| Home: Special status species: Sei whale: Natural history |
SPECIAL STATUS SPECIES: SEI WHALE (Balaenoptera borealis)
NATURAL HISTORY |
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| General |
| Taxonomy: |
Suborder Mysticeti
(Baleen Whales); Family Balaenopteridae (Rorquals).
|
| Appearance: |
Sei whales have a
large, sleek body. Females are slightly larger than
males; adult females average 15 m (50 ft) and 40,000
kg (88,000 lb) and adult males average 14 m (46 ft).
The dorsal fin is large, prominent and often falcate.
A single longitudinal ridge runs down the midline
of the top of the head. They have 30 to 60 ventral
pleats that extend from the throat along the upper
belly. The body is dark gray above and white or cream-colored
below. Oval scars often cover the body, probably caused
by cookie-cutter sharks, lampreys and other ectoparasites.
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| Feeding Behavior |
| Overview: |
This species feeds alone or in
small groups, but large loose aggregations may occur
in prime foraging areas. Often observed feeding near
the surface. Sei whales eat a much wider variety of
prey than the other large rorquals found off California. |
| Prey Items: |
Schooling fish (Northern
anchovy, Pacific saury, juvenile rockfish, Pacific
sardine, jack mackerel), krill, copepods, and squid |
| Method of
Capture: |
Sei whales
feed on schools of fish, krill, and squid by lunging
into the schools
and gulping large quantities of water and prey to
be filtered through the baleen. Feeds on smaller
zooplankton
by skimming, which entails swimming with the mouth
open and constantly filtering water through the
baleen
plates. |
|
| Reproduction |
|
| Overview: |
No distinct breeding or calving
grounds have been identified and little is known about
the mating system. |
| Time to Maturity: |
Mature at a mean age
of 10 years; males at 12.8 m (42 ft); females at 13.3
m (43.5 ft)7
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| Longevity: |
Up to 60 years3 |
| Breeding
Season: |
Calving
occurs from September to March, with a peak in November;7
breeding probably occurs in the winter |
| Frequency
of Breeding: |
Females usually give birth every
2-3 years7 |
| Gestation
Period: |
Approximately 12-13
months7
|
| Number of
Offspring per Pregnancy: |
One calf |
| Parental
Care: |
Maternal; female nurses calf
for ~9 months7 |
| Mating
System: |
Probably polygamous
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