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This study was initiated to investigate the distribution patterns of two species of pocket gophers, Thomomys umbrinus albicaudatus Hall and T. talpoides wasatchensis Durrant whose ranges come together in the Hobble Creek area, Utah. The effect of certain ecological factors upon their distribution was determined. The ecological factors included: vegetation and land use, soil, moisture and exposure, hybridization and interspecific competition. From morphological examination no interbreeding was detected even though the breeding seasons of the two species correspond. A limited area was found where the ranges of the two species are in contact. A lack of available moisture was determined to be a major factor inhibiting the distribution or talpoides in non-irrigated soils. Umbrinus is very versatile toward moisture and does not appear to be affected. Both species show a preference for sandy or gravelly-loam soils. Interspecific competition apparently inhibits the distribution of both species where the ranges come together. It is supposed that where only one species occurs that ranges will continue to be extended with talpoides being limited to the more moist areas. The other ecological factors are of no apparent significance to the distribution of either species except as they relate to the amount of available moisture.

Golden-mantled ground squirrels (Citellus lateralis Say) typically inhabit coniferous forest regions, but they occasionally occur in desert shrub habitats. The principal purpose of this study was to observe activities of mantled squirrels in a sagebrush community, and to ascertain factors which contribute to their success in an unusually arid habitat. Squirrels of this community belong to the subspecies C. l. lateralis; however, intergradation between typical C. l. lateralis and C. l. castanurus is evident. This community is in the Wasatch Mountains at an elevation of 5,750 feet, and in the Upper Sonoran Zone. These three conditions were not previously recorded for members of this subspecies.

The objective of this research is to assess the effects of various quantities of supplemental food (seed) on population estimates and mortality rates of desert rodents . The supplemental food is meant to stimulate natural vegetational productivity. If food availability significantly affects the population parameters methods of population estimators previously used may be in error. Hopefully this study will aid small mannnal research by designating whether, in part, population estimates and mortality rates are in error because of high vegetational productivity. The hypothesis of this study is that supplemental food in the natural environment decreases population estimates and mortality rates of desert rodents.

Three heteromyid rodent species were studied in relation to a large dry wash in Millard County, Utah, during the summer, 1974. Data were gathered with three trapping grids and analyzed to determine if the dry wash influenced rodent movement and distribution patterns. Dipodomys ordii and Dipodomys microps were distributed non-randomly in the dry wash and adjacent habitat, but Perognathus Zongimembris seemed to be randomly distributed. Dipodomys ordii was significantly correlated with wash habitat, but D. microps was found most frequently in upland areas. Soil and vegetative differences and competition were possible causes for the observed distribution. The wash was observed as a source of dispersing young D. ordii. It was concluded that the dry wash had little effect on daily movement of the rodents observed.

The role of social play in juvenile behavioral development was examined in the punare (<u>Thrichomys apereoides</u>). Three proposed functions of social play were evaluated: 1. play serves to develop agonistic skills, 2. play has a role in the onset of weaning and 3. play establishes dominance relationships among participants. Eight litters consisting of three juveniles and both parents were observed from birth until eight weeks of age, and the content, sequence and duration of parental and play behaviors were recorded. Adult agonism was characterized in paired encounters between. unfamiliar adults. Encounters between unfamiliar juvenile dyads were conducted and compared to litter mate play. Sex specific differences in social play were concordant with observed differences in adult agonistic interactions. Play bouts between male juveniles were more frequent, of greater duration and incorporated more dominance reinforcement behaviors than bouts between females. Mothers tended to avoid playing with offspring, while paternal play was frequent. Self-handicapping was observed during father-daughter play. Dominance relationships were evident during play, with strong, stable hierarchies established among male juveniles. Adult males dominated all offspring and juvenile males dominated female littermates. Unfamiliar juvenile play bouts were shorter in duration and more frequently resulted in avoidance than bouts among litter mates. These results suggest that punare social play functions to develop agonistic skills while concurrently establishing dominance relationships. The early establishment of dominance relationships may serve as a non-injurous means of precipitating male-biased post-weaning dispersal. / Master of Science

Changes in locomotor rhythms of Mus musculus as a response to combinations of lighting and feeding cues were quantitatively assessed in this study. Time allowed for feeding was varied (3, 5, and 7 hours) to examine effect of different zeitgeber strengths on locomotor pattens. The effect of temporal light/dark cue removal on locomotor rhythms was examined in conjunction with restricted feeding regimes. The potential to use blood glucose levels as a temporal feeding cue was examined by comparing the locomotor rhythms of mice consuming either a high glucose or high starch diet. Blood glucose curves for animals under restricted feeding regimes of 1 and 5 hour lengths were determined for the two diets. Most of the locomotor activity records from animals in total darkness and a restricted feeding regime contained rhythm splitting. Only the anticipatory component of locomotor activity was synchronized by the 7 hour and 5 hour restricted feeding regimes in total darkness. Mice on a 3 hour restriction regime also exhibited a free run component in locomotor activity. The two experimental diets did not produce statistical differences in plasma glucose concentrations when animals were placed on a 5 hour restricted feeding regime in total darkness, but did when they were placed in a light/dark l2:l2 lighting cycle with a 1 hour feeding regime. The locomotor records indicated that free-running locomotor components were synchronized only by light/dark transitions, while the anticipatory component was synchronized by food presentation. The results of this study are consistent with a Two-Oscillator Model for control of activity rhythms. / Master of Science

In the southwestern United States there is a delicate balance between the existing grasslands and the rodent fauna. The purpose of this investigation was to determine the influence of secondary succession of native grasslands upon the ecology and distribution of small rodents. Two methods of determining the rodent species were plot quadrates and trap lines using Sherman live traps.

The aim of this study was to investigate the possible toxicity of the flavonoid-containing plant, Artemisia afra and especially establish the safety of the aqueous extract of this plant after acute and chronic administration to mice and rats respectively.

The primary aim of this study was to investigate the role of food supply and ground cover on the community structure, population dynamics and demography of terrestrial small mammals in a subtropical grassland. This aim was achieved through a series of food supplementation and cover manipulation experiments conducted at eKundizeni Farm near Matsapha, Swaziland, over a 28 month period. The effects of five different diets on the rodent Mastomys natalensis were investigated in the laboratory, and the results showed that rolled oats and rabbit pellets were suitable for growth and reproduction in this species. The effects of supplementary food were investigated on two supplemented grids and one control over a twelve month period. Small mammal biomass increased significantly on the supplemented grids in relation to the control. This increase in biomass was the result of a twofold increase in the numbers of M natalensis. Food supplementation further affected M. natalensis by: extending the breeding season of females; increasing body weight; increasing survival; and decreasing home range area. Food supplementation had a weak positive effect on the density of another rodent Lemniscomys rosalia, but did not affect any other demographic feature of this species. Food supplementation did not have a demographic effect on any other species of small mammal captured. The effects of vegetative cover were investigated, over a twelve month period, on two control grids and four manipulated grids on which the vegetative cover was mechanically reduced. Supplementary food was added to two of the latter four manipulated grids. The biomass of small mammals, including M. natalensis, was lower on grids with reduced vegetative cover than on the controls. However, food supplementation resulted in a significant increase in the biomass of M. natalensis on one of the manipulated grids. Hence, M. natalensis was induced to shift to a habitat with reduced cover by the provision of supplementary food. Additional information on the population dynamics, age structure, reproduction and diet of M natalensis, L. rosalia, Mus minutoides and Steatomys pratensis is also presented. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1997.