A preliminary study of Richardson's ground squirrels (Spermophilus richardsonii) was conducted in the Quinn River Valley, north of Winnemucca Nevada, between 8 June and 21 July 1977. Population densities of juveniles were nearly equal in cheatgrass, northern desert shrub, and crested wheatgrass habitat types (20.3/ha in cheatgrass, 32.2/ha in northern desert shrub, and 27.9/ha in crested wheatgrass). Sex ratios among juveniles strongly favored females, in contrast with some previous studies in which 1:1 , sex ratios existed for juveniles. Squirrels in the northern desert shrub habitat lost weight over a four-week period in mid-summer, suggesting that overwinter mortality might be very high in this habitat. Squirrels in the crested wheatgrass habitat maintained stable weights over a similar period of time. Preliminary results of this study, as well as data from other studies of ground squirrels throughout western North America, suggest that these animals have high reproductive potential and dispersal ability. These factors must be considered if management of ground squirrel populations is to be effective.
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