Big brown bats (Eptesicus fuscus) emit intense search calls and fly in stereotyped flight paths as they forage in the wild
Abstract
The big brown bat, Eptesicus fuscus, uses echolocation for orientation and foraging, and scans its surroundings by aiming its sonar beam at obstacles and prey. All call parameters are highly adaptable and determine the bat's acoustic field of view and hence its perception of the echo scene. The intensity (source level) and directionality of the emitted calls directly contribute to the bat's acoustic field of view; however, the source level and directionality of the big brown bat's sonar signals have not been measured in the field. In addition, for bats, navigation and prey capture require that they process several streams of acoustic information. By using stereotypic flight paths in known areas, bats may be able to reduce the sensory processing load for orientation and therefore allocate echo processing resources to prey. Here we recorded the echolocation calls from foraging E. fuscus, in the field with a microphone array and estimated call intensity and directionality, based on reconstructed flight trajectories. The source levels were intense with an average max SL of 138 dB (rms re 20 µPa at 0.1 m.). Further, measurements taken from a subset of calls indicate that the echolocation signals in the field may be more directional than estimated in the lab (half amplitude angle=30° at 35 kHz). We also observed that E. fuscus appear to follow stereotypic flight paths, and propose that this could be a strategy to optimize foraging efficiency by minimizing the sensory processing load
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Jan 01, 2015
- Source ID
- 10.1242/jeb.128983
Entities
People
- Annemarie Surlykke
- Cynthia F. Moss
- Katrine Hulgard
- Lasse Jakobsen
Organizations
- Air Force Office of Scientific Research
- Natural Sciences, Danish Council for Independent Research
- Office of Naval Research
- Oticon Foundation in New Zealand