Andres Piedra, School of Natural Resources and the Environment, University of Arizona, Tucson, AZ 85721
Background/Question/Methods
Species richness varies along elevational gradients for several reasons, including changes in temperature, precipitation and vegetation. Typically, vegetation types supporting the most species, whether at high or low elevations, dictate richness-elevation patterns. However, human disturbance can influence the presence of some species and alter expected patterns of richness. Bighorn sheep recently were re-introduced in the Santa Catalina Mountains, in southern Arizona. The area where the sheep were released is popular with hikers, especially at low elevations. Vegetation at low elevations 2900-3400ft is dominated by saguaro cacti and palo verde trees, and generally supports more species than the bullgrass that occurs at higher elevations (4800-5300ft). I was interested in determining species richness along the elevational gradient spanning where the sheep reside. I used photos (~20,000) taken by 10 trail cameras placed along the elevational gradient to document species richness. For each animal photographed, I recorded species, time of day, and elevation.
Results/Conclusions
A total of 13 species were captured by the photographs, ten were located at high elevations, eight at middle elevations, and seven at low elevations. Most (85%) were active at night. Three species (e.g., mountain lion, ringtail cat, black bear) were detected only at high elevations, and only one species (e.g., pocket mouse) was detected only at low elevations, whereas about 30% of all species were detected at all elevations. I speculate that the mountain lion may be absent from the low elevation areas because the animals that provide the majority of their food, deer and bighorn sheep, are mostly located at the higher elevations.