| Bryde's Whales | |
|---|---|
| Size comparison against an average human | |
| Conservation status | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Subclass: | Eutheria |
| Order: | Cetacea |
| Suborder: | Mysticeti |
| Family: | Balaenoptiidae |
| Genus: | Balaenoptera |
| Species: | brydei edeni omurai |
| Binomial name | |
| Balaenoptera brydei Olsen, 1913 |
|
| Balaenoptera edeni Anderson, 1879 |
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| Bryde's Whale range | |
Bryde's whales ( /ˈbruːdə/ brew-də) are baleen whales, one of the "great whales" or rorquals. They prefer tropical and temperate waters over the polar seas that other whales in their family frequent. They are largely coastal rather than pelagic. Bryde's whales are very similar in appearance to sei whales and almost as large.
"Bryde" is sometimes misheard as "brutus whale". The name comes from the Norwegian consul to South Africa, Johan Bryde, who helped set up the first whaling station in Durban, South Africa in 1908.
They inhabit tropical and subtropical waters worldwide.
Bryde's whales are considered medium-sized for balaenopterids, dark gray in color with a white underbelly.
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The taxonomy is poorly characterized. Three genetically distinct, candidate species/subspecies/morphologies, Bryde's whale B. brydei, Bryde's/Eden's whale B. edeni,[2] and Omura's whale B. omurai,[3] differentiate by geographic distribution, inshore/offshore preferences, and size. For at least two of the species, the scientific name B. edeni is common. Omura's whale, a pygmy, is only recently described and reaches only 37.5–39 feet (11.4–12 m).[4]
They were not described until 1878, from a stranded specimen on the coast of Burma, which was given the name Balaenoptera edeni. In 1913, whales off the coast of South Africa were described as Balaenoptera brydei, the name being given to honour Johan Bryde, Norwegian consul and pioneer of the South African whaling industry.
By the 1950s, scientists grouped them in a single species, B. edeni, retaining Bryde's whale as the common name.
Females average over 42 feet (13 m), ranging between 40–50 feet (12–15 m). On average females weigh 26,400 pounds (12,000 kg), weighing up to 55,000 pounds (25,000 kg). Males are usually slightly smaller than females.[5]
The Bryde's whale is a baleen whale, more specifically a rorqual belonging to the same group as blue whales and humpback whales. It has twin blowholes with a low splashguard to the front. Like other rorquals, it has no teeth, but has two rows of baleen plates.
The head of Bryde's whales makes up about 25% of the body, with relatively large eyes. Each side of the mouth features 250–410 coarse gray baleen plates up to 40 centimetres (16 in) long. Forty to 70 ventral pleats are located on the animal's underside. Omura's whales have 180–210 baleen plates on each side and 80–90 ventral pleats. Bryde's whale is unique amongst rorquals in that it has three longitudinal ridges on its rostrum, from the tip of the snout back to the blowhole. Sei whales, with which they are often mistaken, like other rorquals, have a single median ridge. Omura's whales have no ridges.[4]
These whales have an erect, curved, pointed, "falcate" dorsal fin located far down its back and broad flukes. The dorsal fin is visible at the surface. The broad, centrally notched tail flukes never break the surface. The flippers are small and slender.[4]
Color varies: the back is generally dark grey or blue to black. The ventral area is a lighter cream, shading to greyish purple on the belly. Some have a number of whitish-grey spots, which may be scars from parasites or shark attacks. Omuras have asymmetrical head coloring, similar to fin whales.[4]
Their blow is columnar or bushy, about 10–13 feet (3.0–4.0 m) high. Sometimes they blow or exhale while under water. Bryde's whales display seemingly erratic behavior compared to other baleens, because they surface at irregular intervals and can change directions for unknown reasons.[4]
They usually appear individually or in pairs, and occasionally in loose aggregations of up to twenty animals around feeding areas.[4]
They regularly dive for about 5–15 minutes (maximum of 20 minutes) after 4–7 blows. Bryde's whales are capable of reaching depths up to 1,000 feet (300 m). When submerging, these whales do not display their flukes. Bryde's whales commonly swim at 1–4 miles per hour (1.6–6.4 km/h), but can reach 12–15 miles per hour (19–24 km/h).[4]
They sometimes generate short (0.4 seconds) powerful, low frequency vocalizations that resemble a human moan.[4]
These whales opportunistically feed on plankton (e.g., krill and copepods), and crustaceans (e.g. pelagic red crabs, shrimp), as well as schooling fish (e.g., anchovy, herring, sardine, mackerel, and pilchard). Bryde's whales use several feeding methods, including skimming the surface, lunging, and bubble nets.[4]
Bryde's whales breed in alternate years, apparently in any season, with an autumnal peak. Their gestation period is estimated at 12 months. Calves are about 11–13 feet (3.4–4.0 m) long at birth and weigh 1,000 kilograms (2,200 lb). They become sexually mature at 8–13 years of age, when females are 39 feet (12 m). The mother nurses for 6–12 months.[4]
Bryde's whales prefer highly productive tropical, subtropical and warm temperate waters of 61–72 °F (16–22 °C). Pygmies may prefer waters near the coast and continental shelf.[4]
Bryde's whales inhabit the Atlantic, Indian, and Pacific oceans, from 40° South to 40° North. Some populations migrate seasonally, moving towards higher latitudes during the summer and towards the equator during the winter. Uniquely among baleen whales, some populations do not migrate. The distribution of Omura's whales includes the nearshore and continental shelf waters of southeast Asia, east India, and the western Pacific.[4]
There may be up to 90,000–100,000 animals worldwide, with two-thirds inhabiting the Northern Hemisphere.
For management purposes, the U.S. population is divided into three groups: the Eastern Tropical Pacific stock (11,000–13,000 animals), Hawaiian stock (350–500), and Northern Gulf of Mexico stock (25–40). There are an estimated 12 animals in the waters off California, Oregon, and Washington,[4] where only a single confirmed sighting has been made (in 1991, off Central California) in the last couple decades.[6] The sighting is considered extralimital, just north of the species' normal range in the eastern North Pacific (about Sebastián Vizcaíno Bay, on the west coast of Baja California).[7] A whale watching tour out of Dana Point, California has twice claimed to have sighted Bryde’s whales, the first time on 12 March 2003 [8] involving four individuals, and the second on 6 September 2007[9] involving a pair of individuals.
There are insufficient data to determine population trends.
Bryde's whale is listed as Data Deficient by the International Union for the Conservation of Nature and Natural Resources (IUCN). It is also listed in Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) Appendix I, which prohibits international trade. Omura's whale is not listed by the IUCN.
The Bryde's whale is listed on Appendix II [10] of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). It is listed on Appendix II [10] as it has an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements.
In addition, the Bryde's whale is covered by the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (Pacific Cetaceans MOU).
Historically, this species was not significantly targeted by commercial whalers, but became more important in the 1970s as the industry depleted other targets. The Japanese hunt this species as part of their scientific whaling program. Artisanal whalers have taken them off the coasts of Indonesia and the Philippines.
Modern whaling for Bryde's whales is thought to have begun from coastal stations in Japan in 1906, where it continued uninterrupted until 1987—they were also caught offshore in the western North Pacific by both Japanese (1971–79) and Soviet (1966–79) fleets, as well as from Taiwan (1976–80), the Bonin Islands (1946–52 and 1981–87) and the Philippines (1983–85). In 1997 it was estimated that over 20,000 Bryde's whales had been caught in the western North Pacific between 1911 and 1987 (it was later learned that the Japanese had falsified their reported take from the Bonin Islands between 1981–87, reporting a catch of only 2,659 instead of the true take of 4,162). A population assessment done in the mid-1990s stated that the population in the western North Pacific may have declined by as much as 49% during 1911–96. Norwegian factory ships off Baja California took an additional 34 Bryde's whales between 1924–29;[11] two were also caught off central California in 1966.[12]
An estimated 5,542 Bryde's whales were caught off Peru between 1968–83, including a reported catch of 3,589 between 1973–83. An unknown number were also caught off Chile between 1932–79. Over 2,000 were caught off Cape Province, South Africa, between 1911–67, most (1,300) during 1947–67. The majority of the 2,536 "sei" whales caught by the pirate whaler Sierra in the South Atlantic between 1969–76 are believed to have been Bryde's whales. At least some Bryde's whales were among the 5,000 "sei" whales recorded in the catch off Brazil between 1948–77, but possibly only 8%.[1]
Over 30,000 Bryde's whales were caught between 1911–87, including over 1,400 taken by the Soviets in the Southern Hemisphere between 1948–73 (only 19 were reported).[13] The peak reported catches were reached in 1973–74 and 1974–75, when over 1,800 were taken each year. In 2000 the Japanese began implementing a scientific research program involving an annual catch of 50 Bryde's whales in the western North Pacific. Nearly 500 have been caught since the program began (as of 2009).[14]
Bryde's whales have not been reported as taken or injured in fishing operations. Bryde's whales are also sometimes killed or injured by ship strikes. Anthropogenic noise is an increasing concern for all rorquals, which communicate via low-frequency sounds.[4]
These whales are protected in the USA by the Marine Mammal Protection Act of 1972.[4]