Improving our sperm whale research

This year we started to use more gear to collect data on sperm whales 😊 Sperm whales can be sighted here in the Azores year—round, so… why not collect some data on them while we are out at sea?

Photo ID

Since 2010 photo ID has been collected on the sperm whales at Futurismo. Photo ID is done by taking a picture of the fluke when the sperm whale dives. Preferably the picture was taken right behind the sperm whale, and is when the tail is straight up in the air (see figure 1 below). One of the biologists who was working with us for 9 years up until last summer, Miranda van der Linde, made use of this method and published a paper identifying the individual sperm whales. She used not only flukes, but also dorsal fins to identify the sperm whales, and she managed to identify the different social units! You can find brief summary of her paper on our blog.

Acoustics

Sperm whales are divers and spend most of their time under water, usually between 70 and 90% of their lives in the Azores (Oliveira et al., 2014). They can dive up to about 2 hours in one go so, sometimes our lookouts have a harder time finding the sperm whales. Since sperm whales make very loud sounds when they dive, in search of squids, it is possible to hear them with the hydrophone a few miles away. This year we quite often used the directional hydrophone to be able to find the sperm whales by listening to them underwater! (see figure 2 and 3 below)

Once we found sperm whales, they were usually still in a foraging behaviour. This means that they spend about 8-10 minutes at the surface before they go for a foraging dive again, and this is when they start clicking. The clicks are what we are interested in!

According to the way the whale watching is done here in the Azores, the sperm whale is always approached from the back, which makes every recording of the individual easier.

When the sperm whale went for a dive, we used a hydrophone to record the sounds (see cable hanging in the water in figure 4). The hydrophone to collect acoustic data was a little different than the directional hydrophone to search for the sperm whales, as described in the previous section. The difference between the two hydrophones is explained in our previous blog. Fadia Al Abbar prepared a proposal to set up a PhD on the acoustic behaviour of sperm whales and was interested in these recordings after the sperm whale dove. With a hydrophone set of Wageningen University, and a recorder, 2 GPS’s and a lens extender donated by the grant of IDEA WILD, the team was able to collect the acoustic data, photo ID of the individual being recorded, and the location. We managed to record the foraging clicks, and sometimes we even had some codas! Codas are a sequence of clicks that the sperm whales emit to socialize amongst each other.

Here’s an example of our recording of codas:

However, there were often so many sperm whales underwater that it was very difficult to tell which sperm whale was clicking! We would often see only one at the surface and once we were listening to the hydrophone, it was a whole orchestra of sperm whales clicking. That sounded like this:

Then, we also recorded our famous male sperm whale called Mr. Liable. Male sperm whale clicks generally sound a little different than the females. As you can tell, this sperm whale was also alone as he was the only one clicking. His clicks sounded like this:

Learn more about the different types of clicks that the sperm whales can emit, and why.

Surface behaviour

Along with the acoustic data collection, an Msc. Student from the University of Algarve, Ramona Negulescu, collected surface behaviour of the sperm whales observed from the whale watching vessels (see figure 5 and 6). This was not an easy task! Several methods were tested by her; using a clicker, and a behavioural sheet to collect data. Eventually, the best method used was with a voice recorder, so this was used throughout the rest of the data collection.

She recorded the behavioural reactions of the sperm whales to the boats. Very often the reactions were not very clear. Some of the preliminary observations show that when there was a pod of sperm whales surfacing, most of them would dive around the same time. Therefore, we sometimes saw the sperm whales diving when the boat was approaching. However, it is hard to prove whether it was a reaction to the boat and they were diving prematurely, or whether the sperm whale was ready to dive again. The blow rate was recorded as well, to see if the blow rates differed in certain conditions. Ramona is currently writing her report, and Laura González, her co-supervisor and head of biologists, is examining it, so we will see what the results will bring us!

Written by Fadia Al Abbar

Bibliography:

Oliveira, Cláudia Inês Botelho de. “Behavioural ecology of the sperm whale (Physeter macrocephalus in the North Atlantic Ocean”. 2014. VI, 123 p.. (Tese de Doutoramento em Ciências do Mar, especialidade em Ecologia Marinha). Horta: Universidade dos Açores, 2014.

Recorders and GPS’s used for the research were donated by IDEA WILD and a hydrophone set was used through the Wageningen Marine Research, the Netherlands.