Cetaceans or whales?

Cetacean refers to an order of marine mammals with a spindle-shaped body, anterior fins and a horizontal tail, but no hind limbs.

Whale is generally used to refer to any large cetacean; however, it is often used to refer specifically to baleen whales or members of the right whale family.

Cetaceans or whales?

Using scientific classification, whales, rorquals, dolphins and porpoises are all grouped together in the order cetacea. The word "cetacean" is derived from a Greek word meaning "sea monster." For us, all of these monsters are whales. They are divided into two groups: toothed whales and baleen whales. The toothed whales are by far more numerous and diversified, as much by their shape and size as their ecology. This group includes the sperm whale, narwhal, beluga, beaked whales as well as the dolphins and porpoises.

The baleen whales, suborder mysticete, are sometimes called "moustached whales." The name mysticete, which is also of Greek origin, refers to the resemblance between a moustache and the baleen plates suspended from the whale’s upper jaw. There are only 11 species of baleen whales worldwide: the rorquals (six species), the northern right whale, the southern right whale, the bowhead whale, the pygmy right whale and the grey whale. Some of these whales are the largest animals in the world, yet they feed mainly on small organisms. The rorqual whales use ingenious strategies to round up their prey before devouring them. The humpback whale has been known to surround its prey with a net of bubbles that it blows out through its blowholes, as it swims up beneath them. It then swims upwards to the surface with its mouth wide open. After taking a mouthful, it expels water between its baleen plates, which act like a sieve to retain the imprisoned prey.

Toothed whales, suborder odontocete, feed mainly on squid and fish that they capture one at a time. Each species employs a very distinct hunting method. The sperm whale can produce very powerful sounds that it uses to surprise, and possibly immobilize, its prey before swallowing them up. The beluga can pursue its prey from behind and, by simply opening its mouth, suck them in. It also uses its mouth as a siphon to draw in worms and other invertebrates buried in the muddy bottom. To attack large rorqual whales, killer whales hunt together like a pack of wolves.

The two groups of whales are also defined by their different types of social organization. The large rorqual whales and other baleen whales often seem to be solitary. They get together mostly during mating season and where food is abundant. By contrast, several species of toothed whales form complex societies. For killer whales, belugas and all of the dolphins, strong bonds bring together individual animals. These associations may be lifelong. The passing on of cultural knowledge and learning is very important for the cohesion of these social units. For the baleen whales, the strongest ties appear to be those observed between mother and offspring. For these species, ties rarely last more than a year.

Over the course of several months every summer, a herd of fin whales sojourns off Tadoussac in the St. Lawrence Estuary. Some animals come back year after year and are often seen together. Are these groups stable or temporary? For now the social organization of most species of baleen whales remains unclear. The results of long-term research programs and the use of new techniques in molecular biology to determine gender and filial relationships will certainly help to shed more light on whale societies.