Habitat

Columbian white-tailed deer are the western-most subspecies of white-tailed deer, and historically live in a geographic range that extends from southwestern Washington and much of western Oregon (Smith, 1987). However, anthropogenic habitat changes have significantly altered population distributions of this subspecies in the northwest, and what was once a continuous distribution throughout the geographic range mentioned above has resulted in two isolated populations: Douglas County, Oregon and along the lower Columbia River (Washington Department of Fish and Wildlife, 2012). Columbian white-tailed deer have been listed as an endangered species at the federal level since 1967 and at the state level since 1980 (Washington Department of Fish and Wildlife, 2012). Columbian white-tailed deer are a riparian species (Smith, 1987), meaning that their habitat typically exists in the area comprising the interface between land and a river or stream. As a result, alterations to habitats in these areas are the most influential.

Figure 2 - Historic distribution of Columbian white-tailed deer populations (Suring, Vohs, 1979). Red arrows help highlight approximate population locations.

Substantial research has been conducted on the specific characteristics of the habitats this subspecies most commonly inhabit. Researchers at Oregon State University (OSU) found a strong preference for habitats containing a higher species diversity of plant coverage, and a significantly lower preference for habitats containing lower species diversity (Suring, Vohs, 1979). The major plant types that existed in these areas were species of grasses, shrubs, horsetails, and large trees (categorized as “forests”). A higher level of species diversity among these plant categories provides both coverage and foraging facilitation for deer populations (Suring, Vohs, 1979).

Figure 3 - Distribution of Columbian white-tailed deer populations along the Washington/Oregon border
http://wdfw.wa.gov/about/regions/region5/wildlife_reports/2011/graphics/jun20_2011c.jpg

In another study conducted by researchers at OSU, a strong correlation was observed between high survival in lesser-developed regions, and lower survival in more highly developed regions (Ricca, Anthony, Jackson, Wolfe, 2002). Specifically, annual survival of deer in lesser-developed regions was 0.77, compared to only 0.66 in highly developed regions (Ricca, Anthony, Jackson, Wolfe, 2002). The researchers also noticed poor levels of health in the expired deer they examined, which indicates that the deaths could be related to deficient living conditions rather than natural predation or other causes.

Figure 4 - Relationship between the level of land development and the percent coverage of forest, shrubs, thistle, and grass (left) (Burton, Samuelson 2008). Relationship between habitat plant composition and level of use (habitat use index) by Columbian white-tailed deer (right) (Suring, Vohs, 1979). Novel figure

Figure 4 (above) compiles data obtained from two separate studies (Burton, Samuelson 2008) and (Suring, Vohs 1979) (see references page for more details). The graph to the left shows the relationship between the level of land development and the percent coverage of plants critical to natural Columbian white-tailed deer habitats (Forest coverage, shrubs, thistle, and grasses). A negative correlation is observed between the level of development and the percent coverage of important plants. The graph to the right shows the relationship between plant composition and level of use (defined as habitat use index) by Columbian white-tailed deer. Columbian white-tailed deer most highly utilize habitats containing high amounts of forest, shrubs, thistle, and grass. These graphs demonstrate how habitats containing the characteristics mentioned above are vital to Columbian white-tailed deer, and how urbanization and development leads to the decline of these specific habitats. 

This information illustrates exactly how important preservation of natural habitat is for the survival of Columbian white-tailed deer, and suggests that one of the critical factors contributing to the decline of this subspecies appears to be habitat alteration and destruction. It is important to note that further research should be conducted on the survival and life patterns of deer in more urban areas, as relatively little research has been done on this subject (Grund, McAninch, Wiggers, 2002).

Learn more about habitat preservation here.

Continue reading about Columbian white-tailed deer and hunting here.