Causes of the unequal sex ratio in populations of adult Richardson's ground squirrels
- 1 October 1979
- journal article
- research article
- Published by Canadian Science Publishing in Canadian Journal of Zoology
- Vol. 57 (10), 1849-1855
- https://doi.org/10.1139/z79-245
Abstract
Four hypotheses, postulated to explain the unequal sex ratio characteristic of populations of adult Richardson's ground squirrels (Spermophilus richardsonii), were examined in a population of this species near Hanna, Alberta.One hypothesis, postulating a disproportionate loss of adult males in early spring, was supported by our observations. Males emerged earlier and were lost from study plots in greater numbers than females; they moved more widely, which probably increased their vulnerability to predation. A second hypothesis, postulating a disproportionate loss of juvenile males during their first summer, was also supported by our data. Loss of males exceeded that of females. Juvenile males moved farther and in greater numbers than females, which seemed to make them more vulnerable to predation; significantly more juvenile males than females were among the prey of buteos feeding young. That mortality through predation falls disproportionately on males, a third hypothesis, was therefore also supported. However, our data on loss from midsummer to the following spring do not support the hypothesis that differential mortality occurs over winter.This publication has 3 references indexed in Scilit:
- Effect of climatic conditions on the annual activity and hibernation cycle of Richardson's ground squirrels and Columbian ground squirrelsCanadian Journal of Zoology, 1977
- Population Structure and Dispersal in Richardson's Ground SquirrelsEcology, 1977
- An Experimental Comparison of Screech Owl Predation on Resident and Transient White-Footed Mice (Peromyscus leucopus)Journal of Mammalogy, 1967