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4 - 26 <br />4.3.4 SMALL MAMMALS <br />• A quantitative small mammal trapping program was carried out during July and November, <br />1977. The objectives of the study were to obtain information on habitat affinity, species <br />diversity, and relative abundance within several distinct habitat types. <br />At each site sampled, 25 live traps were positioned linearly through what was judged to be a <br />homogeneous habitat. Traps were spaced at 10 CM intervals and checked on two consecutive <br />mornings. The results of all captures, including recaptures, are expressed as a trapping index <br />(fable 4.3.3); a standard procedure which facilitates comparisons with data gathered elsewhere. <br />The diversities and abundance levels obtained are rather low, but not uncommonly so for <br />the generally acid environment of the lease location. Numerous captures of deer mice are not <br />all uncommon. This is one of the more ubiquitous mammals. In contrast, the westem harvest <br />mouse is rarely captured in this geographic region. The canyon mouse is aptly named and <br />typically occurs among rimrock situations in westem Colorado. Species of the genus Microtus <br />were not taken. These are important prey species which are at times abundant. Whether they <br />reach high numbers in this area during some years is unknown. One reason for the general <br />• scarcity of raptors may have been related to the low population of these rodents. <br />The habitat affinities of all mammals identified are shown on Table 4.3-4. Laboratory <br />identifications of cottontails were not made, since this requires collecting specimens and <br />examining skull morphology. Probable identifications are based upon habitat occurrence. <br />Woodrat nests were observed at many sites, but no specimens were captured for identification. <br />The identification of the westem harvest mouse is based on osteological and pelage <br />characteristics. There is no question regarding its proper identification. The nomenclature used <br />for mammals follows Armstrong (1972). <br />• <br />Nlo Volume 1 4 - 29 - 96 <br />