Abstract:

Ambient noise imaging ANI) between 8--80 kHz has been demonstrated to produce good images at 40-m range using a 3-m aperture. With the two classic forms of sonar, active and passive, marine mammal biosonar has always outperformed man-made sonar of comparable dimensions. It is then natural to ask whether marine mammals may also use this newly discovered ANI technique as part of their sensory arsenal. Twenty odontecetes, for example, may find advantage in not broadcasting their imminent presence in pursuit of an intelligent prey. An odontecete has been observed successfully pursuing live prey without vision and with no echolocation clinks detected on any of several monitoring hydrophones during pursuit. This surprising observation may be explained if biological ANI is a viable option. To test this idea, an ANI simulation model has been adapted to include realistic target responses of fish with swimbladders, and a model of the receiving performance of a tursiops dolphin has been used to evaluate the possible performance envelope of a biological ANI system. It is found that it is plausible that some marine mammals use ANI to augment information from other senses at short ranges. The implications for understanding these animals and their behavior are substantial.