Boat noises disturb whales
When Chris Smith was little, his Dad used to laugh at the young Chris trying to wrap his tongue around the line “a noisy noise annoys a noisy oyster”. But a new paper out this month argues that noisy noises annoy humpback whales. Do the boats that take tourists out to watch whales - despite respectfully keeping a safe and sensible distance - nevertheless disturb the animals and potentially jeopardise their health, and the long-term health of the industry itself…? Chris heard the story from lead researcher Kate Sprogis...
Kate - So my name is Kate Sprogis and I'm a Marine mammal researcher and I'm an Australian, but I've been based in Denmark. When we did this study, we were trying to find out if the noise from vessels or boats impacted the behaviour of the whales.
Chris - Which sorts of whales?
Kate - We studied humpback whales because around the world, they are one of the whale species that are most common. They're also the target for whale watching, because they're so interesting to look at because they do a lot of breaching and pectoral slapping. And so we wanted to see if the noise from the whale watching boats impacted their behaviour or not.
Chris - When you say noise, is that people being rumbustious and sort of revelling on deck, or are we talking about the underwater noise made by moving bits of boat propellers and so on?
Kate - We looked at the noise from the boat engines because the whales stay underwater for most of the time, and that's the noise that they're hearing, and how they perceive their environment is through sound. Whereas ours is primarily through vision. So we use our eyes to interpret our environment, whereas whales and dolphins that live under the water primarily use sound.
Chris - And how did you actually monitor the change in the whale's behaviour and do it in a way that meant that by doing that monitoring you weren't changing the outcome of the experiment?
Kate - So how we set up our experiment was that we approached the whale with the vessel and we played back different noise levels. And to determine if the way or change their behaviour or not, we actually flew an unmanned aerial vehicle, or drone, above the whale at all times at an altitude of about 30 meters and we recorded video. So then we could see if the whale had changed its behaviour or not.
Chris - What sorts of changes in behaviour were you looking for? How did the whales respond?
Kate - Through the drone video what we were recording are the number of breaths the whale would take, and we would also record if the whale began moving. They would normally rest on the surface, and then if there was a change in behaviour, they would increase the number of breaths that they took, but they would also start swimming away. And this was reflected in the drone video.
Chris - And putting all this together then, how does the different levels of sound map onto what the whale's response is?
Kate - When we drove past the whale and we played back a quiet noise, the whale would continue sleeping on the surface. Whereas when we drove past the whale and we played back a loud noise from the boat, then the whale would actually change its behaviour. It would start swimming away from the vessel. And if you put that into a whale watching scenario, what you actually want is the whale to stay there so that the tourists on board can see the whale in an undisturbed way and not in a way that you know that they're being disturbed from your presence.
Chris - How does this compare the amount of noise that you produced with the amount of noise that a whale watching tourist boat would make? Was this a relevant level of sound intensity that you're exposing these whales to, and then seeing them change behaviour in this way?
Kate - Yes. So the noise that we played back was a vessel noise and it was within the range of other whale watching vessel noise that we have also recorded the noise levels from.
Chris - In other words then the boats that are going out there to take tourists to go and look at these wonderful creatures are nevertheless causing them disturbance. Is that the interpretation, and we should therefore give them some guidance about how not to do that?
Kate - Yeah. So right now on the whale watching guidelines globally, there are no noise emission standards. So a loud boat can be whale watching a whale at a hundred metre distance and then a quiet boat can also be at that same distance. However, the loud boat is going to have an impact on that whale, whereas the quiet boat won't. So if we can encourage that whale watching boats are quiet boats, then this is going to have less impact on the whales than a loud boat would.
Chris - And can you actually offer them some guidance as to what constitutes loud and quiet?
Kate - What we recommend is that vessels be quiet enough that the vessel is around the ambient noise level within the area. So vessels should be able to be recorded within the area so that they know what their source level, or the noise level of their boat, is.
Chris - You looked at humpback whales. Do you think this is true of other whales that people go and observe as well?
Kate - Yes, it can be used for other whale and dolphin species because they also use hearing as the primary sensory modality as they're underwater. So if there is a loud vessel, then they're going to be able to hear that loud vessel instead of seeing that loud vessel. So if they're a whale that is resting on the surface, then they're most likely going to be disturbed by a loud vessel compared to a quiet vessel.