'Name that tune' algorithm used to identify signature whistles of dolphins

'Name that tune' algorithm used to identify signature whistles of dolphins

This is a very cool bit of research which has solved the long-standing problem of how to classify the very complex whistles of dolphins. Dolphin 'language' is so complex that is it very difficult to analyse using automatic detection software (like the kind I use for analysing blue whales songs). Up until now the only really successful way to analyse these very complex whistles was classifying them manually using the human eye, where researchers had to go through hours and hours of data and identify each whistle type. Some acoustic data sets can be thousands or tens of thousands of hours long, so this method was not very time effective at all.

Now, by applying the same kind of software used to recognise music, available on smart phone apps, researchers have been able to automatically identify and classify the signature whistles of dolphins, i.e. the characteristic whistles produced by each individual dolphin.

This is a very exciting step forward in the technology available to bioacousticians!

Noticias hoy en el Mercurio sobre nuestra investigación en la Ecorregion Chiloense

leer en: http://impresa.elmercurio.com/Pages/NewsDetail.aspx?dt=2013-10-10&dtB=10-10-2013+0%3A00%3A00&PaginaId=15&bodyid=1

Entrevista "Investigadora UdeC estudia los secretos del canto de la ballena azul"

http://www.udec.cl/panoramaweb2/2013/09/investigadora-udec-estudia-los-secretos-del-canto-de-la-ballena-azul/

Entrevista con Dr. Rodrigo Hucke-Gaete: "Actuamos como un país que no tiene científicos"

http://www.biobiochile.cl/2013/09/26/biologo-advierte-sobre-el-descuido-del-mar-chileno-actuamos-como-un-pais-que-no-tiene-cientificos.shtml

Whale mass stranding attributed to sonar mapping for first time

Whale mass stranding attributed to sonar mapping for first time

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. 

A new paper on blue whale response to military sonar

A new study by researchers in the USA (Cascadia Research, UC Santa Cruz, Duke, NOAA, US Navy) and the UK (Sea Mammal Research Unit and the University of St. Andrews) came out a few weeks ago which looks at the reaction of feeding blue whales to military sonar. This is the first of its kind looking at the response of baleen whales to sonar. This is a controversial issue since there is scientific evidence (and much media coverage) that suggests that sonar disturbs toothed whales (dolphins and beaked whales), damages their hearing, and could lead to disorientation and mass strandings. 

In baleen whales, concerns had been expressed that very low-frequency sounds (0-100 Hz, e.g. ship noise) that overlap with baleen whales' low-frequency vocalisations could disturb their communication, modify their behaviour and even damage their hearing. But up until now it was thought that mid-frequency sonar (3000-4000 Hz), being higher than the frequency range of baleen whale vocalisation and hearing, did not cause any disturbance in these larger whales.

This study does not link strandings in baleen whales to sonar but it is a significant contribution to better understanding the impact of sonar on these animals and does show, for the first time, that mid-frequency sonar does disturb blue whale feeding behaviour. This type of disturbance is significant in an animal which has a relatively short (5 months) but very intensive feeding season where whales must take in huge amounts of food to ensure enough energy for their long migrations and for withstanding the winter when food is scarce. Any persistent disturbance in feeding, due to sound pollution, the passing of a ship, or any other cause, could mean a significant loss of food and energy for these endangered animals.

This research was done by attaching tags with a suction cup (DTAGs) to the back of the whale. The tag records all the movements of the whale as it dives, looks for food and feeds, and therefore enables the researchers to build a 3D model of exactly what the whale is doing beneath the surface. There is a great video of this on the BBC website http://www.bbc.co.uk/news/science-environment-23115939. (Also take a look at a previous post on whale diving behaviour from a study by the same group of researchers.) 

So, this new study shows overall that sonar did modify blue whale diving behaviour to avoid the sound, which thereby interrupted feeding at depth. The researchers calculated that this disruption in feeding cost one whale 1 metric ton of lost krill, which is a lot of energy lost if the problem is persistent. Interestingly, however, whales that were feeding at the surface were not affected by the sonar, which indicates a complex relationship between whale behaviour and their response to sonar. 

This research shows that frequent use of military sonar in feeding grounds could be a significant problem for endangered blue whales.

You can read more about this and see the video on the BBC website: http://www.bbc.co.uk/news/science-environment-23115939 

Read the abstract of the paper at the Proceedings of the Royal Society website: http://rspb.royalsocietypublishing.org/content/280/1765/20130657.

And read more about the research group at Cascadia Research http://www.cascadiaresearch.org/socal-BRS.htm