Bryde’s Whale

Physical Description

Bryde’s (pronounced “broodus”) whales are members of the baleen whale family and are considered one of the “great whales” orrorquals. In general, Bryde’s Whales have a very broad and short head, with between 40 and 70 ventral grooves, and relatively large eyes. They can be recognised by the 3 parallel longitudinal ridges on the head,from the tip of the snout back to the blowhole.(The other rorquals have just one ridge.) They have a single 3 to 4 metre vertical blow. The prominently curved, pointed dorsal fin is readily seen when a Bryde’s Whale surfaces. The flippers are small and slender; the broad, centrally notched tail flukes never break the surface. Colour varies: the back is generally dark grey or blue to black, the ventral area a lighter cream, shading to greyish purple on the belly.

Length & Weight

Bryde’s whales typically reach a length of 13m, with a maximum of 15.3 m. Females are slightly larger than males. The color is variable, but usually the dorsal side is blueish black and the ventral side white or yellowish. A dark blueish grey area extends from the throat to the flippers. The flippers are slender and somewhat pointed. The dorsal fin is pointed and falcate (curved and tapering to a point; sickle- shaped). The ventral grooves extend to the umbilicus (navel). In the sei whale, the grooves end mid-body. A feature, unique to the Bryde’s whale is the presence of 2 lateral ridges that run from the tip of the snout to the blowholes, one on each side of the median ridge that is common to all rorqual whales. The baleen is about 19 cm wide and about 50 cm long. The inner margin is concave. They usually have 250-280 fully developed baleen plates.

Mating and Breeding

Females become sexually mature at about 12m in length, at which time they are probably 10 years of age (age determination based on laminations in the ear plug). Males become sexually mature at the age of 9-13 years (12 m in length). Gestation lasts about 1 year. New born calves are about 3.4 m in length. The calves are approximately 7.1 m when they are weaned at about 6 months. Females probably give birth less than once every two years.

Feeding

Bryde’s whales feed almost exclusively on pelagic fish (pilchard, mackerel, herring, and anchovies), pelagic crustaceans (shrimp, crabs, and lobsters), and cephalopods (octopus, squid, and cuttlefish).The Bryde’s whale consumes whatever shoaling prey is available and often exploits the activities of other predators, swimming through and engulfing the fish they have herded.They are therefore frequently found in areas of high fish abundance, along with seabirds, seals, sharks, and other cetaceans.

Distribution and Migration

Bryde’s whales are found in the Atlantic, Pacific, and Indian Oceans in warm temperate and sub-tropical waters.Populations exist mainly in warmer waters (20° C). They are not migratory, but they do move between inshore to offshore waters to follow food.

Natural History

Although generally seen alone or in pairs, Bryde’s Whales do aggregate into groups of 10 to 20 individuals on feeding grounds. The Bryde’s Whale appears to be livelier than most other rorquals and frequently breach clear of the water. Like Minke Whales, Bryde’s Whales will often approachvessels, allowing the characteristics to be confirmed. Diving behaviour is variable, depending on the prey being exploited, with dive depths varying from shallow to perhaps 300 m. Dive duration is usually 1 to 2 minutes, but may last as long as 10 minutes. Usually four to seven blows follow a longer dive. While feeding, the swimming speed of Bryde’s Whale is between 2 and 7 km per hour, but it can swim as fast as 20 to 25 km per hour (Kato 2002). Bryde’s Whales produce short powerful low frequency moaning sounds averaging 0.4 seconds in duration.

Status

Some populations were seriously depleted as a result of historical whaling practices. As a result of the 1986 Moratorium on Whaling, they are protected worldwide. Estimated Population: 40-80,000 animals (2000).

Acknowledgements
Australian Museum; American Cetacean Society; National Geographic Society; Department of the Environment, Water, Heritage and the Arts