Dolphins Use Sound to Navigate
The ability of bottlenose dolphins to use echolocation was discovered in the 1960’s, and in the following decade scientists learned that most odontocetes (toothed whales, dolphins and porpoises) have similar abilities. Since then, the echolocation capabilities of dolphins have been studied in considerable detail. We now have a good sense of the types of objects that can be detected, and how echolocation detection abilities are reduced by background noise. However, despite this knowledge about what odontocetes are capable of doing with echolocation, surprisingly little is known when and why they do in fact use it. Because dolphins are subject to eavesdropping by competitors, by fish, and even by potential predators when they echolocate, they may only use it when they really have to.
Research Associate Kathy Heise is leading a new study at the Vancouver Aquarium to better understand how dolphins use their echolocation to detect and capture prey and to avoid underwater hazards. With the assistance of experienced trainers, three Pacific white-side dolphins (Hana, Spin and Helen) are ‘blindfolded’ with gelatin eyecups and then left to wander freely through their habitat for up to ten minutes at a time. While they do so, their sounds are recorded and compared with sounds they make when their vision is not restricted.
Photo: John Healey
Pacific white-sided dolphin at the Vancouver Aquarium
More than a year was spent familiarizing the dolphins with eyecups so that they were comfortable wandering around their pool while wearing them. Recently, Kathy and the trainers began placing vertical lines suspended from floats that drift slowly through the pool while the dolphins had their eyecups on. She then recorded the dolphins’ sounds and behaviours as they swam through the pool, to monitor their use of echolocation. She plans to gradually introduce more complex objects, and will ultimately provide the dolphins with the opportunity to pursue live fish while blindfolded.
The ultimate goal of improving our understanding of how dolphins use echolocation is to improve fishing methods and gear in ways that reduce the accidental capture of dolphins, porpoises and whales in fishing operations worldwide.
Photo: John Healey
Spin swimming blindfolded around his habitat
with verticle ropes suspended in the background.