Sei Whale

The sei whale Balaenoptera borealis, is a baleen whale, the fourth-largest rorqual after the blue whale, the fin whale and the humpback whale. It inhabits most oceans and adjoining seas, and prefers deep offshore waters. It avoids polar and tropical waters and semi-enclosed bodies of water. The sei whale migrates annually from cool and subpolar waters in summer to winter in temperate and subtropical waters.

Reaching 19.5 metres (64 ft) long and weighing as much as 28 tonnes (28 long tons; 31 short tons), the sei whale daily consumes an average of 900 kilograms (2,000 lb) of food, primarily copepods, krill, and other zooplankton. It is among the fastest of all cetaceans, and can reach speeds of up to 50 kilometres per hour (31 mph) (27 knots) over short distances. The whale's name comes from the Norwegian word for pollock, a fish that appears off the coast of Norway at the same time of the year as the sei whale.

Sei Whale
  • Size

    The sei whale is the fourth-largest balaenopterid, after the blue whale (up to 180 tonnes, 200 tons) and the fin whale (up to 70 tonnes, 77 tons) and the humpback whale (upto 40 tonnes, 44.5 tons).

    Adult Sei Whales reach lengths of about 40-64 ft (12-19,5 m) and weigh 100,000 lbs (45,000 kg). Females may be slightly longer than males.

    At birth, a calf typically measures 4.4-4.5 m (14.4-14.7 ft) in length.

  • Feeding

    This rorqual is a filter feeder, using its baleen plates to obtain its food by opening its mouth, engulfing or skimming large amounts of the water containing the food, then straining the water out through the baleen, trapping any food items inside its mouth. The sei whale feeds near the surface of the ocean, swimming on its side through swarms of prey to obtain its average of about 900 kilograms (2,000 lb) of food each day. For an animal of its size, for the most part, its preferred foods lie unusually relatively low in the food chain, including zooplankton and small fish.

  • Life History

    Sei whales become sexually mature at 6-12 years of age when they reach about 45 ft (13 m) in length, and generally mate and give birth during the winter in lower latitudes. Females breed every 2-3 years, with a gestation period of 11-13 months. Females give birth to a single calf that is about 15 ft (4.6 m) long and weighs about 1,500 lbs (680 kg). Calves are usually nursed for 6-9 months before being weaned on the preferred feeding grounds. Sei whales have an estimated lifespan of 50-70 years.

  • Behavior

    Sei whales usually travel alone or in pods of up to six individuals.Larger groups may assemble at particularly abundant feeding grounds. Very little is known about their social structure. Unlike the fin whale, the sei whale tends not to rise high out of the water as it dives, usually just sinking below the surface. The blowholes and dorsal fin are often exposed above the water surface almost simultaneously. The whale almost never lifts its flukes above the surface, and are generally less active on water surfaces than close related Bryde's whales.