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In northern Colorado, thirteen-lined ground squirrels (Spermophilus tridecemlineatus) are less numerous in colonies of black-tailed prairie dogs (Cynomys ludovicianus) than in surrounding grassland areas, but the ecological factors responsible for this difference are unknown. In 2005, squirrels were trapped on and adjacent to a 70-ha colony to compare relative abundance and demographic variables in and out of colonies. Although some aspects of the population ecology of squirrels were similar, differences in demographic variables and abundance suggested that colonies may be poorer quality habitat. It has been argued that sociality influences the degree of male-bias in juvenile dispersal in North American ground squirrels. Thirteen-lined ground squirrels are relatively asocial, but no estimates of juvenile dispersal are available to assess whether dispersal is less male-biased than for other squirrels. This study determined environmental factors likely influence both sociality and sex-biased dispersal in Spermophilus.

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Abby Benson studied ecology at the University of Colorado and completed her Master´s degree at California State University, Fullerton. She currently works for the United States Geological Survey and enjoys hiking.

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