Washington State Periodic Status Review for the Columbian White-tailed Deer (2016)

Columbian White-tailed Deer (Odocoileus virginianus leucurus) is the westernmost subspecies of whitetailed deer. Although widespread and numerous across much of its North American range, this subspecies occurs in relatively low numbers in a highly restricted range. Once Columbian White-tailed Deer (CWTD) ranged widely across much of western Washington and Oregon, however; habitat loss and degradation as well as overhunting led to a significant range contraction and decline in their numbers. This led the U.S. Fish and Wildlife Service (Service) to include the Columbian White-tailed Deer as an Endangered Species immediately upon adoption of the Endangered Species Act (ESA) in 1973. The Washington Department of Game designated it as a State Endangered Species in 1980.

Columbian White-tailed Deer currently occupy two isolated populations, the larger of which occurs in Douglas County, Oregon. The other occurs along the shores of the lower Columbia River with a range extending from Ridgefield National Wildlife Refuge (NWR) downstream to the Lewis and Clark NWR. This population is smaller than the Douglas County population (> 6,000 deer versus < 1,000 deer) and is the only ESA-protected population.

Since it was first listed as a State Endangered Species in Washington, the Columbia River population of CWTD has fluctuated. Since then surveys conducted by the U.S. Fish and Wildlife Service estimated a low point for this population in 2002 when they estimated only 545 deer. Their estimated population since then has generally been lower than estimates for the years immediately after Washington State designated it as an Endangered Species. Population numbers have increased in recent years according to the U.S. Fish and Wildlife Service, with the estimated deer population reaching a high of 966 deer in 2015.

Partners have carried out a number of activities to help bolster this population, including habitat protection and restoration, predator control, and translocating deer to enhance their numbers and expand their geographic range. These activities have had mixed results. On the positive side, the predator control program seems to have measurably benefitted fawn survival and recruitment. Deer translocated to Tenasillahe Island have also responded positively to their new environment. With the exception of the recent translocations to Ridgefield National Wildlife Refuge, where it is premature to draw major conclusions, all other translocations have shown mixed results up until now.

These management challenges have led to recent populations estimates that resemble population estimates from most of the 1980s. One generally accepted theory as to why the population has shown a mixed response to management is that there is an overall lack of suitable habitat within the occupied lower Columbia River range. This likely has inhibited the population's ability to expand beyond a limited carrying capacity.

Although deer numbers seem stifled by habitat constraints, recent proposals likely will shed light on potential ways to enhance the population. One such proposal is for a Population Habitat Viability Assessment that WDFW plans to carry out this year. This will provide a description of the habitat needs and deer numbers required for a viable population and likely will help WDFW and the Service examine the appropriateness of current recovery goals. Another is a proposal by the Washington Department of Transportation to analyze habitat connectivity for this population of CWTD. The results of this will identify habitat linkages that may subsequently be conserved and managed to help expand the population beyond its limited range.

Because of the low population, fragmented and low quality habitat, along with the uncertainty as to what constitutes a viable population, the Washington Department of Fish and Wildlife recommends retaining CWTD as a State Endangered Species in Washington.