Date of Award:

5-1978

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Wildland Resources

Department name when degree awarded

Wildlife Science

Committee Chair(s)

David F. Balph

Committee

David F. Balph

Abstract

This research describes and analyzes the behavior of free-living Uinta ground squirrels (Spermophilus armatus) temporally, spatially and with reference to differences in sex, age, population density and habitat. In addition, the relationships between local meteorological parameters and time spent above ground are described and analyzed.

The frequency of eight behaviors, feeding, moving, encounters, upright, motionless, grooming, nest gathering and calling, among ground squirrels was found to be labile, varying in frequency with time of day, period of the season, sex, age, population density and habitat, and varying in spatial distribution within the home range.

The dominant behavior, feeding, was most frequent during the first and last two hours of the day and tended to occur within the home range core during these hours. During the midday periods home range use became more general and the frequency of the other behaviors increased as feeding frequency decreased.

During periods of sexual activity (the beginning and end of the homeothermic season), male ground squirrels displayed high frequencies of encounters, moving and calling behaviors. During the midperiod of the season males increased the frequencies of feeding, grooming and nest gathering. The lactation period was the period in which most behaviors peaked in frequency among females. The frequencies of moving, upright, nest gathering and calling all had seasonal peaks during lactation. Between sexes, males tended to exhibit higher frequencies of behaviors that contributed to social interaction than did females, and females tended to exhibit higher frequencies of behaviors that contributed to self-maintenance and productivity than did males. Few consistent differences in frequency of behavior were observed between age groups of the same sex.

Home range size varied seasonally and with sex of the squirrel. Home ranges of males were large during periods of sexual activity and small during the postbreeding period. Home ranges of females tended to increase in size as the season progressed. Among all squirrels,moving tended to be peripherally distributed within the
home range. Because of the large amount of individual variation in the spatial distribution of specific behaviors within the home ranges of groups of like squirrels it was concluded the distribution of behavior within the home range of an individual was likely to be a result of the unique distributions of physical and social characteristics of its home range.

Frequency of behavior and spatial distribution of behaviors within the home range were also related to population density among ground squirrels. During years of high population density females exhibited higher frequencies of behaviors that could be related to aggression than they did during years of low population density. These differences in behavior frequency among females are consistent with the greater intolerance of conspecifics by females than by males, hence their greater sensitivity to high population numbers. Among all squirrels the distribution of specific behaviors tended to become less proportional to the distribution of home range use as effective density about the home range increased.

Distribution of behavior within the home range and distribution of use within the home range were correlated with the spatial distribution of encounters initiated by neighbors upon a home range resident and the distribution of encounter losses within its home
range. Maintenance of a given home range appears to be related to the frequency of encounters won within the core area.

Time spent above ground by squirrels was correlated with the seasonal variation in ambient temperature and heat exchange between the individual and its environment. During the first 40 days of the 1970 season activity tended to increase as ambient temperature or heat gain increased. Thereafter activity was negatively correlated with ambient temperature and rate of heat gain. The principal mode of thermoregulation appeared to be behavioral, i.e., avoiding heat and water stress by use of alternative microhabitats, principally the burrow, as sinks for the dissipation of heat. It is believed that the seasonal variation meteorological factors with the attendant changes in quantity and quality of foods to be the prime factors influencing the length of the homeothermic season.

The strategies squirrels use to increase individual fitness and the implications of this research with regard to estimating population density, predicting effects of habitat manipulation and management of squirrels at rehabilitation sites are discussed.

Checksum

1eb0c83c17834a2ffde552b124a87077

Download

Share

COinS

Copyright for this work is retained by the student. If you have any questions regarding the inclusion of this work in the Digital Commons, please email us at .