Herpetofauna associated with arroyos and uplands in foothills of the chihuahuan desert

Arroyos form distinctive habitats in desert foothhills. To document herpeto faunal habitat associations with arroyos we operated 16 drift fences (eight in arroyos, eight on uplands) for 4,152 drift fence nights during spring a nd fall, 1993-1994. Only Scaphiopus couchii demonstrated an association for arroyo habitat, and only during fall 1993. Cnemidophorzus mannoratus and C . exsanquis demonstrated possible seasonal associations with uplands. Stati stical tests are characterized by low power, apparently resulting from smal l observed differences in relative abundance between habitats. Small observ ed differences suggest that, with some exceptions, arroyos versus uplands i s not a habitat contrast of relevance to herpetofauna. A posteriori canonic al correspondence analysis was applied to produce an ordination of species with six structural habitat variables (shrub cover, grass and forb cover at two heights, amount of detritus, stones and rocks, and sand on the substra te). This comparison, although suggesting a tendency for herpetofauna to fa vor arroyos, failed to show a significant relationship between herpetofauna and environmental variables. This study suggests that environmental variab les other than those directly related to vegetation will be important deter minants of herpetofaunal habitat suitability.