The Lombard effect is the automatic and involuntary change in the intensity of vocalizations in the presence of background noise in order to maintain a constant signal to noise ratio. While this phenomenon is commonly found in vocalizing terrestrial vertebrates, it had not previously been examined in aquatic vertebrates such as fishes. This experiment tests the presence of the Lombard effect in the red-finned loach, Yasuhikotakia modesta, which make two types of sounds: butting and clicking. I recorded three pairs of Y. modesta during aggressive interactions over territory and compared the sounds produced in silence with sounds produced in the presence of background noise (approximately 120 dB re 1 µPa). An increase of approximately seven dB was found for maximum click amplitudes in the presence of background noise compared to those in quiet control conditions. Butting sounds did not change significantly in response to background noise. Aggressive behaviors that accompanied the sounds were also categorized, and were labeled as: chasing, circling, ramming, intimidation, lateral displaying, biting, and defending behaviors. This is the first study that presents evidence that the Lombard effect may be present in fishes.
Advisor(s) or Committee Chair
Dr. Michael Smith
Biology | Environmental Sciences
Coffey, Bethany, "Aggressive Acoustic Behavior in Yasuhikotakia Modesta: Does the Lombard Effect Hold Water?" (2012). Honors College Capstone Experience/Thesis Projects. Paper 346.