Sei Whale

Open encyclopedia reference

The sei whale ( SAY; Balaenoptera borealis) is a baleen whale. It is one of ten rorqual species, and the third-largest member after the blue and fin whales. It can grow to 19.5 m (64 ft) in length and weigh as much as 28 t (28 long tons; 31 short tons). Two subspecies are recognized: B. b. borealis and B. b. schlegelii. The whale's ventral surface has sporadic markings ranging from light grey to white, and its body is usually dark steel grey in colour. It is among the fastest of all cetaceans, and can reach speeds of up to 50–55 km/h (31–34 mph) over short distances. 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, subpolar waters in summer to temperate, subtropical waters in winter with a lifespan of 70 years. It is a filter feeder, with its diet consisting primarily of copepods, krill, and other zooplankton.

Wikipedia contributors, Sei whale; see linked history · CC BY-SA 4.0 . Plain-text lead excerpt, at most 180 words; no infobox or later sections Retrieved 2026-10-05T01:43:02.496498+00:00. This reference remains separate from the taxonomic record.

Identity & source status

Scientific name

Balaenoptera borealis Lesson, 1828

Name authority

Lesson, 1828

Common name

Sei Whale

Rank

species

Accepted status

accepted

Kingdom

Animalia

Phylum

Chordata

Class

Mammalia

Order

Cetacea

Family

Balaenopteridae

Genus

Balaenoptera

Extinction status

Recorded extant

Classification family tree

Nested taxonomic groups from the source. This is not a direct-ancestor chain, a dated evolutionary tree or a phylogenetic reconstruction.

1. domainEukaryota (Chatton, 1925) Whittaker & Margulis, 1978
2. kingdomAnimalia
3. phylumChordata
4. subphylumVertebrata
5. infraphylumGnathostomata
6. parvphylumOsteichthyes
7. megaclassTetrapoda
8. classMammalia Linnaeus, 1758
9. subclassTheria Parker & Haswell, 1897
10. infraclassEutheria Gill, 1872
11. orderCetacea Brisson, 1762
12. suborderMysticeti Flower, 1864
13. familyBalaenopteridae Gray, 1864
14. genusBalaenoptera Lacépède, 1804
15. speciesBalaenoptera borealis Lesson, 1828

Close classified relatives

These entries share the source’s genus, Balaenoptera. They are not necessarily the closest relatives established by molecular evidence.

Browse 8 records assigned to Balaenopteridae.

Documented distribution

Source distribution statements, not a complete range map. A listed locality is not necessarily a place of origin.

Source literature & publication evidence

References attached to this source record, including nomenclatural citations where supplied. This is a selected bibliography; abbreviated citations remain in the source’s form.

1. https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=180526 Source fields: Taxon.tsv dwc:namePublishedIn, Taxon.tsv dcterms:references

Origins, evidence & remaining research

Name authority and publication references document nomenclature where the source supplies it. They do not establish evolutionary origins or the earliest fossil occurrence.

Specimen-level evidence, morphology, ecological research, phylogenetic studies, a comprehensive bibliography and a located literary passage have not yet been compiled for this record.

Dataset citation & attribution

This exact taxon in ChecklistBank · Catalogue of Life 2026-09-11

Catalogue of Life 2026-09-11; dataset 316321; doi:10.48580/dgz5n. https://creativecommons.org/licenses/by/4.0/ . Retrieved 5 October 2026.

Stable key: col:KF8M. Classification follows source parent identifiers. English common names may vary by region.