Tuesday, November 04, 2014
Roughly 23,000 humpback whales are making their annual southbound migration along Australia’s east coast to feeding grounds in the Antarctic. Mother and calf pairs swim south together from the breeding and birthing grounds inside the Great Barrier Reef, escorted by the male humpback whales who are famous for their songs. 93 humans have also gathered in Peregian Beach, preparing for a huge coordinated season of research studying these whales in a project called BRAHSS (Behavioural Response of Australian Humpback Whales to Seismic Surveys).
During the coming weeks, BRAHSS will be asking questions about how humpback whales respond to sound – specifically, what they do when images of what’s under the seafloor are created using something called a seismic array. A seismic array is a set of high-pressure air chambers towed behind a boat. When fired, the array releases powerful sounds. Those sounds travel through the water and down through layers of the seafloor. The sounds bounce off of different layers of material and reflect back toward the surface. Measuring the angles of the reflections creates an image, a map of what may lie under the ocean floor. These seismic sounds are often used in the search for energy resources.
Sound travels differently in water than in air, and whales are highly dependent on sound. We know that humpback whales communicate with each other, although the jury is still out on what they are saying. Males sing songs that change from year to year, and pass from one group to the next, like a hit pop song. All humpbacks, even the non-singing females and calves, make social sounds. There is even evidence to suggest that when the weather is windy and the ocean is noisier, whales might communicate more by leaping clear of the water, slapping back down with their heads, their long flippers, their tails, or, impressively, their entire bodies.
What whales do when humans add sounds to the ocean is a big unknown. It depends a lot on the species of whale, the kind of sound, how loud and how far away the sound is, and how quickly it gets loud. Imagine walking into a noisy room, versus being in a room that slowly gets noisy. Imagine spending a day in a cafe, or five minutes in a rock concert. As people and technology increasingly make noise under the waves, researchers all over the world are designing questions to tackle pieces of the ocean noise pollution puzzle.
Here in eastern Australia, there is a very predictable migration of humpback whales. It has been studied for decades, making this population of whales well-suited for asking new questions. Peregian Beach itself is a good location for studying underwater sounds. The seafloor here is simple and sandy, so sounds travel underwater in a way that’s relatively easy to measure. It lies along a long straight stretch where the whales migrate within sight of the shore. In total, there’s a big population of well-known whales, an area of ocean where sound travels in as simple a manner as can be asked for in nature, a predictable window of time in which the whales appear, and a straight stretch of land from which to watch – it’s the perfect set-up for a huge whale study. The area is tried and true – scientists have been doing whale work here for years, from land and sea. During BRAHSS 2014, an international team of researchers will muster daily to the field to gather the data and analyze it as it comes in, preparing it for study in the months and years to come.
The first week of BRAHSS is all about gearing up. 93 people disembarked from planes and trains, cars and buses. Backpacks were dropped into closets, boats were parked in the streets, and introductions began. Leaping straight into training, we volunteers are getting to know the gear, the data collection, and each other. To the north, humpback whales are swimming their way south toward Peregian Beach.
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