Of the many papers presented this week at the Institute of Electronic and Electrical Engineers/Marine Technology Society (IEEE/MTS) Ocean conference two really stood out as possible solutions to the impacts of communication signals on marine mammals. These papers discussed using bio-inspired or “bio-mimetic” signals as a model for communication signals.
In one case the model signals were ultrasonic dolphin bio-sonar clicks. The other was informed by the social whistles, squeaks, and chirps that dolphins use to chatter amongst themselves. The dominant incentive behind these techniques focused on how data communications could be covertly hidden in biological noises, but another benefit of biomimetic sounds is that using dolphin-like sounds would likely be less disruptive to marine life (except for those terrified prey animals that can hear the sounds of their dolphin predators).
The strategy of using biomimetic sounds is particularly germane this week as the International Whaling Commission issued a report on the stranding deaths of 100 melon headed whales in the Loza Lagoon system of Madagascar in May of 2008. The scientific research committee ruled out seismic airguns, disease, extreme tidal events, and earthquakes. It appears as if the most likely triggering event was high-power 12kHz multi-beam echo-sounder system used the day before the animals came into the lagoon and ultimately died.
This tragedy highlights a concern that it is not just military sonar and explosions that deafen and kill marine mammals, but other industrial signals being introduced into the sea as well. Increasingly high-energy acoustical signals of all sorts are being used for commercial and industrial purposes. The multi-beam sonar implicated in this stranding was part of a survey operation mapping the sea floor – probably for hydrocarbon extraction purposes.
Three of the ~100 melon headed whales stranded in the Loza Lagoon
The question arises about whether using dolphin-like clicks will confuse dolphins. But dolphins are adapted to extracting useful signals from the dense vocalizations of their kin. Having one more voice in the din probably wouldn’t clutter the sound field. If there is a disruption due to their hearing an aberrant signal it might be the dolphins wondering who was talking gibberish.
It was less than 100 years ago that humans began to use Sound Navigation and Ranging (SONAR) to visualize what was around them in the ocean. An advantage we had was that we found out about this technique from our “bio-sonar elders” – the dolphins, who have been using this way of perceiving their surroundings for 20-30 million years.
If we pay attention in class we may be successful in joining the bio-sonar clan – allowing us to sense and communicate through acoustic “data channels” while not disrupting the bio-acoustic community – which is a far better outcome than forcing animals out of the ocean with our reckless power.