Echolocating animals such as bottlenose dolphins depend on actively generated echolocation signals (termed clicks due to their extremely short duration) for ensonifying their environment and detecting and tracking prey. In contrast to how our own vision works, this means that the biosonar behavior of the echolocating predator directly affects how it senses the world – click faster, for example, and you get a faster update on how prey moves but you restrict yourself to looking for prey at shorter range. The environment that you are echolocating in, and the prey that you are searching for, may offer different challenges such as reflections from bottom or ocean surface, or high background noise levels, that animals need to deal with by making adaptive changes to their biosonar behavior. Using acoustic recording tags (DTAGs) we can measure echolocation signal parameters directly as animals search for and capture food in different environments.
In late August 2016, we were able to instrument three offshore bottlenose dolphins in Bermuda with suction-cup-mounted acoustic tags, as part of a study conducted by an international team from Dolphin Quest Bermuda, Chicago Zoological Society and L’Oceanografic in Valencia. These bottlenose dolphins live and feed in a completely open deep-water environment that provides a stark contrast to the shallow coastal habitat of Sarasota Bay dolphins. As a consequence, it looks like they are using echolocation signals that allow them to detect prey over longer ranges compared to the coastal dolphins of Sarasota – not a bad trick when looking for prey at several hundred meters depth. Over the next few years, these data in combination with tags from the Sarasota dolphins will help us understand exactly how animals adapt their biosonar to these acoustically different habitats and, in essence, to understand how flexible the bottlenose dolphin biosonar really is.
Funding for this project was provided by Dolphin Quest and Office of Naval Research YIP Award # N000141410563 to Dr. Andreas Fahlman.
This article appeared on page 12 of the 2017 SDRP Annual Report, Nicks n Notches.