Abstract
Airborne and Underwater Hearing in the Great Cormorant (Phalacrocorax carbo) Studied with ABR and Laser Vibrometry
Ole Næsbye Larsen1, Tina Marie Huulvej1, Magnus Wahlberg1, Jakob Christensen-Dalsgaard1
1Department of Biology, University of Southern Denmark, Denmark
Background
Numerous studies have mapped the hearing abilities of birds in air, but currently there is little or no data, physiological, psychophysical or behavioral, on how diving birds hear or react to sound under water. Therefore, it is unknown whether the ears of diving birds are adapted to hearing under water and to what extent anthropogenic noise influences their hearing during a dive. In the present study, we measured the audiogram of cormorants in air and under water and compared the results to biophysical measurements of eardrum vibrations.
Methods
We obtained audiograms from wild-caught Great Cormorants (Phalacrocorax carbo) using auditory brainstem response (ABR) and measured eardrum vibrations using laser Doppler vibrometry (LDV). The ABR was measured first in a (150x100x80 cm) sound attenuated and anechoic box using three subdermal electrodes and, secondly, with its head and neck submerged approximately 10 cm under water in a (90x100x60 cm) water filled tank while being artificially ventilated. The ABR-response to calibrated tone bursts was measured at different intensities and frequencies (500, 1000, 2000, 4000, and 6000 Hz) to obtain hearing threshold values in air and under water. The bird was overdosed immediately after the last ABR. LDV measurements were obtained from reflecting foil on the eardrum first in an anechoic room and finally in the tank with the laser beam focused on the tympanal membrane placed 25 cm under water, and we obtained transfer functions of tympanal membrane motion in the frequency range 200 Hz to 10 kHz.
Results
The shape of the ABR audiogram follows the eardrum vibration transfer function. Both methods showed a clear peak with highest sensitivity at 1-2 kHz in air, while the most sensitive response was displaced towards lower frequencies (about 1 kHz) under water. In addition, the bandwidth of the water audiogram was only about half of that of the air audiogram.
Conclusions
The results suggest that cormorants have less sensitive in-air audiograms compared to other similar-sized birds. The hearing abilities in water are better than what would have been expected for a purely in-air adapted ear.
Funding
Supported by the Carlsberg Foundation 2009_01_0292
Ole Næsbye Larsen1, Tina Marie Huulvej1, Magnus Wahlberg1, Jakob Christensen-Dalsgaard1
1Department of Biology, University of Southern Denmark, Denmark
Background
Numerous studies have mapped the hearing abilities of birds in air, but currently there is little or no data, physiological, psychophysical or behavioral, on how diving birds hear or react to sound under water. Therefore, it is unknown whether the ears of diving birds are adapted to hearing under water and to what extent anthropogenic noise influences their hearing during a dive. In the present study, we measured the audiogram of cormorants in air and under water and compared the results to biophysical measurements of eardrum vibrations.
Methods
We obtained audiograms from wild-caught Great Cormorants (Phalacrocorax carbo) using auditory brainstem response (ABR) and measured eardrum vibrations using laser Doppler vibrometry (LDV). The ABR was measured first in a (150x100x80 cm) sound attenuated and anechoic box using three subdermal electrodes and, secondly, with its head and neck submerged approximately 10 cm under water in a (90x100x60 cm) water filled tank while being artificially ventilated. The ABR-response to calibrated tone bursts was measured at different intensities and frequencies (500, 1000, 2000, 4000, and 6000 Hz) to obtain hearing threshold values in air and under water. The bird was overdosed immediately after the last ABR. LDV measurements were obtained from reflecting foil on the eardrum first in an anechoic room and finally in the tank with the laser beam focused on the tympanal membrane placed 25 cm under water, and we obtained transfer functions of tympanal membrane motion in the frequency range 200 Hz to 10 kHz.
Results
The shape of the ABR audiogram follows the eardrum vibration transfer function. Both methods showed a clear peak with highest sensitivity at 1-2 kHz in air, while the most sensitive response was displaced towards lower frequencies (about 1 kHz) under water. In addition, the bandwidth of the water audiogram was only about half of that of the air audiogram.
Conclusions
The results suggest that cormorants have less sensitive in-air audiograms compared to other similar-sized birds. The hearing abilities in water are better than what would have been expected for a purely in-air adapted ear.
Funding
Supported by the Carlsberg Foundation 2009_01_0292
| Translated title of the contribution | Hørelse i luft og under vandet hos storskarven (Phalacrocorax carbo) studeret med ABR og laservibrometri |
|---|---|
| Original language | English |
| Publication date | 2014 |
| Number of pages | 1 |
| Publication status | Published - 2014 |
| Event | 37th Annual Midwinter Meeting of the Association for Research in Otorhinolaryngology: First-in-Human Studies of Neurotechnology: Past, Present and Future - Manchester Grand Hyatt, San Diego, United States Duration: 22. Feb 2014 → 26. Feb 2014 |
Conference
| Conference | 37th Annual Midwinter Meeting of the Association for Research in Otorhinolaryngology |
|---|---|
| Location | Manchester Grand Hyatt |
| Country/Territory | United States |
| City | San Diego |
| Period | 22/02/2014 → 26/02/2014 |