Investigating Tiger Hearing
Boys Town National Research Hospital, respected both nationally and internationally as the leader and hearing research, and the famous Omaha Henry Doorly Zoo are working together to help save endangered Tigers. How do these two organizations fit together? It’s in the research!
Edward Walsh, Ph.D., Director of the Development, Auditory and Physiology Laboratory at Boys Town National Research Hospital, received a grant of $200,000 per year for three years from the National Science Foundation to investigate hearing and vocalization in tigers. Dr. Walsh and his team are primarily concentrating on two calls; the confrontational roar and the territorial roar sometimes referred to as a moan. “The results support theories that tigers communicate with each other by infrasound—sound of lower frequency than most mammals perceive,” said Walsh.
If tigers can communicate through sound that cannot be detected by the human ear, there may be ways to deter these animals from villages, livestock and other predators, ultimately saving more tiger lives. Researchers have discovered that each tiger has a different range of infrasonic energy—just as no two people sound exactly the same. Devices that can pick up on the tiger infrasound may aid scientists in determining the correct census number of tigers in a given territory.
The Omaha Henry Doorly Zoo has built a permanent sound-proof bio-acoustics laboratory on site for Tiger conservation research. This $100,000 facility allows researchers to remain in close range with the tigers at all times, while the tigers remain in a setting they are familiar with.
“The effort the Henry Doorly Zoo has made in tiger conservation research is extraordinary,” said Dr. Walsh. “The sound booth has lead to acoustical findings that would not be apparent in a normal atmosphere.” In addition, Boys Town researchers are looking at identifying the dozen acoustic abilities that make up different tiger roars and moans. The booth also provides an educational opportunity for the public and raises awareness of tiger extinction.
The National Science Foundation Grant will provide opportunities for students to help collect additional data. Tiger conservation is the main goal of this acoustic research project, but it has opened the doors to many more studies down the road.
Studies have led to the discovery that the size of a tiger does have an effect on hearing; the larger the cat, the better he can hear. “We can begin to think of the many specialized studies that may steam from this research and one day have a refined understanding of how the human inner and middle ear may work in comparison to size,” said Dr. Walsh.
The Tiger Acoustic Investigation includes CT, CAT and MRI Imaging of the animals’ vocal track, inner and middle ear and includes the observation study of hearing behavior and the effects hearing has on brain function. A team on scientists from Boys Town National Research Hospital, University of Toledo, MIT, Harvard University, Creighton Medical Center and the Omaha’s Henry Doorly Zoo is conducting the research.