Distribution of the Eastern Short-Horned Lizard (Phrynosoma douglassii brevirostre) in Alberta, Canada

Abstract

The eastern short-horned lizard, Phrynosoma douglassii brevirostres reach- es the northern limit of its geographical range in southeastern Alberta. Populations in this area are found in the drainage basins of the South Saskatchewan River, Pakowki Lake and Milk River. The vegetation of the area is typical short-grass prairie. Popu- lations are confined to south-facing slopes, badland-grassland ecotones and Bearpaw shale outcrops. The range is within the dry steppe climatic region, having short, hot summers and high insolation. The active season of the lizards is from late April-early May until early September. Geologic and vegetative factors appear to account for the presence of P. d. brevirostre at high latitudes. This report constitutes a summary of the known distribution of the eastern short- horned lizard (Phrynosoma douglassii brevirostre) in Alberta, and a description of the phys- ical and biotic characteristics of the range. Although P. d. brevirostre occurs in Saskatch- ewan (Cook 1970, 1984, pers. comm.; Chandler 1965; Logier and Toner 1961), its range in that province is poorly documented. Its range in Alberta is better established, and seems to be more extensive. Because very few lizard species are found in Canada, an examination of the range of P. d. brevirostre in Alberta may provide information on the environmental tolerances of boreal lizards. As such, this account is complementary to that of Guyer and Linder (1985), who documented aspects of the ecology of P. d. douglassii in southeastern Idaho. Phrynosoma douglassii brevirostre has the most easterly distribution of the P. douglassiz complex, and ranges the furthest north of all iguanid lizards. Its documented range is confined mainly to the United States, where it extends north from northwestern Kansas to Montana, as far east as western Nebraska and western South Dakota, and as far west as northeastern Utah (Reeve 1952; Schmidt 1953). Schmidt (1953) and Smith (1946) both reported that the range of P. d. brevirostre presumably extends into southern Alberta and Saskatchewan, without citing any particular localities in these Provinces. Reeve (1952) did not list any Canadian localities for this subspecies, although he did note one specimen taken on the Milk River at 49°N, and the distribution of P. d. brevirostre on his range map does extend slightly into Alberta. Conant (1978), Behler and King (1979) and Stebbins (1985) noted that the range of P. d. brevirostre extends into extreme southeastern Alberta and southwestern Saskatchewan, but the northern limits they reported are not totally congruent. No previous account of the subspecies' range in Alberta is complete. The range map shown in Fig. 1 is a compilation of all known records. These records are summarized in Table 1 and the numbers given after each record correspond to those presented in Fig. 1.