Sei whale
Sei whale
| | Sei (pronounced 'say') whales (Balaenoptera borealis) are the third largest of the baleen whales, reaching about 16 metres and 25 tonnes.
The most 'northerly' of the Antarctic baleen whales, sei whales are often found to the north of the Polar Front in summer, as far as north Tasmania; but they are seen occasionally feeding in the southern most navigable waters of Antarctica.
Sei whales are the only member of the rorqual family (the 'groove throated' whales including the humpback and blue whales) that feed on minute copepod crustaceans, rather than on larger krill. Their feeding method is different too: rather than 'gulping' their food in large mouthfuls, they 'skim' it by swimming along with their mouths open.
Sei whales are possibly the fastest swimming baleen whales, and have been clocked at 25 km/h for an hour when chased by whalers.
After the larger blue and fin whales were decimated by Antarctic whaling in the 1950s and 1960s, sei whales became the target, and were not protected until 1978. Their numbers were severely reduced.
Sei whale winter breeding areas are unknown, but probably lie somewhere in deep tropical waters; however some individuals have been seen around Tasmania in winter, possibly non-breeding whales.
After a pregnancy of 11.5 months, a single calf is born in winter, and is suckled for about 7 months before becoming independent of its mother.
Sei whales, like other baleen whales, do not seem to form lasting family groups (unlike many toothed whales) and very little is known of their social lives; they are usually seen in groups of less than five.
Sei whales rarely dive deeper than 300m, or for more than 20 minutes, as their prey is usually found quite close to the surface.
While Sei whales are often pictured as uniformly coloured, they often have very subtle, beautiful swirling markings on their skin.
Related links
Taxonomic information on Sei whales
Australian Government information on whales
Australian Antarctic Science (AAS) projects relating to the whales
Australian Antarctic publications relating to whales
Selected publications relating to whales
Cooke, J.G. and de la Mare, W.K. (1994). Some aspects of the estimation and modelling of baleen whale sustainable yields. Reports of the International Whaling Commission Serial 44 451-457
Fordyce, R.E. and Quilty, P.G. (1994). Pliocene whales and dolphins (Cetacea) from the Vestfold Hills. Records of the South Australian Museum Serial 27 219
Nicol, S. (1991). Whale food for people: tinned, frozen or preserved? Australian Geographic Serial 17-18.
Parker, D.A.A. (1978). Observations of whales on ANARE voyages between Australia and Antarctica. Australian Wildlife Research Serial 5 25-39.
Thiele, D. and Gill, P.C. Preliminary results of a Southern Ocean cetacean sightings survey in Areas IV and V. Paper SC/48/SH22 presented to the IWC Scientific Committee, June 1996 (unpublished). 24pp
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