PORTLAND, Ore. — The U.S. government will temporarily stop killing beavers in Oregon after environmental groups threatened a lawsuit alleging the practice reduces the number of dams that create deep pools that are ideal habitat for young, endangered coho salmon.

In a letter released Wednesday by a coalition of environmental groups, the government said it will further study whether the actions violate the Endangered Species Act.

Wildlife Services, a branch of the U.S. Department of Agriculture, said in the Dec. 27, 2017, letter that it would "cease all aquatic mammal damage management activities" directed at beavers, river otters, muskrats and mink.

Wildlife Services killed more than 400 beavers in Oregon in 2016 as part of a federal effort to control damage to agricultural fields, timber land and roadways caused by flooding that resulted from beaver dams.

It's a little-known program in Oregon, where the beaver is the state animal, appears on the state flag and is the mascot of Oregon State University. Beavers played an important role in the state's early economy, earning Oregon the nickname "the beaver state."

Environmentalists say killing beavers to mitigate damage to private agricultural interests harms the environment and particularly endangered salmon species because the dams help salmon - another icon of the Pacific Northwest.

Beavers are "nature's engineers" and their complex dams form deep pools in bubbling streams that shield young salmon and give them a resting place to fatten up as they migrate to the Pacific Ocean, said Andrew Hawley, a staff attorney with the Western Environmental Law Center.

The dams have also been shown to reduce turbidity in streams and maintain stable water levels even in drought by blocking and slowing the flow of water.

"Instead of going in and just killing them, there are options for live-trapping them and figuring how to move the family units into other areas. Let them do what they do best," he said.

"They do exactly the type of restoration work that the biologists say we need to do for salmon and coho and steelhead recovery and they do it for free - and better than we could ever do."

A message and email left for David Williams, state director of the Wildlife Services program in Oregon, were not returned Wednesday.

Beavers are the largest rodent in North America. They can grow to four feet in length and reach 65 pounds.

They build dams to create ponds in fast-moving streams and then build a lodge of felled trees in the middle of the pond. The lodges have underwater entrances and the beavers - which can hold their breath for 15 minutes underwater - enter and exit without attracting attention from predators.