Bryde's whale ( ), or the Bryde's whale complex, putatively comprises three species of rorqual and possibly four. The "complex" means the number and classification remain unclear because of a lack of definitive information and research. The common Bryde's whale (Balaenoptera brydei, Olsen, 1913) is a larger form that occurs worldwide in warm temperate and tropical waters, and the Sittang or Eden's whale (Balaenoptera edeni, Anderson, 1879) is a smaller form that may be restricted to the Indo-Pacific. Also, a smaller, coastal form of B. brydei is found off southern Africa, and perhaps another form in the Indo-Pacific differs in skull morphology, tentatively referred to as the Indo-Pacific Bryde's whale. The recently described Omura's whale (B. omurai, Wada et al. 2003), was formerly thought to be a pygmy form of Bryde's, but is now recognized as a distinct species. Rice's whale (B. ricei), which makes its home solely in the Gulf of Mexico, was once considered a distinct population of Bryde's whale, but in 2021 it was described as a separate species.
B. brydei gets its specific and common name from Johan Bryde, Norwegian consul to South Africa, who helped establish the first modern whaling station in the country, while B. edeni gets its specific and common names from Sir Ashley Eden, former High Commissioner of Burma (Myanmar). Sittang whale refers to the type locality of the species.
Etymology In Japan, early whalers called it or . It preys on the anchovy and it was commonly associated with the skipjack. As modern whaling shifted to the Sanriku area, whalemen confused the sei whale with it; now only applies to the latter. Incidentally, anchovies are dominant prey for both species off Japan. They are now called , for their resemblance to the sei whale.Omura, Hidero. (1977). "Review of the Occurrence of the Bryde's Whale in the Northwest Pacific". Reports of the International Whaling Commission (Special Issue 1):88-91.
Taxonomy
The taxonomy is poorly characterised. The two genetically distinct, candidate species/subspecies/morphologies are Bryde's whale B. brydei and the Sittang or Eden's whale B. edeni, that differentiate by geographic distribution, inshore/offshore preferences, and size. For both putative species, the scientific name B. edeni is commonly used or they are simply referred to B. cf brydei/edeni.
In 1878, the Scottish zoologist John Anderson, first curator of the Indian Museum in Calcutta, described Balaenoptera edeni, naming it after the former British High Commissioner in Burma, Sir Ashley Eden, who helped obtain the type specimen. Eden's Deputy Commissioner, Major A.G. Duff, sent a Mr Duke, one of his assistants, to Thaybyoo Creek, between the Sittang and Beeling Rivers, on the Gulf of Martaban, where he found a whale, which had stranded there in June 1871 after swimming more than up the creek—it was said to have "exhausted itself by its furious struggles" to get free and "roared like an elephant" before finally expiring. Despite terrible weather, he was able to secure almost the entire skull and nearly all its vertebrae, along with other bones. These were sent to Anderson, who described the specimen, which was physically mature, as a new species.Anderson, J. (1878). Anatomical and Zoological Researches: Comprising an Account of the Zoological Results of the Two Expeditions to Western Yunnan in 1868 and 1875; and a Monograph of the Two Cetacean Genera, Platanista and Orcaella. Quaritch London. In 1913, the Norwegian scientist Ørjan Olsen, based on the examination of a dozen "sei whales" brought to the whaling stations at Durban and Saldanha, in South Africa, described Balaenoptera brydei, naming it after the Norwegian consul to South Africa Johan Bryde. In 1950, the Dutch scientist G.C.A. Junge, after comparing specimens of B. edeni and B. brydei with a , physically mature specimen that had stranded on Pulau Sugi, an island between Singapore and Sumatra, in July 1936, synonymized the two species into B. edeni.
In the 1950s it was discovered that there were two types of "sei whale" off Japan, a northern form with longer, finer baleen and shorter ventral grooves and a southern form with shorter, coarser baleen and longer ventral grooves. They also differed in the shape of the palate. The former was caught off northeastern Honshu and eastern Hokkaido, while the latter was taken off western Kyushu and southern Honshu. Both were caught off the Bonin Islands, but at different seasons. It was realized that the northern form were indeed sei whales (B. borealis), but the southern form were Bryde's whale (B. brydei/edeni). A later study revealed that Bryde's caught off Japan exhibited lateral ridges on their rostrum, whereas sei whales lacked this feature.
In the 1960s it was discovered that some of the "sei whales" being caught off Brazil were also Bryde's whales based on the same characters that distinguished the two species off Japan (i.e. three ridges on the rostrum versus one, shape of the palate, texture of the baleen, length of the ventral grooves).
Description Several differences in anatomy are found between Bryde's and Eden's whales; morphological similarities have caused confusions regarding species identification.SLAM - Sri Lanka's Amazing Maritime. New Great Whale: Eden's Whale in Sri Lankan Waters? . Retrieved on 3 August 2017
Size
Members of the Bryde's whale complex are moderately-sized rorquals, falling behind sei whales, but being larger than Omura's whale and the relatively small minke whales. The largest measured by Olsen (1913) was a female caught off Durban in November 1912, while the longest of each sex measured by Best (1977) at the Donkergat whaling station in Saldanha Bay, South Africa, were a female caught in October 1962 and a male caught in April 1963; both were the offshore form. At physical maturity, the coastal form off South Africa averages for males and for females, while the South Africa offshore form averages . The coastal form near Japan is slightly smaller, with adult males averaging and adult females . At sexual maturity, males average and females near Japan. Sexual maturity is reached at 8–11 years for both sexes in the offshore form off South Africa. At birth, they are .Evans, Peter G. H. (1987). The Natural History of Whales and Dolphins. Facts on File. The body mass of Bryde's whales can range . The bryde's whale is estimated to have weighed up to . The oldest living bryde's whale was 72 years old.
External appearance
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.
Bryde's whales closely resemble their close relative the sei whale. They are remarkably elongated (even more so than fin whales), with the greatest height of the body being one seventh their total length—compared to 1/6.5 to 1/6.75 in fin whales and only 1/5.5 in sei whales. Bryde's are dark smoky grey dorsally and usually white ventrally, whereas sei whales are often a galvanized blue-grey dorsally and have a variably sized white patch on the throat, a posteriorly oriented white anchor-shaped marking between the pectoral fins, and are blue-grey beyond the anus—although Bryde's off South Africa can have a similar irregular white patch on the throat. Bryde's have a straight rostrum with three longitudinal ridges that extend from the blowholes, where the auxiliary ridges begin as depressions, to the tip of the rostrum. The sei whale, like other rorquals, has a single median ridge, as well as a slightly arched rostrum, which is accentuated at the tip. Bryde's usually have dark grey lower jaws, whereas sei whales are lighter grey. Bryde's have 250–370 pairs of short, slate grey baleen plates with long, coarse, lighter grey or white bristles that are long by wide, while sei whales have longer, black or dark grey baleen plates with short, curling, wool-like bristles.
The 40 to 70 ventral pleats extend to or past the umbilicus, occupying about 58% and 57% of the total length, respectively; sei whales, though, have ventral pleats that extend only halfway between the pectoral fins and umbilicus, occupying only 45–47% of the total body length, whereas their umbilicus is usually 52% of the total body length. Both species are often covered with white or pink oval scars caused by bites from cookie-cutter sharks.Omura, H. (1966). "Bryde's whales in the Northwest Pacific". In Whales, Dolphins, and Porpoises (ed. K.S. Norris): 70-8. Univ. Calif. Press, Berkeley and Los Angeles.
Bryde's whales have an upright, falcate dorsal fin that is up to in height, average , and is usually between . It is often frayed or ragged along its rear margin and located about two-thirds of the way along the back. The broad, centrally notched tail flukes rarely break the surface. The flippers are small and slender.
Behaviour
Their blow is columnar or bushy, about high. Sometimes, they blow or exhale while under water. Bryde's whales display seemingly erratic behaviour compared to other baleen whales, because they surface at irregular intervals and can change directions for unknown reasons.
They usually appear individually or in pairs, and occasionally in loose aggregations up to 20 animals around feeding areas. They are more active on the water surface than sei whales, especially in coastal waters.
Breathing They regularly dive for about 5–15 minutes (maximum of 20 minutes) after four to seven blows. Bryde's whales are capable of reaching depths down to . When submerging, these whales do not display their flukes. Bryde's whales commonly swim at , but can reach . They sometimes generate short (0.4 seconds) powerful, low-frequency vocalizations that resemble a human moan.
Diet
Bryde's whales feed on a wide variety of fish, planktonic crustaceans, and cephalopods. In the western North Pacific, Bryde's whales caught by Japanese scientific whaling vessels (2000–2007) mainly fed on Japanese anchovy (Engraulis japonicus, 52%) and various species of euphausiid (36%, including Euphausia similis, E. gibboides, Thysanoessa gregaria, and Nematoscelis difficilis), as well as oceanic lightfish (Vinciguerria nimbaria, nearly 3%), and mackerels (Scomber spp., less than 2%). The prey differed by location and season. In coastal areas, euphausiids dominated the diet, comprising 89 and 75% of the diet in May and June, respectively. Further offshore, Japanese anchovy was the dominant species, accounting for nearly 100% of the diet in late summer.Tamura, T., Konishi, K., Isoda, T. and P. Okamoto. (2009). "Prey consumption and feeding habits of common minke, sei and Bryde's whales in the western North Pacific". NAMMCO/SC/16/MMFI/07 Based on the stomach contents of Bryde's whales caught by Japanese pelagic whaling expeditions in the North Pacific in the 1970s, the majority were found to feed on euphausiids (nearly 89%), whereas only about 11% fed on fish.
Off South Africa, prey preferences differed between the inshore and offshore forms. The former mainly feed on anchovies (Engraulis capensis, 83%), maasbankers (Trachurus trachurus, 36%), and pilchards (Sardinops ocellata, 33%), with only one (or 3%) being found with euphausiids (Nyctiphanes capensis). The latter, however, mainly feed on euphausiids (primarily Euphausia lucens, but also E. recurva, N. capensis, and Thysanoessa gregaria), as well as various deep-sea fish (including Mueller's pearlside, Maurolicus muelleri, and a species of Lestidium). One was even found "full of baby squid" (later identified as Lycoteuthis diadema).