Continuous vigilance by echolocating bottlenose dolphins (Tursiops truncatus) for up to fourteen days.

Abstract

The dolphin’s ability to actively detect randomly presented targets via echolocation for three, continuous, 5‐day sessions and a single 14‐day session was investigated. During each experimental session, a dolphin was required to ensonify the perimeter of its floating enclosure and report the presence of phantom echo generated (PEG) targets by pressing a response paddle. PEG targets were generated by convolving the dolphin’s echolocation signal with the impulse response from a metallic sphere. The resulting PEG target was delayed in time and projected back to the dolphin to simulate the echo of a “real target.” PEG targets varied in simulated range, location, and time of occurrence. Percent correct for target detection were 97, 99, and 100 for dolphin A and 75, 78, and 86 for dolphin B, during each 5‐day session, respectively. During a 14‐day session, dolphin A reported 98% of the targets correctly. False alarm rates were low and there was no significant effect of range or inter‐trial‐interval on percent correct or response time. The results indicate that dolphins are capable of continuously monitoring their environment via echolocation for multiple days (at least 14 days) and can accurately report the presence of regularly occurring targets.