Columbian white-tailed deer make gains, but still face threats, challenges

Altered habitats

Columbian deer are peppered between multiple subpopulations living in Wahkiakum, Cowlitz and Clark counties in Washington, and Clatsop, Columbia and Multnomah counties in Oregon. The most populous group lives around Ridgefield.

Meadows and forests with an abundance of deciduous trees are ideal habitats for the deer. Here, the animals graze on grass, sedges and forbs while remaining close to streams protected by canopy cover.

Historically, much of this habitat was lost through land use by humans, whether through agriculture, forestry or urbanization. As a result, the deer moved into divided pockets of lowlands and floodplains.

These environments aren’t ideal for deer due to flooding, which is a growing threat as sea levels continue to rise. The Washington Coastal Hazards Resiliency Network projects sea levels at the Columbia River’s mouth could rise two feet by 2100.

Although the Columbia River floodplains upriver won’t experience the brunt of this, there will be noticeable effects in areas closest to the estuary, Azerrad said. Furthermore, soil that encounters frequent flooding is likelier to host necrobacillosis, an infection that could cause disease and potential death in deer.

Wildlife officials are strategizing how to move the deer away from the floodplain to protected areas, which leads into another issue: connectivity.

Habitat vs. development

The city of Ridgefield’s human population has grown about 14.5 percent between 2021 and 2022, according to an estimate from the Washington State Office of Financial Management. With the new residents has come a wash of development, with more projected to come.

Expanding networks of busy highways, urbanization and converted conifer forests reduces deer’s ability to join other subpopulations. Azerrad said connectivity is valuable for the survival of the species because it leads to healthy reproduction, as opposed to inbreeding that could result in genetic issues.

Ian Sinks, Columbia Land Trust stewardship director, said the organization — a partner in deer and general wildlife conservation — has procured hundreds of acres of land to restore habitats, such as the Columbia Stock Ranch on Deer Island. Projects in these areas specifically touch on replanting native vegetation, which may in turn expand Columbian deer ranges.

“It’s about making secure and quality habitats,” Sinks said.

Columbian white-tailed deer have been considered an endangered species since 1967, when they were federally listed.

At that time, about 450 white-tailed deer lived in Washington and Oregon. After scientists engaged in preservation work, the population jumped to 900 nearly 40 years later, leading to the species being federally down-listed to threatened in 2016.

A mix of state, conservation group and tribal initiatives helped reestablish the deer population, such as tagging and tracking deer, restoring habitats and controlling predation. A decade ago, some of the deer from the Julia Butler Hansen National Wildlife Refuge near Cathlamet were transplanted to join the Ridgefield National Wildlife Refuge population.

Since this translocation, Clark County’s subpopulation grew to about 228 in 2022 and is now deemed sustainable, according to wildlife officials. These deer have even drifted off the refuge into adjacent lands, including Sauvie Island and the Shillapoo Wildlife Area.

Similar relocations of deer to other areas have resulted in an expansive range, yet not all gained as strong as a foothold as the Ridgefield subpopulation, Azerrad said.

Currently, the Washington Department of Fish and Wildlife is stringing together a contingency plan for the deer in light of persistent and future threats.

“No, it’s not an endangered species, but there’s still those lingering threats and so we’re going to be certainly continuing to address those,” he said.