Small mammal and herpetofauna communities and habitat associations in foothills of the Chihuahuan Desert
Jorgensen, Eric Edward
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Small mammal and herpetofauna habitat associations, communities, and habitat characteristics were sampled from 6 habitats associated with foothills of the Sacramento Mountains near the northern limit of the Chihuahuan Desert. Sampled habitats included arroyos and adjacent uplands under 3 conditions of physiography: upper, middle, and lower. Sampling was conducted during late spring and early fall, 1993-94. Eighteen species of heteromyid and murid rodents were captured. Abundance decreased 34% over the term of this study and 14 of 42 temporal effects were significant. However, rodent habitat associations remained stable. Twenty-six of 42 potential habitat effects were significant and only 12 of 126 habitat x time interactions achieved significance. Rodent diversity was highest within arroyos and physiographic effects were not detected. Habitats maintained their diversity relative to other habitats, though diversity decreased in all habitats over the period of this study. Presence or absence at a trap site was best explained by macrohabitat effects compared to microhabitat. Models classifying habitat capable of supporting high or low relative abundance, utilizing macrohabitat effects, achieved success rates in excess of 80%. Thirty species of reptiles and amphibians were captured. Herpetofauna did not partition use of arroyo or upland habitats, though power and effect sizes were low. The arroyo-upland contrast was primarily based upon vegetative characters. Post-facto analysis utilizing soil texture suggests that higher relative abundance of common herpetofauna species occurs on sandy substrata compared to stony substrata. For herpetofauna, soil texture may be a more important habitat factor than vegetation. Seeds, an important resource for desert rodents, were most abundant under grass and shrub covered microhabitats compared to sand and stone covered microhabitats. However, seed abundance was relatively equal between macrohabitats when occurrence of microhabitat was accounted for. Seed abundance displayed less temporal variation in arroyos, compared to uplands, and at lower physiography compared to upper and middle. There was a substantial lack of correlation between rodent relative abundance and seed abundance. The stability of seed resource availability in time may be important for some rodent species.