A method to enable a bottlenose dolphin (Tursiops truncatus) to echolocate while out of water

Abstract

The study of site-specific brain activity associated with dolphin echolocation has been hampered by the difficulties inherent in administering radiolabels and performing medical imaging while a dolphin echolocates in an aquatic environment. To overcome these limitations, a system has been developed to allow a bottlenose dolphin to echolocate while out of the water. The system relies on a "phantom echo generator" (PEG) consisting of a Texas Instruments C6713 digital signal processor with an analog input/output daughtercard. Echolocation clicks produced by the dolphin are detected with a hydrophone embedded in a suction cup on the melon, then digitized within the PEG. Clicks exceeding a user-defined threshold are convolved with a target impulse response, delayed, and scaled before being converted to analog and transmitted through a sound projector embedded in a suction cup attached to the dolphin's lower jaw. Dolphin in-air echolocation behavior, inter-click intervals, and overall performance were analogous to those observed during comparable underwater testing with physical targets, demonstrating that the dolphin was indeed performing an echolocation task while out of water.