Pygmy short-horned lizard COSEWIC assessment and status report: chapter 4

• Previous page
• Table of contents
• Next page

Distribution

Global range

The core range of the Pygmy Short-horned Lizard is the Great Basin Desert. The species extends from northern California and Nevada, through eastern Oregon and Washington, most of Idaho, and into the extreme south-central portion of British Columbia (Schmidt 1953, Sherbrooke 2003, Stebbins 2003). An historic record (1937) exists from extreme southwestern Montana, where the species’ current status is unknown (St. John 2002).  Figure 2 depicts their known global range.

Canadian range

In Canada, the only confirmed records of the Pygmy Short-horned Lizard are from Osoyoos in the Okanagan Valley of British Columbia, immediately north of the International Boundary. However, nearly 20 observations have been reported since these first ones were collected in Osoyoos and are discussed in more detail in the Population Abundance section. The extent of these records is the Similkameen Valley from Chopaka at the International Boundary north to Keremeos, and from the International Boundary at Osoyoos north to Kaleden (south of Penticton). These records occur throughout the South Okanogan Basin (SOB) ecosection and the southeastern part of the Okanagan Range (OKR) ecosection. It appears that these records are restricted to the very hot and dry Bunchgrass (BGxh1) and Ponderosa Pine (PPxh1) biogeoclimatic zones. Portions of the very hot and dry Interior Douglas Fir (IDFxh1) biogeoclimatic zone may be suitable as well. 

The potential range of the species in Canada has been modelled using Terrestrial Ecosystem Mapping (Iverson and Haney 2005) as a map base (Figure 3). This method identifies a substantial area where Pygmy Short-horned Lizards could occur and much of it has not been surveyed. All but one of the past observations falls within this modelled area. The Washington Gap Analysis Project (Washington Cooperative Fish and Wildlife Research Unit 1997) portrays suitable habitat within Okanogan County, consistent with usable habitat predicted by the Canadian model. 

In Okanogan County in Washington State, the Pygmy Short-horned Lizard is documented in Brewster, the town of Okanogan, throughout the Methow Valley (S. Fitkin pers. comm.) and anecdotal observations have been made as far north as Siwash Creek near Tonasket, 30 km south of the International Boundary (J. Heinlen pers. comm.).

Areas of habitat use are often represented as Element Occurrences or Areas of Occupation. This is difficult to portray for the Pygmy Short-horned Lizard as the only confirmed locations are not precise and the remaining observations are unsubstantiated. The habitat use model identifies 42,256 ha of potentially usable habitat in Canada, which constitutes less than 1% of the species’ global range.