Decreased ability to acquire food of a captive deaf dolphin (Tursiops truncatus): Slower reaction times and lower success rates

Oceanic anthropogenic noise, such as naval sonar, can cause temporary hearing loss in cetaceans, but it is not known to what extent hearing loss affects cetacean behaviours such as feeding. This study used a captive deaf Atlantic bottlenose dolphin (Tursiops truncatus) to test the hypothesis that hearing loss would decrease a dolphin’s ability to acquire food by preventing echolocation (using echoes to locate fish). Reaction time (time to acquire dropped fish) and success rate (percentage of successfully acquired fish) were measured for the deaf dolphin and for two dolphins with no known hearing disabilities at Dolphins Plus in Florida in May 2009. The deaf dolphin had a significantly slower mean reaction time and a significantly lower mean success rate than those of the two other dolphins. A hydrophone suggested that the deaf dolphin could not echolocate, and thus relied mainly on vision. The results illustrate that hearing loss can negatively affect a dolphin’s ability to acquire food. Therefore, sources and effects of dolphin hearing loss require further investigation in order to provide targets for anthropogenic noise levels