As big storms and massive swells swamp the coast of Western Australia, the theodolite team has taken cover for a few days and temporarily ceased observations. On lovely calm days it is possible to spot a blue whale blow from quite a few kilometers away, but when the sea is covered in whitecaps and has a six meter swell height it becomes pretty hard to spot even the largest whale! Not to mention the fact that it is pretty uncomfortable for the team sitting up on the open hilltop!
But although we are down, we’re not out! Data collection is continuing, despite the poor visibility. Because even if we cannot see the whales, we can hear them! Thanks to the supreme support of the Dunsborough Sea Rescue group, Curtin University has been able to deploy an underwater microphone (noise logger) in Geographe Bay each season for the last four years.
For the last three weeks a Curtin University noise logger has been sitting on the seabed just off Point Picquet, recording all the sounds in the ocean. The noise logger is capable of collecting an amazing variety of noise: ambient (waves, wind, rain), anthropogenic (human activities, vessels, construction work), and biological (shrimp, fish – and of course whales!). Because we are able to record the calls of passing whales, this allows us to keep monitoring their migration even when we are not present to provide visual ‘back up’ in the form of observational data. This type of data collection, when we listen to the whales and their environment, is known as Passive Acoustic Monitoring (PAM). Not only does it allow you to detect whales during poor weather, hours of darkness, or during low-visibility conditions, but it starts to give us an insight into whale behaviour beneath the ocean surface. And since whales spend the majority of their time submerged, that is a pretty important part of their lives to understand! We hope to continue noise logger deployments in Geographe Bay for years to come: if you would like to help support this work, please consider visiting the Donate page.
Last week, SouWEST researcher Dr Chandra Salgado Kent presented a scientific paper entitled “Passive acoustic monitoring of baleen whales in Geographe Bay, Western Australia” at the Australian Acoustical Society annual conference. This paper reported the data collected using passive acoustic monitoring in Geographe Bay between 2008 and 2011. It also described how this data is being used to monitor the migratory timing of baleen whales through Geographe Bay, characterise different whale vocalisations, and estimate how far away vocalizing whales can be detected during different levels of background noise. This helps us to understand how whales communicate and perceive important cues in their environment. If you would like a copy of this paper, please Contact Us.
Of course, visual observing still plays an important role – it is only through a combination of visual and acoustic monitoring techniques that we can gain a thorough understanding of how whales use Geographe Bay. In testimony to this, some of the more ‘hard core’ volunteers are still braving the weather to continue observations at Point Picquet. But their efforts are being rewarded, with the sighting of three blue whales (a single adult, then a mother-calf pair) passing through early this morning. Once we recover the noise logger in a couple of weeks and download the data, maybe we will be able to hear what the whales had to say about all this bad weather!