The purpose of this study was to determine the morphological differences in the osteology and musculature of the thoracic limb of the pocket gopher and kangaroo rat. This was accomplished by first, collection of specimens, second, the preservation and preparation of bones and muscles tor study and illustration, third, sketching and photograph­ing the sketches, fourth, noting and recording origins and insertions as well as any differences in the modification of anatomy with relation to habitat requirements. These two closely related families, Geomyide and Heteromyidae, show great morphological differences. Comparative volumetric measurements show that the forelimb of the pocket gopher is approximately twice the size of the fore­limb of the kangaroo rat. Differences in the myology were found in relative length, thickness, shape, overall size, and in origin and insertion. Variations were also found in the osteology of the two forms. These differences were gen­eral outline, locations of the tuberosities for muscle attach­ment and in the length and placement of the various bone processes.

A systematic study of parasitic mites on kangaroo rats at the Nevada Test Site, Nye County, Nevada, was conducted from August, 1959, to December, 1961. The intent was to determine their kinds, numbers, seasonal occurrence, and ecological relationship with Dipodomys merriami merriami Mearns and Dipodomys microps occidentalis Hall and Dale in nuclear disturbed and contiguous undisturbed areas. Study areas were established in three major valleys -- Jackass Flats, Yucca Flat, and F renchman Flat.

Invasive species are generally regarded as detrimental to native communities because they cause increased competition and community structure alterations. There is therefore a critical need to understand the ecological processes underlying the establishment and spread of invasive species. While most studies to date have focused on the role of competition in species invasions, trophic dynamics may also play a fundamental role in the establishment and spread of non-natives, especially in cases when a non-native species experiences differential predation pressure relative to a native competitor. Herein I explore the potential for differential granivory pressure by a native rodent (Heermann’s kangaroo rat, Dipodomys heermanni arenae) on native shrubs and an invasive plant (Veldt grass, Ehrharta calycina). Veldt grass, a perennial tufted grass native to South Africa and introduced to California in 1929, is highly invasive, and the shift of native coastal dune scrub to a grassland, dominated by Veldt grass, is considered one of the factors that led to the decline of the federally endangered Morro Bay kangaroo rat. However, kangaroo rats are largely graminivores (consume grass seed) and are known to consume invasive grasses and other plants. Differential seed preferences for native and Veldt seed were examined by placing feeding stations containing each seed type in habitats dominated by either native plants or Veldt grass. Each feeding station was monitored using motion-activated game cameras and the amount of each seed type collected by nineteen individually-marked, wild kangaroo rats was documented. These marked kangaroo rats were monitored both in native and Veldt grass habitats, allowing for the testing of habitat origin (Native vs. Veldt), sex (male or female) and seed type on the amount of seed taken. Nine of the kangaroo rats harvested Veldt grass seed. Though females collected more seed than males, there was no difference between the amounts (% of available seed) of Veldt grass and native seed collected. Habitat of origin (i.e., habitats with Veldt grass present or habitats without Veldt grass) had no effect on the amount of seed collected or the type of seed collected. During seed station trials, kangaroo rats were also recorded removing seed heads from naturally occurring Veldt grass stalks, providing clear documentation that Heermann’s kangaroo rats do collect Veldt grass seed. Accompanying laboratory seed preference trials were also conducted to confirm the consumption of Veldt grass seed. These controlled laboratory trials revealed that Heermann’s kangaroo rats will consume Veldt grass seed, although Veldt grass seed was consumed in smaller amounts (g) than millet and sunflower seed, which were presented simultaneously. These findings indicate that non-native Veldt grass may provide an additional or alternative source of seed for kangaroo rats, which could provide a partial explanation for why kangaroo rats are able to survive in monocultures of Veldt grass.

The purpose of this study was to compare the morphology of the hind limb of the pocket gopher with that of the kangaroo rat and to determine their differences. This was accomplished by first, obtaining the specimens; second, preparation of the specimens for preservation and dissection; third, photographing and tracing the muscles; fourth, noting the origin and insertion of each muscle and their general morphology; and fifth, preparation and photographing of the bones. Comparative volumetric measurements were made of the muscles of the two animals to determine the differences between them. These two families, Geomyidae and Heteromyidae, are closely related but show great morphological differences which are adaptive due to their different environments and habits. The volumetric measurements of the two animals showed the shank of the kangaroo rat to be twice the size of that of the pocket gopher. The muscles used by the kangaroo rat in jumping are longer and larger as indicated by the volumetric displacement and linear measurements. Also, linear measurements were made of the various muscles and bones, These measurements also showed the variation in lenth and width, with those muscles of the kangaroo rat baing longer and wider. In the study of the bones, the general outlines of the two forms were vastly different. The location of tuberosities, size of the tuberosities for muscle attachment, bone length and width made up these differences. Origins, insertion, actions and description of the muscles are given for each animal.

Activity curves for Dipodomys ordii were developed from data obtained from a study utilizing an electrically monitored trapping grid. The curves for non-perturbated populations showed an initial post-dusk peak, followed by increasing activity and a large pre-dawn peak; but after ten dominant animals had been removed, the largest activity peak was post-dusk. Differences in activity patterns were not found among sex, age or reproductive classes. Rising ambient temperatures, falling barometric pressures, winds over 3.2 km/hr and the absence of the moon depressed capture numbers; while increasing humidity (relative and absolute), decreasing soil temperatures at 20 and 40 cm below ground level, rising barometric pressures, winds under 3.2 km/hr and clear periods with moonlight increased capture numbers; but only cloudy periods significantly altered the shape of the curves. Low statistical correlation indicated that other independent environmental variables, in addition to those considered, determined the observed activity patterns. Visual observations did not differ significantly from trap results.

Geographic Information Systems (GIS) and remote sensing technologies were used to identify and describe potential habitat for three species endemic to the Southwestern United States; the Golden-cheeked Warbler (Dendroica chrysoparia), the Black-capped Vireo (Vireo atricapillus), and the Texas kangaroo rat (Dipodomys elator). For each species, the computerized classification of digital satellite imagery was integrated with ancillary spatial information (e.g. soils, geology, and land use) to construct a data base to be used for ecological evaluation as well as habitat protection and management measures.