Published: January 2023
Author(s): Jeffrey M. Azerrad
The Columbian white-tailed deer (Odocoileus virginianus leucurus) is a subspecies of white-tailed deer. Habitat loss and degradation as well as overhunting caused the species’ range to significantly contract and their population numbers to decline. The subspecies exists in two isolated populations. The larger population occurs entirely in southwest Oregon, while the other is in southwest Washington and northwest Oregon along the lower Columbia River. The lower Columbia River deer population is the smaller of the two populations. Until recently this population was federally listed as Endangered by the U.S. Fish and Wildlife Service (reclassified to Threatened in 2016) and is currently a State Endangered species in Washington.
Columbian white-tailed deer were listed at the federal level in 1970 and 1973, and by the State of Washington in 1980. Since 1980, the size of the lower Columbia River Columbian white-tailed deer population has fluctuated. Surveys conducted by U.S. Fish and Wildlife Service estimated a low of only 545 deer in 2002. The population has now rebounded, with an estimated population of 1,296 deer in 2022.
Partners have helped this population increase through habitat protection and restoration, predator control, and translocations. These activities have increased productivity in occupied habitat and have expanded the range of the lower Columbia River population. Translocations, particularly to Tenasillahe Island and more recently to Ridgefield National Wildlife Refuge, have also been greatly successful in creating new breeding subpopulations, although other translocations have been less successful.
A recent Columbian white-tailed deer population and habitat viability assessment (PHVA) shed light on this population’s demography. The assessment concluded that the large, secure subpopulations around Ridgefield National Wildlife Refuge and Julia Butler Hansen Refuge for the Columbian white-tailed deer are the most resilient of all subpopulations along the lower Columbia River. The assessment also showed a high potential for population growth around Ridgefield as well as a low overall risk of extinction in the next 50 years.
Compared to the other subpopulations, the viability assessment revealed low population growth potential and a greater risk of population decline in the centrally located subpopulations downriver of Longview, Washington. These subpopulations were also identified as a bottleneck to deer movement between the larger upriver and downriver subpopulations.
In our last periodic status review, we expressed concerns about the vulnerability of occupied habitat to threats such as climate change, emerging diseases, and a lack of secure and functionally connected habitat. At that time, we were also uncertain about the viability of a newly established subpopulation at Ridgefield National Wildlife Refuge. Although the threats have not abated since then, we are no longer uncertain about the viability of the Ridgefield subpopulation given the encouraging projections of the viability assessment for this subpopulation. We are now much more confident that the deer at Ridgefield have established a viable subpopulation with significant growth potential.
The new information from the PHVA also sheds light that is relevant to this status assessment. The PHVA revealed a low overall risk of extinction rangewide as well as for each of the individual lower Columbia River subpopulations. We consequently conclude that Columbian white-tailed deer does not adhere to the definition of State Endangered, which requires that the species be “seriously threatened with extinction” (WAC 220-610-110). The Washington Department of Fish and Wildlife thus recommends reclassifying the Columbian white-tailed deer to Threatened.
Azerrad, J. M. 2023. Periodic status review for the Columbian White-Tailed Deer. Washington Depart-ment of Fish and Wildlife, Olympia, Washington. 31 + iv pp.
Draft documents are provided for informational purposes only. Drafts may contain factual inaccuracies and may not reflect current WDFW policy.