Bats are ecologically important species because of their role as pollinators, insect controllers, and seed dispersers. Many bat species are endangered and others are at risk due to habitat loss. Several studies have demonstrated the importance of desert streams and riparian areas as foraging and roosting habitat for bats. However, little is known about the species identity of bats that inhabit these habitats and how the species composition changes throughout the year. Our research objectives were to measure bat abundance and diversity along two desert streams before, during, and after the monsoon season. Using mist-netting techniques we examined temporal and spatial variability in bat activity along two perennial Sonoran desert streams in Arizona, the San Pedro River and Aravaipa Creek.
Nine bat species were captured along Aravaipa Creek and six species were captured along the San Pedro River, June through November 2008. Twenty-nine individuals were captured along Aravaipa Creek and nine individuals were captured along the San Pedro River. Bat activity was highest in September (late monsoon) along both streams with activity declining in October and November (post-monsoon). Female capture rate followed a similar pattern; six females were captured along both Aravaipa Creek and the San Pedro River during the monsoon, while only two females were captured along Aravaipa Creek post monsoon and no females were captured along the San Pedro River post monsoon. Along Aravaipa Creek, the most common species captured was the pocketed free-tailed bat (Nyctinomops femorosaccus; twenty four individuals were recorded), a relatively unstudied species. By examining temporal and spatial patterns in bat activity we can better understand bat foraging habitat requirements. With this information our research will improve conservation efforts and management decisions aimed at these ecologically sensitive species.