Activity of an Amazonian aerial insectivorous bat depends more of food resources than vegetation structural complexity

Abstract

1 – Many studies have shown that insectivorous bats frequently use riparian zones around streams, but it is often unclear whether the bats are using those areas for feeding or are just making use of the uncluttered areas over streams as movement corridors. No study of Neotropical bats has investigated the relative use of riparian zones and areas far from streams for foraging. 2 – We studied the effects of vegetation structure and food availability on the activity of the aerial insectivorous bat Pteronotus parnellii near and far from streams in tropical rainforest in Reserva Ducke, Central Amazonia. 3- We used horizontal photographs of understory vegetation to quantify the degree of obstruction (clutter) by leaves and branches. Food availability was evaluated with small light traps designed to catch nocturnal insects. Bat activity was monitored with high-frequency sound recorders that operated continually for 60 hours at each site. 4 – In contrast to previous studies, most of which used mist nets, we found P. parnellii to be more active in places with dense understory vegetation, which were more common outside riparian zones. Food availability was also higher in places with more vegetation clutter. 5 – Generalizations in the literature, based on morphology, indicate that P. parnellii should be more active in sites with little vegetation clutter. However, we found the species to be more active in cluttered sites, indicating that food availability may be more important than clutter in determining where the bats foraged.