THE DISTRIBUTION OF THE CASCADE MANTLED GROUND-SQUIRREL, SPERMOPHILUS-SATURATUS, IN BRITISH-COLUMBIA

The Cascade Mantled Ground Squirrel, Spermophilus saturatus, only occu rs in southwestern British Columbia (Canada) and Washington State (Uni ted States). Little was known about the squirrel in British Columbia p rior to this survey. Range and distribution were determined from museu m records, survey forms, opportunistic observations, visual counts, an d live-trapping. Visual counts were used most often and were more effe ctive at locations where the relative abundance of S. saturatus was hi gh. S. saturatus was found further north and west than previously repo rted, but not as far east as indicated by museum records. S. saturatus was uncommon and had a discontiguous distribution in British Columbia , which could be a result of frequent extinctions and slow recolonizat ions at the northern portion of their range. Marginal climatic conditi ons, drainage systems that delineate the range of S. saturatus, and di splacement by the Columbian Ground Squirrel (S. columbianus) at the ea stern extent of S. saturatus range in British Columbia, are all probab le factors limiting the distribution of S. saturatus. Although the squ irrel's distribution is limited, the population is not likely in dange r of extinction at present. Trapping at four locations indicated good overwintering success of the most vulnerable age group, young born the previous year.