December 15, 2017
Sounds from the Sea
- as seen by -Ricardo Antunes
In the quiet waters of Chiloé Island a Chilean dolphin rushed to break the surface.
It is one of the smallest cetaceans (whales, dolphins and porpoises) in the world. As suggested by the name, these dolphins are only found in Chile where they live in cold and shallow coastal waters.
I traveled there to record the sounds made by these dolphins. My colleagues and I spent two weeks on the Southeastern shores of Chiloé tracking these shy animals. Day after day, we tried to locate groups of dolphins and carefully positioned our little inflatable boat at the best spots to dip our hydrophones (underwater microphones) to record their sounds.
We analyzed the recordings to produce the first description of sounds made by Chilean dolphins. We found that these dolphins produce ultrasonic clicks – well above the human audible range – similar to those of other small cetaceans.
Sound recording instruments can be deployed over long periods and in remote locations to detect dolphin sounds and establish their presence. Knowing the types of sounds produced by this species is an import tool for monitoring their populations.
Similar to other coastal cetaceans around the globe, Chilean dolphins face a number of threats. They were hunted for food and bait in southern king crab and false king crab fishing. Their numbers are a fraction of what they used to be. While this practice in now illegal and appears to have lessened, it may still occur. A reliable assessment is currently lacking. Incidental entanglements in fishing gear and the development of salmon and shellfish farming in the dolphins’ habitat are also present threats to the survival of this species.
AUTHOR ACKNOWLEDGEMENTS: Thanks to collaborators Roke Rojas from Universidad Austral de Chile and Sonja Heinrich and Thomas Goetz from the University of St. Andrews in collecting scientific data and contributing to this publication on echolocation.