Taxonomy & Nomenclature
Physical Description / Field Identification
The Bryde’s whale reaches fourteen meters, females being larger than males. Adults can be up to 15.5 m long; newborns about 4 m. Maximum weight is 20-25 tons. Coloration is typically gray dorsally and white ventrally, although sometimes banding or chevrons are present. Three distinctive ridges run from the blowhole to the tip of the snout on the whale’s rostrum. The dorsal fin of the Bryde’s whale is prominently sickle shaped, large (nearly 46 cm tall), and located about two-thirds of the way down the whale’s back. Bryde’s whales have between 40 and 70 ventral grooves and possess 250 to 370 baleen plates. The height of the blow is variable and Bryde’s whales often exhale underwater, then surface with little or no blow.
There are two genetically distinct types of Bryde’s whales, the standard and pygmy forms (the latter often called the Sittang whale). Pygmy-form Bryde’s whales are generally no longer than about 12 m. These are apparently different species, but their formal splitting awaits further taxonomic work and determination of the affinities of type specimens. The Sittang whale and standard Bryde’s whale are each more closely related to the sei whale than they are to each other.
Can be Confused With
The Bryde’s whale might be confused with its cogeners, the fin whales (B. physalus) or sei whales (B. borealis). However, the Bryde’s whale is the only member of its genus to have three medial ridges on its head; all other members of the genus have only one. Additionally, the Bryde’s whale's dorsal fin is tall and falcate and generally rises abruptly out of the back, a feature that will help distinguish this species (and sei whales) from fin whales, in which the dorsal fin rises at a relatively shallow angle from the back.
Distribution
The Bryde’s whale is primarily found in tropical and subtropical regions, rarely being seen poleward of 40° in either hemisphere. Bryde’s whales are often seen near shore in areas of high productivity, such as upwelling waters near oceanic islands and continental slopes; although they use offshore waters as well. There is some evidence that Bryde’s whales migrate, but not as markedly as other large whales. They are known to be year-round residents in some regions, such as in the Gulf of California.
Little is known about the distribution of Bryde’s whales in the western Atlantic Ocean. They have been found on the coasts of the southeastern United States and southern West Indies, in the Gulf of Mexico and southeastern Caribbean, and near Cabo Frio, Brazil. In the eastern Atlantic Ocean, Bryde’s whales have been seen from the Straits of Gibraltar south past the Cape of Good Hope.
Within the Indian Ocean, Bryde’s whales are found from the Cape of Good Hope to the Persian Gulf, Gulf of Martaban, the shores of Burma, all the way to Shark Bay, Australia.
In the western Pacific Ocean, sightings occur from the waters of northern Hokkaido, Japan, south to Victoria, Australia and North Island, New Zealand. In the Eastern Pacific Ocean, Bryde’s are found from southern California to Iquique, Chile.
Ecology and Behavior
Bryde’s whales are generalists in terms of habitat. They are also unusual in that they only mildly exhibit the seasonal breeding/migrating pattern typical of the balaenoptera. Studies indicate that they breed throughout the year in some locations. Females are sexually mature at about ten years, while males are mature at between nine and thirteen years. Females calve every two years, with gestation lasting about twelve months and lactation thought to last six months. The life span of the Bryde’s whale is unknown.
Feeding and Prey
Little is known regarding the foraging of Bryde’s whales. They are the only large whale known to feed extensively in warm waters of the world. Bryde’s whales target schooling fish in coastal areas and euphausiids (krill) offshore. Individuals or small groups target schooling fish that occur in spatially and temporally predictable patches. Bryde’s whales are known to surface feed and forage at depth by lunging.
Bryde’s whales have a broad diet dominated by: Fish > crustaceans.
Known prey species include:
Fish: Engraulis encrasicolus, Engraulis australis, Sardinops sagax, Trachurus trachurus, Engraulis japanicus
Crustaceans: Euphausia recurva, Euphausia lucens, Nyctiphanes capensis, Thysanoessa gregaria, Euphausia diomedae, Euphausia similis
Cephalopods: Lycoteuthis sp.
Threats and Status
Main threats to Bryde’s whales include:
• Harvest (whaling)
• Fisheries bycatch
• Entanglement in debris/fishing gear
The Bryde’s whale is a poorly studied species. The IUCN classifies the Bryde’s whale as “Data Deficient”, that is, there is not enough information regarding this species to assess its conservation status. The Japanese have included Bryde’s whales in their scientific whaling program in recent years, inciting international controversy. Additionally, small numbers of pygmy Bryde’s whales have been killed by artisanal whalers from villages in Indonesia and the Philippines.
Links
References
Andersen, M. 1998. The occurrence and distribution of the Sittang whale (Balaenoptera edeni Anderson, 1878) in Thai waters with remarks on osteology. International Whaling Commission, Research Paper NPWP1 (unpublished).
Bowen, W.D. and D.B. Siniff. 1999. Distribution, Population Biology, and Feeding Ecology of Marine Mammals. Pages 423-485 in Reynolds III, J.E. and S.A. Rommel, eds. Biology of Marine Mammals. Smithsonian Institution Press, Washington, DC.
Boyd, I.L., C. Lockyer and H.D. Marsh. 1999. Reproduction in marine mammals. pp. 218-287 in: J.E. Reynolds III and S.A. Rommel, eds. Biology of Marine Mammals. Smithsonian Institution Press, Washington, DC.
Cummings, W.C. 1985. Bryde’s whale Balaenoptera edeni Anderson, 1878. pp. 137-154 in S. H. Ridgway and R. Harrison, eds. Handbook of marine mammals, Vol. 3: The sirenians and baleen whales. Academic Press.
Kato, H. 2002. Bryde’s whales Balaenoptera edeni and B. brydei. pp. 171-177 in W.F. Perrin, B. Würsig and J.G. M. Thewissen, eds. Encyclopedia of marine mammals. Academic Press.
Leatherwood, S. and R.R. Reeves. 1983. The Sierra Club handbook of whales and dolphins. Sierra Club Books, San Francisco, California.
Perrin, W.F., M.L.L. Dolar and E. Ortega. 1996. Osteological comparison of Bryde&rsquols whales from the Philippines with specimens from other regions. Reports of the International Whaling Commission 46:409-414.
