Meeting Abstract

18.2  Saturday, Jan. 4 10:30  Migratory Predators Adjust Foraging Behavior in Response to Migratory Prey KRAUEL, J.J.*; MCCRACKEN, G.F.; Univ. of Tennessee, Knoxville; Univ.of Tennessee, Knoxville jkrauel@utk.edu

Little is known about interactions between migratory predators and migratory prey, although these systems may be at high risk to disruption due to habitat loss and climate change. Migratory Brazilian free-tailed bats (Tadarida brasiliensis) track resources in time and space and consume migratory noctuid moths to fuel the bats’ own energy needs. During migration, moths fly at high altitudes in layers representing favorable temperature and wind direction, resulting in prey concentrations that might be detected by bats. However, these events have not been linked to shifts in foraging behavior of bats. We predicted bats will alter foraging patterns by flying at higher altitudes during moth migration than at other times, and bats will adjust echolocation calls with altitude and levels of moth activity. We flew a Helikite near Frio cave, Texas, on 13 nights in fall 2012 representing 3 levels of moth migratory activity. We used SM2Bat ultrasonic detectors to record bat passes at ground level and two altitudes (approx. 100 and 200m). Bat passes were assigned to species and parameters were measured on high-quality calls using Sonobat 3. 1,104 bat passes were confirmed as T. brasiliensis. Bat activity was proportionally higher at higher elevations than ground level during moth migration events (chi sq = 6.36, DF = 2, p = 0.042). In a PCA of call parameters, PC1 explained 30% of variation and consisted primarily of variables describing duration, amplitude, and bandwidth. PC1 differed significantly with altitude (Anova, F = 50.33, p = 0) and with the interaction of altitude and moth activity (F = 5.26, p = 0.005). Results support predictions that migratory bats change both foraging behavior in response to seasonal availability of migrating insect prey.