The North American beavers’ greatest strength, their industrious dam building, benefits the ecosystem as well as conflicts with human infrastructure. In Oregon, the semiaquatic rodent is the state animal and Oregon State University’s mascot. It also holds dual status under state law that classifies it as a predator on private lands and fur-bearing game species on public lands.

This means private landowners may control beavers causing damage by killing trees and plugging culverts and irrigation ditches without requesting permission or reporting the control. If trappers want to harvest a beaver from public land, they must apply for a permit from the Oregon Department of Fish and Wildlife and report their take. Additionally, the USDA Animal and Plant Health Inspection Service’s Wildlife Services division controls beavers, at the request of stakeholders, when in conflict with human health and safety.

On Nov. 2, a coalition of environmental groups filed notice to sue Wildlife Services over its aquatic mammal damage management program. These groups — the Center for Biological Diversity, Northwest Environmental Advocates and Western Environmental Law Center — state that Wildlife Services’ control of beavers is without analysis of impacts to threatened and endangered wildlife. These threatened species include steelhead trout, Oregon coast coho salmon and Oregon spotted frog, which the groups say benefit from the riparian habitat and water impoundments created by beavers’ dams.

In 2016, USDA APHIS Wildlife Services reported that it controlled 403 beavers. In comparison, in the most current data publicly available (2014), ODFW reports 1,976 beavers were harvested by fur takers. While ODFW describes the state’s population of beavers as healthy and abundant, the concerned environmental groups estimate it at 3% to 10% of historic levels.

No data available
In reality, there aren’t comprehensive data on current or historic beaver population, notes Jimmy Taylor, a courtesy faculty member in Oregon State University’s Department of Forest Ecosystems and Society and an expert in beaver-conflict prevention for APHIS.

“I think it would be really nice to know how many beavers are out there,” Taylor says. “Beavers are one of the hardest wildlife species to survey because they’re often in bank dens instead of lodges, and not all beavers build dams. These are the classic signs that most people associate with beavers. Just because you don’t see a beaver dam or lodge does not mean beavers are not there."

He explained that beavers are also nocturnal, active under forest canopy, and move around according to water and forage availability. That makes aerial estimates of dams, lodges, ponds or food caches impractical. You have to walk banks and/or float the water looking for all possible beaver signs to confirm or deny their presence.

Under threat of the lawsuit, Wildlife Services responded on Dec. 27 by ceasing all aquatic mammal damage management activities in Oregon related to damage caused by beaver, river otter, muskrat and mink until a compliance review of the Endangered Species Act is completed.

Taylor said he definitely would do a statewide beaver population survey to inform management decisions if research funding was available. In the meantime, he will continue to research and educate people about the role beavers play in forests, on agricultural lands and across watersheds — as well as where to expect human conflicts with beavers to occur, and the best mitigation practices.

“It all helps improve management of lands and wildlife,” Taylor adds. “Hopefully, research will help guide policy decisions, so we can manage things in the best way possible.”

Hemken writes from Lander, Wyo.