Common Name: Sei Whale
whales belong to the Mammalian Order Cetacea, in the suborder
Mysticeti. All baleen whales belong to the suborder Mysticeti,
which is Latin for "mustached whales". The sei whale belongs to the
rorqual family, Balaenopteridae. The word "rorqual" means "tube
whale or furrowed whale", referring to the pleats on the lower jaws
of rorquals. All rorquals have baleen, a dorsal fin and throat
grooves. Other members of this family include the humpback whale,
fin whale, and minke whale. The sei whale's scientific name is
Balaenoptera borealis. Its generic name, Balaenoptera,
means "winged whale", which refers to the sei whale's dorsal fin.
The sei whale's specific name, borealis, means "northern".
The common name "sei", pronounced "say". It is derived from seje,
the Norwegian word for pollock, a relative of the codfish that
composes part of the whale's diet. Historically, sei whales
returned to the Norwegian coast each year to feed on pollock swarms
feeding on plankton. Sei whales and Bryde's whales are very similar
in appearance. Upon closer inspection, sei whales have one ridge on
their head, while Bryde's whales have three ridges. Sei whales may
exceed 60ft in length and weigh 14-17 tons. Female sei whales are
usually larger than males of the same age.
whales are found in all oceans, but do not venture into polar
regions. Their major food sources, krill and copepods, live in all
regions. Sei whales living in northern waters occasionally feed on
small fish. As the whale opens its large mouth to gulp up the
krill, the pleats of its lower jaw expand to contain the large
volume of water. The whale then presses its tongue up against the
roof of its mouth, straining the water through its 640-760 baleen
plates. These 19 inch plates are composed of keratin, the same
substance of fingernails and hair. The ends of baleen are
brush-like, preventing the prey from escaping. The copepods remain
inside, and are consequently swallowed. While feeding on plankton,
the sei whale will strain water at the ocean surface.
sei whale leads a solitary life. However, small groups of 2-3
animals are also commonly observed. Large congregations of one
hundred or more whales have been witnessed. Such large groupings
usually surround a common resource. The migration of sei whales to
a location rich with prey is typical. They are very fast swimmers,
reaching speeds of more than 30 knots. Sei whales do not arch their
backs or raise their flukes to dive. Instead, they gracefully sink
beneath the ocean surface.
breeding location of this species is unknown. Gestation lasts about
12 months. Calves are 14-15ft in length, weighing 2,000lbs at
birth. They nurse for six months. Little is known about sei whale
breeding and calving. Sexual maturity is reached at ten years by
males and females.
Sei whales are slimmer
than blue whales and fin whales because they have less blubber.
Consequently, sei whales were not hunted until blue whale and fin
whale populations were depleted. Sei whale hunting began during the
1950's. Within two decades, the Antarctic population of sei whales
crashed. Since that crash, sei whales have been protected.
One-fifth of the original population exists today, numbering around
54,000. A moratorium on all whaling has been established, and the
greatest current threat to sei whales is ocean pollution.