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Balaenoptera musculusblue whale

By Tanya Dewey and David L. Fox

Ge­o­graphic Range

Blue whales are found in all oceans of the world, from the trop­ics to the drift ice of polar wa­ters. (Nowak, 1991; Wil­son and Ruff, 1999)

Habi­tat

Blue whales live in the open ocean. (Nowak, 1991; Wil­son and Ruff, 1999)

Phys­i­cal De­scrip­tion

Blue whales are slate to gray­ish blue and mot­tled with lighter spots, par­tic­u­larly on the back and shoul­ders. The un­der­sides often be­come cov­ered with mi­croor­gan­isms, giv­ing the belly a yel­low­ish tinge. Be­cause of this blue whales are some­times called "sul­phur­bot­toms". The dor­sal fin is short, only about 35 cm. The upper jaw is the widest in the genus, and the ros­trum is the bluntest. There are 50-90 throat grooves that ex­tend from the chin to just be­yond the navel.

Blue whales are the largest an­i­mals ever to exist on earth. Av­er­age head-body length in adult males is 25 m; in fe­males it is 27 m. The longest con­firmed spec­i­men was 33.5 m in length and the heav­i­est was 190,000 kg. (Nowak, 1991; Wil­son and Ruff, 1999)

  • Sexual Dimorphism
  • female larger
  • Range mass
    190000 (high) kg
    418502.20 (high) lb
  • Average mass
    190000 kg
    418502.20 lb
  • Range length
    33.5 (high) m
    109.91 (high) ft
  • Average length
    25-27 m
    ft

Re­pro­duc­tion

Very lit­tle is known about mat­ing in the large whale species.

The ges­ta­tion pe­riod is eleven or twelve months long, un­usu­ally short for an an­i­mal its size. Young are born in warm, low lat­i­tude wa­ters in the win­ter months after the adults re­turn from their high lat­i­tude feed­ing grounds. At birth the young are 7-8 m long. While nurs­ing, blue whales can gain up to 90 kg in body weight a day. Young are weaned after seven or eight months, usu­ally after at­tain­ing a length of 16 m. Sex­ual ma­tu­rity oc­curs at about 5 years old in fe­males, or at about 21 to 23 m in length and young are pro­duced every 2 or 3 years after that. Twins are rare but do occur oc­cas­sion­ally. Males ma­ture at 20 to 21 m, just under 5 years old. Longevity has been es­ti­mated to be as high as 110 years. (Nowak, 1991; Wil­son and Ruff, 1999)

  • Breeding interval
    Females give birth to young every 2 to 3 years.
  • Breeding season
    Breeding occurs during the winter months.
  • Average number of offspring
    1
  • Average number of offspring
    1
    AnAge
  • Range gestation period
    11 to 12 months
  • Range weaning age
    7 to 8 months
  • Range time to independence
    2 to 3 years
  • Average age at sexual or reproductive maturity (female)
    5 years
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    1827 days
    AnAge
  • Average age at sexual or reproductive maturity (male)
    5 years
  • Average age at sexual or reproductive maturity (male)
    Sex: male
    1827 days
    AnAge

Blue whale young are cared for ex­ten­sively by their mother. Male blue whales do not con­tribute parental care. (Nowak, 1991; Wil­son and Ruff, 1999)

  • Parental Investment
  • no parental involvement
  • precocial
  • pre-fertilization
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • provisioning
      • female
    • protecting
      • female

Lifes­pan/Longevity

Longevity in blue whales, and other large cetaceans, is es­ti­mated by count­ing the num­ber of ovar­ian scars in sex­u­ally ma­ture fe­males, changes in the col­oration of eye lenses, and count­ing the num­ber of ridges on baleen plates. Age es­ti­mates of blue whales sug­gest a lifes­pan of 80 to 90 years. (Wil­son and Ruff, 1999)

  • Average lifespan
    Status: wild
    80-90 years
  • Typical lifespan
    Status: wild
    80 to 90 years

Be­hav­ior

Most pop­u­la­tions of blue whales are mi­gra­tory, though some an­i­mals do not mi­grate. Mi­gra­tors typ­i­cally spend the win­ter in low lat­i­tude wa­ters, move to­wards the poles dur­ing the spring, feed in high lat­i­tude wa­ters dur­ing the sum­mer and head back to­ward the equa­tor dur­ing the fall. There are north­ern and south­ern ocean pop­u­la­tions that re­main dis­tinct. Nor­mal swim­ming speed is around 22 km/hr, but blue whales can make 48 km/hr if alarmed. Feed­ing is usu­ally at depths less than 100 m; har­pooned an­i­mals have dived as deep as 500 m. Nor­mal dives last from 10-20 min­utes and are sep­a­rated by 8-15 blows. The spout of blue whales can reach al­most 10 m. Ag­gre­ga­tions of up to 60 an­i­mals have been re­ported, but soli­tary an­i­mals or pods of two or three are more com­mon. (Wil­son and Ruff, 1999)

Com­mu­ni­ca­tion and Per­cep­tion

Blue whales have the low­est voices of any whale, vo­cal­iz­ing as low as 14 Hz at vol­umes up to 200 deci­bels. Sounds at this fre­quency and in­ten­sity can travel for thou­sands of miles in the deep ocean. These sounds may be used to com­mu­ni­cate with other whales. Low fre­quency pulses may be used to nav­i­gate by cre­at­ing a sonic image of dis­tant oceanic fea­tures.

Lit­tle is known about in­traspe­cific com­mu­ni­ca­tion in these whales. Vi­sion and smell are lim­ited, but hear­ing is sen­si­tive. (Wil­son and Ruff, 1999)

Food Habits

The diet of blue whales is prin­ci­pally krill. In south­ern wa­ters the main species eaten is Eu­phau­sia su­perba, a small (less than 7 cm) plank­tonic crus­tacean that is tremen­dously abun­dant. In north­ern wa­ters the main species are Thysa­noessa in­er­mis and Meganyc­tiphanes norvegica, though other plank­tonic species and small fish are also eaten. Adult whales can in­gest 3 to 4 tons of krill per day.

  • Primary Diet
  • carnivore
    • eats non-insect arthropods

Pre­da­tion

Blue whales, by virtue of their ex­treme size, have vir­tu­ally no nat­ural preda­tors. They were hunted by hu­mans ex­ten­sively in the 20th cen­tury, al­most to ex­tinc­tion. Blue whale calves may be vul­ner­a­ble to pre­da­tion by orcas and large sharks.

Ecosys­tem Roles

Blue whales, and other large baleen whales, are im­por­tant preda­tors of krill.

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

Blue whales were for­merly heav­ily hunted for blub­ber and oil. Be­cause of the im­men­sity of blue whales, only sperm whales ap­proached them in eco­nomic im­por­tance. A sin­gle blue whale could yield 70 or 80 bar­rels of oil. Baleen was also an im­por­tant whale prod­uct, val­ued for its plas­tic like prop­er­ties that were ap­plied in a wide va­ri­ety of prod­ucts.

Blue whales, and other large whales, have im­por­tant eco­tourism value.

  • Positive Impacts
  • body parts are source of valuable material
  • ecotourism

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

There are no neg­a­tive im­pacts of blue whales on hu­mans.

Con­ser­va­tion Sta­tus

Blue whales were not ini­tially among the most heav­ily hunted species due to their size, speed, and re­mote habi­tat. Tech­no­log­i­cal ad­vances from 1860-1920, how­ever, al­lowed whalers to pur­sue the species. The es­ti­mated total kill of blue whales in the 20th cen­tury was 350,000 an­i­mals. By the 1960's, blue whales were on the edge of ex­tinc­tion. De­spite the op­po­si­tion of the whal­ing in­dus­try, blue whales gained pro­tec­tion after the 1965/66 whal­ing sea­son. Es­ti­mates of the re­main­ing pop­u­la­tion range from 2,000 to 6,000 in­di­vid­u­als and it is not yet clear that the blue whale will es­cape ex­tinc­tion. South­ern hemi­sphere pop­u­la­tions have been sur­veyed ex­ten­sively and are es­ti­mated at 400 to 1,400 an­i­mals. North­ern hemi­sphere pop­u­la­tions are es­ti­mated at about 5,000 in­di­vid­u­als but the sci­en­tific rigor of these sur­veys has been crit­i­cized.

Con­trib­u­tors

Tanya Dewey (au­thor, ed­i­tor), An­i­mal Di­ver­sity Web.

David L. Fox (au­thor), Uni­ver­sity of Michi­gan-Ann Arbor.

Glossary

Arctic Ocean

the body of water between Europe, Asia, and North America which occurs mostly north of the Arctic circle.

Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

ecotourism

humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

filter-feeding

a method of feeding where small food particles are filtered from the surrounding water by various mechanisms. Used mainly by aquatic invertebrates, especially plankton, but also by baleen whales.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

migratory

makes seasonal movements between breeding and wintering grounds

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

pelagic

An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).

polar

the regions of the earth that surround the north and south poles, from the north pole to 60 degrees north and from the south pole to 60 degrees south.

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

young precocial

young are relatively well-developed when born

zooplankton

animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)

Ref­er­ences

Nowak, R. 1991. Walker's Mam­mals of the World. Bal­ti­more, Mary­land, USA: The Johns Hop­kins Uni­ver­sity Press.

Tin­ker, S. 1988. Whales of the World. Lei­den, The Nether­lands: E.J. Brill.

Wil­son, D., S. Ruff. 1999. The Smith­son­ian Book of North Amer­i­can Mam­mals. Wash­ing­ton: Smith­son­ian In­sti­tu­tion Press.

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Classification

  • Kingdom Animalia animals
  • Phylum Chordata chordates
  • Subphylum Vertebrata vertebrates
  • Class Mammalia mammals
  • Order Cetacea dolphins, porpoises, and whales
  • Family Balaenopteridae rorquals
  • Genus Balaenoptera rorquals
  • Species Balaenoptera musculus blue whale