New study on acoustic groups of blue whales in the Indian Ocean

This is a new study that has just come out done by some fellow blue whale acoustic researchers. I have read this paper enthusiastically since it is very relevant to our work and my PhD research in Chile. It looks at the seasonal patterns of the different acoustic groups of blue whales in the Indian Ocean using the recordings from a network of hydrophones located at different points throughout the Indian Ocean basin (see map below).

Figure 2 from Samaran et al. 2013. Map of the Indian Ocean.

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Locations of the hydrophones used in this study are shown as black stars and location of previous recordings of blue whales calls are shown as white stars.

This work is based on the fact that different groups of blue whales can be divided up into acoustic groups based on their dialects: each group of blue whales has it own specific way of singing. But it is still not clear whether these acoustic groups reflect actual breeding populations and have separate geographical ranges. 

From hydrophones dotted around the Indian Ocean, Samaran et al. look at the degree of overlap of the different populations. It shows that although some overlap does occur, the different dialects, and therefore acoustic groups, largely occur at different sites or during different seasons.

This work is very similar to what we hope to achieve in Chile. We have first been working on characterising the Chilean dialect - or dialects - and then use this information to track the movements of these whales with a network of hydrophones that we have installed and now successfully recovered. We hope to share our findings soon, but we are still number crunching at the moment.