The genetic structure of 26 natural populations of three species (S. tridecemlineatus, S. mexicanus, and S. spilosoma) of the Ictidomys subgenus of ground squirrels was analyzed using chromosomal and electrophoretic techniques. Chromosomal variation was not observed in S. mexicanus, and only slight karyotypic variation was found in the other two species. Chromosomal evidence indicated hybridization between S. tridecemlineatus and S. mexicanus, placing these species within the classical definition of semispecies. Analysis of electrophoretic variation at 29 genetic loci indicated close genetic relationships between these species. Evolution in Ictidomys appears to be linked with Pleistocene events, and speciation appears to have occurred within the last 155,000 years.

I studied round-tailed ground squirrels (Spermophilus tereticaudus) to determine if presence of water or green vegetation significantly increased reproductive success. I compared the number of juveniles produced, body weights, and diets of squirrels during 1981-84 on 2 plots with green vegetation and no free water, on 3 plots with free water and no green vegetation, and 2 control plots. Reproductive success and body weights of adult and juvenile squirrels were significantly higher (P ≥ 0.001) on plots with green vegetation than on either watered or control plots. Body weights of squirrels on plots with water only and control plots were not significantly different (P ≥ 0.05). Adult squirrels without access to green vegetation during winter and spring failed to reproduce even though free water was readily available. Percent of diet overlap, diversity, and evenness of squirrel diets on control and watered plots were not significantly different. Green vegetation appeared to be the limiting factor for round-tailed ground squirrels.

In an attempt to describe, explain, and show the demographic significance of annual variations in the nesting distribution of Uinta ground squirrels, a study was conducted during the summers of 1964 through 1967 in northern Utah. Procedures included both trapping and direct observation. It was found that females tended to nest in open, previously inhabited, grassy areas. Males resided throughout a variety of habitats. This typical nesting distribution was established initially in the summer by juveniles shortly after they first appeared aboveground. The extent to which the distribution was maintained the following spring depended largely upon the number of female s which emerged from hibernation and the pattern in which they emerged. The number of females which appeared depended upon the previous year's breeding density and productivity. The pattern of emergence appeared to be a function of an inherent pattern of physiological arousal from hibernation and the prevailing weather conditions. The number and sequence of emergence of females in the early spring affected breeding and social organization in a manner which limited the number of females which retained residences in the study area. This determined the actual breeding density. In addition, emergence influenced the production of offspring by altering both the breeding density and the number of non-productive females in the population. The adaptive significance of the system and its applicability to other species are discussed.

The annual demography of a population of antelope ground squirrels in Curlew Valley, Utah was studied by measuring population density, natality, and mortality. Capture- recapture techniques yielded lower estimates than the Hayne strip- census. The estimates suggested 1968 was a year of population decline. One hundred seventy- three squirrels were collected and autopsied to obtain sex ratio , age structure, natality, and mortality data . The seasonal sex ratios for adult and yearling squirrels showed 82 percent females in spring 1968, this gradually changed to 56 percent by winter . The seasonal sex ratios of the young squirrels showed 59 percent females upon emergence from natal burrows in summer 1968, increasing to 79 percent by winter. The squirrels collected were aged by cementum annuli . The oldest were believed to be 5 years old . They composed 1.2 percent of the collection while young- of- the-year composed 38. 7 percent. The estimate of mean corpora lutea was 7.6, the mean embryo count was 7.2, and the mean post-partum placental scar count was 5.8. The mean corpora lutea count for yearlings was statistically lower than the count for adults and the mean ovulation rate for 1968 statistically lower than the rate for 1969. An estimate of litter size from four nests gave a mean of 4.5. In 1968, the conception rate was 91 percent with yearlings comprising 75 percent of those not conceiving. In 1969, the rate was 100 percent. Pre-Emergence mortality of the young was 41 percent. post-emergence mortality was 86 percent, and mortality, March - November, 1968 was 92 percent. Adult and yearling spring-to-spring mortality for study area squirrels calculated from retrap data was 81 percent. Spring-to-spring mortality calulated from age distribution data and Ricker's formula was 71 percent. The spring-to-fall mortality for 1968 calculated from density estimates and age distribution data was 53 percent.

Thesis (Ph. D.)--Carleton University, 2002. / Includes bibliographical references (p. 166-178). Also available in electronic format on the Internet.

Thesis (M. Sc.)--Carleton University, 2004. / Includes bibliographical references (p. 119-132). Also available in electronic format on the Internet.

Thesis (M.Sc.) - Carleton University, 2005. / Includes bibliographical references (p. 134-145). Also available in electronic format on the Internet.

Thesis (Ph.D.) - Carleton University, 2006. / Includes bibliographical references (p. 118-138). Also available in electronic format on the Internet.

Hematological comparisons were made on the Uinta ground squirrel (Citellus armatus) trapped at different altitudes and during vari ou s stages of seasonal activity in 1965 and 1966. Hematological variation due to sex, sexual activity and body weight were also analyzed. Ground squirrels were secured from the Mt. Timpanogos area near Provo, Utah County, Utah. Erythrocyte count, hematocrit, total blood hemoglobin, mean erythrocyte volume, mean erythrocyte hemoglobin and reticulocyte counts were measured using standard procedures; banding patterns of hemoglobin and serum proteins wer e determined by means of electrophoresis with polyacetate strips.

The purpose of this investigation was to study the weight changes of selected internal organs to determine possible physiological variation occurring at six different altitudes ranging from 5,800 to 8,500 feetand during the summer season. This report was limited to the study of changes in the adrenal glands, kidneys, testes, heart and intestines. Electrocardiogram, heart and respiration rates were investigated also. These changes were statistically analyzed to determine possible seasonal differences along with any significant changes occurring at different elevations. The results of the study should in part overcome the lack of current experimental data for Citellus armatus.