Frequency sensitivity and directional hearing in the gleaning bat, Plecotus auritus (Linnaeus 1758)

Area of Science:

• Auditory Neuroscience
• Bioacoustics
• Animal Behavior

Background:

• The common long-eared bat (Plecotus auritus) relies heavily on auditory cues for navigation and foraging.
• Understanding the neural basis of auditory perception in bats provides insights into sensory adaptation and evolution.

Purpose of the Study:

• To characterize the neural audiogram and auditory spatial receptive fields of Plecotus auritus.
• To investigate the role of the external ear (pinna) in auditory sensitivity and directionality.
• To correlate auditory system adaptations with foraging strategies in this species.

Main Methods:

• Recording neural audiograms from the inferior colliculus (IC) of Plecotus auritus.
• Measuring acoustical gain and directional properties of the bat's external ear.
• Analyzing the tonotopic organization of the central nucleus of the IC (ICC).

Main Results:

• Plecotus auritus demonstrates high auditory sensitivity, with best frequency thresholds below 0 dB SPL between 7-20 kHz.
• The external ear provides significant acoustical gain (up to 20 dB) and directional cues, particularly between 8-20 kHz.
• Neurones tuned to lower frequencies (<20 kHz) are disproportionately represented in the ICC, occupying 30% of its volume.

Conclusions:

• The auditory system of Plecotus auritus is highly adapted for low-frequency sound detection and precise spatial localization.
• The large pinna plays a critical role in enhancing auditory sensitivity and providing directional information.
• These auditory adaptations support the bat's gleaning foraging strategy, enabling effective prey detection through listening.