Bryde’s whale (Balaenoptera edeni)
|Also known as:||Common Bryde’s whale, Eden’s whale, pygmy Bryde’s whale, tropical whale|
|French:||Baleinoptère De Bryde, Rorqual De Bryde, Rorqual D'Eden, Rorqual Tropical|
|Spanish:||Ballena De Bryde|
|Size||Male length: 13.7 metres (2)|
Female length: 14.5 m (2)
|Weight||16 – 18.5 tonnes (2)|
Classified as Data Deficient (DD) on the IUCN Red List (1) and listed on Appendix I of CITES (3).
Pronounced “broo-dess”, the Bryde’s whale is named after Johan Bryde, who helped construct the first South African whaling factory in the early 1900s (4). This species is often confused with the slightly larger sei whale(Balaenoptera borealis), but can be distinguished by the three distinctive ridges that run from the tip of the broad rostrum to the rear of the head, level with the two blowholes. Like other rorqual whales, the Bryde’s whale has numerous grooves running along the underside of the lower jaw to the belly, which allow this area to expand when the whale swallows water during feeding. The jaws are lined with between 250 and 365 plates of baleen, which bear long, coarse bristles on the inner edge, used for trapping food. The skin of the Bryde’s whale is black or dark grey, with white patches on the throat and chin, and may sometimes appear mottled due to pock marks caused by parasites and small sharks (2).
The taxonomic status of the Bryde’s whale is currently unclear. While there appear to be numerous different forms—occupying separate locations and habitats, and showing variations in size—a consensus has yet to be reached regarding whether they should be classed as subspecies or species (1).
The Bryde’s whale can be found in tropical and sub-tropical waters throughout the Atlantic, Pacific and Indian Oceans (1)
There appear to be two distinct habitat preferences amongst Bryde’s whales, with some populations, usually comprising smaller-bodied individuals, occurring in coastal waters, while other populations can be found in the open ocean (1) (5). Nevertheless, all Bryde’s whales have a preference for warmer waters above 16.3 degrees Celsius (1).
The Bryde’s whale can mostly be found alone or in mother-calf pairs, but on occasion loose aggregations may form, probably due to the proximity of a productive feeding ground (2) (4). The feeding behaviour of this species is spectacular, and involves the whale lunging forwards through a shoal of fish or krill, mouth opened wide. A vast quantity of prey and water is taken into its mouth, which is accommodated by the expandable region on the underside of the jaw. This is then squeezed back through the closed jaws of the whale, allowing water to escape through the baleen fibres, but trapping food, which is swept off by the huge, rough tongue and swallowed (2).
The Bryde’s whale is one of the livelier rorqual species, frequently breaching clear of the water, and commonly making one to two minute long dives between the surface and depths of 300 metres (2). Migration patterns vary, with coastal populations in tropical waters appearing to remain in the same location throughout the year, whereas populations in subtropical waters may make limited migrations in response to movements of prey (1) (5). In tropical waters, the Bryde’s whale may breed throughout the year, while in sub-tropical waters breeding mainly occurs in winter (5). After a year-long gestation period, a single young is born, already measuring around 4 metres in length. The Bryde’s whale becomes sexually mature at around 8 to 11 years, and has a lifespan of up to 50 years (2).
A long standing prohibition on the operation of factory ships north of 40°S, put in place to prevent hunting of rorqual whale’s at their lower latitude breeding grounds, allowed the Bryde’s whale to escape most of the historical exploitation of rorquals, as it occupies this region all year round (1). Only populations in the North Pacific may have been affected, as whaling vessels in this region were allowed to operate at lower latitudes, but even this threat was mitigated by the international moratorium on all commercial whaling implemented by the International Whaling Commission (IWC) in 1986 (1) (2). Although pelagic whaling by Japan was subsequently resumed in 2000, it is under scientific permit, and limited to catches of 50 individuals per year (1).
The main concern is that, while assessed as a single species, the Bryde’s whale appears to be abundant, but if it is in fact a complex of several separate species, some populations may be so small that they warrant threatened status and require conservation action (1).
The Bryde’s whale is included in Appendix I of CITES, making all international trade in this species illegal (3). With the current moratorium on commercial whaling in place, there appears to be little concern about the survival of this species. However, there is some concern that the moratorium may be lifted, leaving the Bryde’s whale open to exploitation (6).
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- Gestation: the state of being pregnant; the period from conception to birth.
- Rorqual: derives from the Norwegian word meaning ‘furrow whale’, and refers to the folds or grooves of skin below the mouth that are a characteristic feature of the Baleanopteridae family of whales.
- Rostrum: central, forward-projecting and occasionally long spine between the eyes of crustaceans.
- Subspecies: a population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.
- Taxonomic: relating to the science of classifying organisms, grouping together animals which share common features and are thought to have a common ancestor.
IUCN Red List (December, 2009)