus its bat conservation efforts primarily on white-nose syndrome, which has killed some 5.7 million of the winged mammals since its discovery in a New York cave in 2006, Ashe said. The disease or the fungus that causes it have been detected in 30 states in the Northeast, South and Midwest and in five Canadian provinces. Seven bat species have been affected, and the northern long-eared is among those hardest hit.

"Until there is a solution to the white-nose syndrome crisis, the outlook for this bat will not improve," Ashe said. "This rule tailors regulatory protections in a way that makes sense and focuses protections where they will make a difference for the bat."

The fungus attacks bats that spend winters in caves and mines, disrupting hibernation and depleting the energy their bodies must ration until spring to avoid starvation.

Bats are valuable to people, eating mosquitoes and other insects that otherwise would cause billions of dollars in crop damage.

The Fish and Wildlife Service decided against listing the northern long-eared bat as "endangered," or nearly extinct, settling for the category of "threatened," which imposes less-stringent limits on human actions that could harm the animal.

Even so, the ruling drew criticism from the timber and oil and gas industries, which said it could boost costs and hamper their work without measurably helping the bats. The federal agency received more than 40,000 public comments. Officials said the regulations, which take effect Feb. 16, are necessary to protect crucial habitat, including hibernation caves and trees where the bats raise their young during summer.

But the rules were revised to reduce inconvenience to landowners and industry, said Tom Melius, the service's Midwestern regional director. While making it illegal to intentionally kill or harass the bats, they keep to a minimum the prohibitions on harm that happens during otherwise legal projects.

In areas where white-nose syndrome exists, such "incidental" harm is illegal at hibernation sites and as a result of removing trees within a quarter-mile of those sites. Also protected are trees where bats give birth and roost—and other trees within 150 feet of them—during June and July, when pups are in nests and haven't learned to fly.

The Independent Petroleum Association of America said the final regulations were a "workable compromise."

"While oil and gas operations have a negligible impact on the health of the northern long-eared bat, independent producers stand willing and able to comply with conservation measures designed to protect the bat during its most sensitive stages of life," said Dan Naatz, a vice president of the trade group.

The Center for Biological Diversity is challenging in federal court the interim rules and the government's refusal to list the bat as endangered. The environmental group may expand the suit to include the new rules, which "will almost certainly result in more dead bats by allowing the destruction of habitat they need when coming out of hibernation or are pregnant in the summer," attorney Tanya Sanerib said. "It's the last thing they need after being devastated by disease."