Tuesday, February 28, 2012

Life of Bryde's whale

Life of Sea | Bryde's whale (Balaenoptera brydei) | Bryde's whales are baleen whales, 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. This species has a circumglobal distribution and is found in the Atlantic, Pacific, and Indian oceans. Bryde's whales are found both offshore and near the coast in many areas, and tend to inhabit areas of unusually high productivity. They extend into some enclosed seas, such as the Persian Gulf and Red Sea.
Scientific classification
Kingdom:     Animalia
Phylum:     Chordata
Class:     Mammalia
Subclass:     Eutheria
Order:     Cetacea
Suborder:     Mysticeti
Family:     Balaenoptiidae
Genus:     Balaenoptera
Species:     brydei, edeni, omurai

For many years, whalers and field observers did not distinguish between Bryde's whale and sei whales in their records. Bryde's whales have a very streamlined and sleek body shape. Most Bryde's whales have three prominent ridges on the rostrum (other rorquals generally have only one). 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. The flukes are broad with a relatively straight trailing edge. Bryde's whales often exhale underwater, then surface with little or no visible blow. Bryde's whales have a relatively simple, countershaded color pattern, and are dark gray dorsally and lighter ventrally. The 250-370 pairs of gray baleen plates have light gray fringes, which are relatively coarse. The longest plates reach about 40 cm.
Bryde's whales are most likely to be confused with sei whales, and less likely with Fin and Omura's whales. Careful attention to body size, dorsal fin shape and position, head shape, and color pattern will help to distinguish among the four. The three head ridges of Brycle's whales (sei and fin whales always appear to have just one medial ridge), and much larger size and symmetrical head coloration of fin whales will help make them distinguishable from Bryde's whale. Also, pay particular attention to the tip of the upper jaw, which is generally bquite flat in Bryde's whales this species are not known to make extensive north/south migrations, as do other species of baleen whale, although short migrations have been documented in some areas. 
Their blow is columnar or bushy, about 10–13 feet 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. They usually appear individually or in pairs, and occasionally in loose aggregations of up to twenty animals around feeding areas. Not much is known of the ecology of the Bryde's whale. Although generally seen alone or in pairs, Bryde's whales do aggregate into groups of up to 10-20 on feeding grounds. 
Bryde's whales are primarily schooling-fish eaters (common prey species include pilchard, anchovy, sardine, mackerel, and herring), but they also take squid, krill, pelagic red crabs, and other invertebrates. They are very active lunge feeders, often changing direction abruptly when going after mobile fish prey. They have also been observed using bubble nets to corral prey. These whales opportunistically feed on plankton, and crustaceans, as well as schooling fish (e.g., anchovy, herring, sardine, mackerel, and pilchard). Bryde's whale use several feeding methods, including skimming the surface, lunging, and bubble nets.
Bryde's whales were never hunted as heavily as their larger cousins, the blue, fin, and sei whales. Fewer than 8,000 were killed in the Southern Hemisphere in the 1900s. Due to this fact, most populations of the Bryde's whale have not been seriously depleted. In recent years, some Bryde's whales have been taken by the Japanese in the North Pacific, and low numbers of small whales have been killed by artisanal whalers from villages in Indonesia. There are no estimates of global abundance. The species is not considered to be endangered or threatened, and at least the western North Pacific stock is thought to be increasing. Habitat modification and noise disturbance may be additional human-caused threats.

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