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Smithsonian National Museum of Natural History, North American Mammals

  Cetacea · Balaenopteridae · Balaenoptera borealis

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Balaenoptera borealis

Sei Whale

Order: Cetacea
Family: Balaenopteridae

Image of Balaenoptera borealis
Balaenoptera borealis - insets: view of head from top, spray pattern
Click to enlarge this image. (41 kb)

Conservation Status: Endangered.

Unlike other rorquals, Sei whales have a dolphin-like dorsal fin. They are also unusual in using two different methods to fill their mouths with water during feeding - they both gulp and skim-feed. During feeding, these whales can be found in large numbers, probably around concentrations of copepods, a crustacean they favor. Otherwise, they occur in smaller groups of six or less. The sei whale is endangered, and it has been protected by the International Whaling Commission since the mid-1980s. The common name, pronounced "sigh,"  comes from the Norwegian word for codfish, which sei whales are known to eat. "Rorqual" is also a word of Scandinavian origin, meaning "tubed," and refers to the grooved, expandable throats of the six species of whales in the family Balaenopteridae.


Range: 14-18.6 m


Range: 8,500-11,300 kg males; 8,600-15,000 kg females


Lesson, René Primevère, 1828. Histoire naturelle générale et particulière des Mammifères et des Oiseaux découverts depuis 1788 jusqu'à nos jours, Baudoin Frères, Paris, 1:342.


Mammal Species of the World (opens in a new window).

Distribution of Balaenoptera borealis

Image of Balaenoptera borealis
Balaenoptera borealis baleen, right (with B. Edeni baleen)
Click to enlarge this image. (81kb)

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