Jerry R. Choate

Identification and Recent Distribution of White-Footed Mice (Peromyscus) in New England

External features and quantitative cranial characteristics can be used to distinguish between Peromyscus leucopus and P. maniculatus where they occur sympatrically in New England. Discriminant function analysis was used to prepare a test by which skulls of adults of these species can be identified. Geographic and ecological distributions of white-footed mice in New England were reviewed.

Karyotypic Relationships within the Short-Tailed Shrews, Genus Blarina

Short-tailed shrews of the genus Blarina exhibit considerable geographic variation in both diploid number and fundamental number. Four chromosomal groups are recognized within the genus: Blarina brevicauda , FN = 48; 2N = 50, 49, or 48; B. carolinensis , FN = 45 or 44; 2N = 46, 39, 38, or 37; B. c. peninsulae , FN = 52; 2N = 52, 51, or 50; B. hylophaga , FN = 62, 61, or 60; 2N = 52. B. c. peninsulae also may be a distinct species, but exact determination must await location and analysis of a zone of contact with B. carolinensis .

Bioenergetic Strategies of the Cotton Rat, Sigmodon hispidus

Bioenergetic strategies of hispid cotton rats on a relict grassland in west-central Kansas were assessed for the period December 1967 through November 1968. Less than 1.0 per cent of the yearly net primary production of the grassland was ingested by cotton rats. Of the energy assimilated throughout the year, all but 2.2 per cent was utilized in maintenance. Energy flow channeled into secondary production ranged from a low of −2.4 kilocalories per hectare per day in January to a high of 22.6 in September. Accordingly, population density was at a low of 8.8 rats per hectare in April but increased to 19.4 by September. Seasonal fluctuations in relative amounts of energy utilized in secondary production probably reflect physiological adaptations to withstand adversities of climatic seasonality.

Genetic Relationships among Southwestern Populations of the Brazilian Free-Tailed Bat

Electrophoretic methods were used to test the hypothesis that migrationally distinct populations of Tadarida brasiliensis are distinct genetically. No fixed allelic differences were found, and genic differentiation among samples was slight. Excessive homozygosity within samples relative to that expected at Hardy-Weinberg equilibrium likely represents the Wahlund effect rather than inbreeding. Genetic relationships among southwestern populations of T. brasiliensis apparently are the result of at least some site tenacity of breeding populations but subsequent intermingling of gene pools in maternity and bachelor colonies.

Evolutionary and Taxonomic Relationships among North American Arid-Land Foxes

Relationships among nominal taxa of North American arid-land foxes were assessed by morphometric and protein-electrophoretic methods. Morphometric data distinguished between the kit fox ( Vulpes macrotis ) of the Southwest and the swift fox ( V. velox ) of the Great Plains but not among nominal subspecies of the two foxes. It was uncertain from the morphometric data whether the two foxes should be regarded as species or subspecies. Genic divergence was negligible, with two subspecies of the kit fox more similar genetically to the swift fox than to two other subspecies of the kit fox. We conclude, based on the genic data, that all arid-land foxes in North America pertain to one species, Vulpes velox . Based on the morphometric data, we conclude that two subspecies, V. v. velox and V. v. macrotis , should be recognized.

Natural History of the Brazilian Free-Tailed Bat in the San Luis Valley of Colorado

The natural history of Brazilian free-tailed bats, Tadarida brasiliensis mexicana (Saussure), in an atypical, predominantly male colony in south-central Colorado was investigated in 1982 and 1983. The colony inhabits the Orient Mine at the base of the Sangre de Cristo Mountains in the San Luis Valley. Iron ore was removed from the mine (elevation, 2,800–3,000 m) between 1881 and 1932. Colonization by free-tailed bats occurred no earlier than 1900 and most likely after the mine closed in 1932. The colony roosts in a cavernous underground stope in which ambient temperature varies from 6 to 12°C when bats are present from mid-June through October. At peak numbers, the colony consists of more than 100,000 bats. Outflights in both years lasted an average of nearly 1 h. Bats emerged earlier relative to sunset in late summer and autumn than in early summer. Timing of outflights was not affected by percent cloud cover. Outflights were dispersed in June and became more concentrated, often with serpentine components, later in the year. Capture samples taken with mist nets indicated that composition of the colony was 98% adult males until mid-August, when adult females and young-of-the-year became more common.

Historical Biogeography of Foxes in Kansas

The distribution and numerical status of each of the three species of foxes in Kansas have changed appreciably in the past century. Undocumented information suggests the red fox was common in parts of western Kansas, and therefore probably occurred statewide, at the time of settlement of the region by European Man. Populations west of the Flint Hills diminished or were extirpated by the end of the 19th century. Relict populations in the west or immigrants from the east, or both, possibly supplemented with individuals imported for sport hunting, began to reoccupy the former range in western Kansas (primarily in riparian habitats) by the 1930s, and in two or three decades the species dispersed essentially throughout the state. The species now is abundant in most areas, especially in southwestern Kansas. The swift fox was abundant in western Kansas when that region was settled in the mid-1800s. It became rare by the 1930s, but apparently was not extirpated. The decline in numbers and distribution ceased at about midcentury, and the species subsequently reoccupied much of its original distribution. Today, the swift fox is abundant on the High Plains of western Kansas. The gray fox was rare and occurred only in easternmost Kansas in the early 1900s, but became more numerous by about mid-century. It dispersed westward in riparian habitats associated with the Kansas and Arkansas river systems at about that time, and became relatively common in certain areas of western Kansas by the 1960s and 1970s. Subsequently, the species seemingly again became rare and its range possibly diminished eastward.

Systematic Relationships of Pocket Gophers (Genus Geomys) on the Central Great Plains

Taxonomic relationships of two supposed species, Geomys bursarius and G. lutescens , on the Central Great Plains were assessed using morphometric, bacular, karyotypic, and electrophoretic analyses. Only cranial size and pelage color proved useful in differentiating between the taxa in a zone of contact in Kansas, where no indication of morphometric intergradation was found. Populations of the same taxa in a zone of contact in Nebraska were distinct not only morphometrically but also karyologically and electrophoretically; however, results from all three data sets suggested introgression. These genetic data and the lack of concordance between zones of contact in Kansas and Nebraska indicate that the two taxa should be regarded as subspecies of G. bursarius rather than distinct species.

ASSOCIATIONS OF SMALL MAMMALS ON THE CENTRAL HIGH PLAINS OF EASTERN COLORADO

Small mammal associations were sampled in six habitats on the central High Plains of eastern Colorado. The habitats consisted of grazed and ungrazed riparian woodland, sand sage- brush, and shortgrass. Ordination analysis revealed that grazing had the least effect on small mammal associations in shortgrass and the greatest effect on associations in riparian woodland. Moreover, grazed sand sagebrush supports a mammalian fauna more nearly like that of shortgrass than that of ungrazed sand sagebrush. These observations on the effects of grazing are interpreted in terms of understory vegetation. The mammalian fauna of the semi-arid central High Plains has been less extensively investigated than have those of mountainous regions to the west or the subhumid prairie to the east. Small mammal associations on the cen- tral High Plains have been characterized for only three types of habitat- riparian woodland in northeastern Colorado (Beidleman, 1954; Archibold, 1964); upland communities in southeastern Wyoming (Maxwell and Brown, 1968); and northern shortgrass prairie in northeastern Colorado (Grant and Birney, 1979). The purpose of this study was to characterize small mammal associations at six sites, three grazed and three ungrazed, in eastern Colo- rado. Unlike Grant and Birney (1979), who described community structure of small mammals in nine different regions of North American grassland, our objective was to relate small mammal associations to attributes of their local environments within one region of the Great Plains.

BIOGEOGRAPHIC RELATIONSHIPS OF POCKET GOPHERS IN SOUTHEASTERN COLORADO

Biogeographic relationships of Pappogeomys castanops, Thomomys bottae, and Geomys bursarius were studied at the margins of their ranges in southeastern Colorado. The dis- tributions of P. (astanops and T. bottae overlap by nearly 5 km on Mesa de Maya but are allopat- ric below the mesa. In the zone of sympatry, where these two species occupy adjacent burrows in the same soils and vegetation, the average depths of their feeding burrows differ significantly. This relationship apparently represents an intermediate stage in competitive exclusion, which influen- ces the biogeography of P. castanops and T. bottae in southeastern Colorado. The distributions of P. castanops and G. bursarius overlap by nearly 65 km below Mesa de Maya, but this overlap represents parapatry rather than sympatry. The biogeographic relationship of P. castanops and G. bursarius in southeastern Colorado is the result of ecological specialization, agricultural activities, and the Dust Bowl of the 1930s.