In a letter released by environmental groups Wednesday, the government says it will further study whether their actions violate the Endangered Species Act.
Wildlife Services, part of the U.S. Department of Agriculture, intentionally killed 400 beavers in Oregon in 2016 because of concerns the animals were building dams that flooded agricultural fields and hurt timber land.
The animals can also cause flooding around culverts that can impact road stability.
The Western Environmental Law Center, Center for Biological Diversity and Northwest Environmental Advocates say beaver dams provide critical habitat for young salmon, coho and steelhead.
Those species benefit from deep pools created by the dams.