Log Transcript

This is Genevieve Johnson speaking to you from the Odyssey in the Seychelles.

It seems as though the weather may finally have taken a turn for the better. With clear skies and a relatively calm sea, we spent several days this week tracking a large group of sperm whales. Although our research is focused primarily on data collection from that species, we do in fact collect data from every kind of cetacean (whale, dolphin and porpoise) we encounter.

As a part of our permit requirements in each country whose waters we survey, including the Seychelles, we submit a science report to local government officials detailing the findings of our research at the conclusion of each leg. IIn the past we have identified species of cetaceans in countries where they were previously undocumented. Thus, in exchange for being granted permission to conduct our research in the Exclusive Economic Zone (EEZ) of a specific country, we share information on cetacean sightings that usually includes species and abundance data.

In addition to encountering sperm whales this past week's leg, we also recorded sightings of Bottlenose dolphins, Pilot whales and an unidentified species of rorqual. All rorquals are large whales, the largest being the massive Blue whale, the smallest, the Minke whale. Rorquals are distinguished from other large whales by what appear to be throat grooves, but which is actually specialized, very elastic tissue that allows for an enormous volume increase in the whale's throat when it engulfs water holding its prey, and then filters that prey out of the water by ejecting the water through its baleen strainer. We first sighted the whale at about 1,000 meters from the Odyssey and although we could see at once that it was a rorqual whale, all rorquals spend a lot of time under water and are fast swimmers, often reappearing at the surface surprisingly far from where they dived. This one was no exception to those generalities and we never got a good enough look at to be sure of its species.

So how are researchers able to identify different species of cetaceans in the wild? This can sometimes be a challenge, as some species look very similar to one another, others like sperm whales and beaked whales spend long periods of time, indeed most of the time below the surface of the water, while high winds and rough seas, even the glare of the sun can add to the difficulties. However, there are several steps you can take that assist in making a successful identification. One feature alone is rarely enough, the key is to gather as much information on as many features as possible before attempting to draw a conclusion.

The blow of the largest of the rorqual whales, the blue whale, appears as a slender, vertical column of spray.

Photo: Judith Scott

Key features include size, color, body and head shape, position, presence or absence plus size and shape of the dorsal fin, distinctive features such as teeth, tusks, eye patches or stripes, fluke shape, fluke markings and in large species the characteristics of the blow. One seldom gets a good enough look to collect all or even most of this information, so in the end it becomes a process of elimination. The Odyssey crew is now so used to identifying sperm whales at sea, that we can identify most from a quick, glance, of a distant blow. The technique we use most often to identify large whales is to observe the characteristics of the blow. When whales come to the surface to exhale, air is blown out of their lungs under high pressure. There are several theories as to what makes the blow visible. Based on our own observations (although mostly of right whales) the most likely explanation is that the water overlying the blowhole as the whale blows is atomised into the cloud one sees. Another is that the sudden expansion of the warm, moist, air in the whale's lungs cools the air to such an extent, that the vapor in it condenses into mist (probably a more important contribution to visibility in polar seas than in the tropic seas we are in). The shape of what we call the 'blow' varies from species to species and is often the best method of identifying these animals at a distance.

All baleen, or filter feeding whales have a double blowhole, meaning they have two distinct nostrils, while largest toothed whale-the sperm whale, has but a single blowhole and instead of being located about a third a way from the tip of the whale's head it is located right at the front of the head (on the top left hand side-the latter being the reason that the blow of a sperm whale is projected forward and to the left). The characteristics of a baleen whale blow vary depending on the species. The blow we spotted at a distance today, led us to the conclusion that it was a species of rorqual, most likely a Bryde's whale. That is because the blow of a Bryde's whale is tall and thin, rising three to four meters in a single cloud-quite distinct from a sperm whale's low, bushy blow. But without seeing the features of the head one cannot make a positive identification so we had to record this sighting as being of an unidentified species-frustrating, but no expert can identify every cetacean he or she encounters.

With some practice, a little research into the natural history of cetacean species and a good cetacean identification guide, it is possible for anyone to identify the more common species and eventually even the more unusual species of whales.

Log by Genevieve Johnson