Animal Info - Blue Whale

(Other Names: Baleine Bleue, Baleine d'Ostende, Baleinoptère Bleue, Ballena Azul, Rorcual Azul, Rorqual Bleu, Rorqual de Sibbold, Rorqual à Ventre Cannelé, Sibbald's Rorqual, Sulphur Bottom Whale)

Balaenoptera musculus

Status: Endangered


Contents

1. Profile (Picture)
2. Tidbits
3. Status and Trends (IUCN Status, Oceans and Seas Where Currently Found, Population Estimates, History of Distribution, Threats and Reasons for Decline)
4. Data on Biology and Ecology (Size and Weight, Habitat, Age to Maturity, Gestation Period, Birth Season, Birth Rate, Early Development, Dispersal, Maximum Age, Diet, Behavior, Social Organization, Age and Gender Distribution, Mortality and Survival)
5. References


Profile

Pictures: Blue Whale #1 (3 Kb JPEG) (Mammal Soc. Britain); Blue Whale #2 (16 Kb JPEG) (Univ. Wash.); Blue Whale #3 (89 Kb GIF) (NOAA Yr. of the Ocean); Blue Whale #4 (64 Kb JPEG) (Univ. Texas) 

The blue whale is the largest animal that has ever lived on earth. It can weigh up to 136,400 kg (300,000 lb) and grow as long as 34 m (110'). It has a slim outline, especially in the winter, although it fattens in the summer. The tiny dorsal fin is set well to the rear of the body. 55 - 68 flexible throat grooves run along half the body length. Its coloration is mainly pale blue-gray. 

The blue whale occurs mostly in cold and temperate waters. It prefers deeper ocean waters as opposed to coastal waters. Its diet consists almost entirely of shrimplike crustaceans known as krill, which it eats during the summer feeding season. During the other 8 months of the year it apparently doesn't eat anything, living off of stored fat. 

The blue whale usually feeds at depths of less than 100 m (330'). A dive usually lasts 10 - 20 minutes. When making a deep dive, the whale "headstands," exposing its wide tail flukes, then descends steeply. On returning to the surface, the whale releases a "blow," about 9 m (30‘) high, consisting of warm, humid air from the lungs, mucus, and ocean water. Blue whales have very deep voices and can vocalize at a volume of greater than 180 decibels, the loudest sound of any animal. Blue whales are usually solitary or in pairs ( mother-calf pairs or two adults), although they may gather in loose groups to feed. 

The blue whale is found in all major oceans of the world. Its populations have been severely depleted throughout its range due to commercial whaling, which ceased in 1964. There have been reports of increased sightings in some areas, but in other areas the number of blue whales remains low. 


Tidbits

*** The blue whale is the largest creature that has ever existed on earth. It is bigger than 25 elephants; bigger than a Brontosaurus and a Tyrannosaurus rex combined. A blue whale calf is about 7 m (23') long at birth.

*** The sounds a blue whale makes can travel thousands of miles in deep water, leading to speculation that the whales may be able to communicate across oceans. 


Status and Trends

IUCN Status:

Oceans and Seas Where the Blue Whale Is Currently Found:

2006: Occurs in the Arctic Sea, Atlantic Ocean (Antarctic, eastern central, northeast, northwest, southeast, southwest, western central), Indian Ocean (Antarctic, eastern, western), and Pacific Ocean (Antarctic, eastern central, northeast, northwest, southeast, southwest, western central). (IUCN 2006)

Countries Where the Blue Whale Is Currently Found:

2006: Occurs in Argentina, Australia, Bangladesh, Canada, Cape Verde, Chile, Ecuador, Iceland, India, Indonesia, Japan, Kenya, Democratic People's Republic of Korea, Republic of Korea, Malaysia, Mexico, Myanmar, Namibia, New Zealand, Nicaragua, Norway, Pakistan, Panama, Peru, Russia, South Africa, Spain, Sri Lanka, Tanzania, United Kingdom, United States, and Uruguay (IUCN 2006).

Population Estimates:

History of Distribution:

The blue whale is found in all major oceans of the world. Its populations have been severely depleted throughout its range due to commercial whaling, which ceased in 1964. There have been reports of increased sightings in some areas (for example, in 1988, blue whales were seen off of Jan Mayen Island, 1000 km (620 mi) west of Norway, for the first time in 30 years).  Furthermore, there are trends of increase around Iceland and offshore of the west coast of the USA.  On the other hand, the number of blue whales in the Antarctic remains extremely low; there is a complete absence of blue whales off southern Japan, and blue whales are apparently rare in the Gulf of Alaska and the southern Bering Sea, where they were once abundant.  (Klinowska 1991, Reeves et al. 2003)

Distribution Map (10 Kb GIF) (Mammal Soc. Britain)

Threats and Reasons for Decline:

Overfishing by the whaling industry was the cause of the blue whale's decline.


Data on Biology and Ecology

Size and Weight:

Typical weight of a blue whale: 108,000 kg (238,000 lb); up to 136,000 kg (300,000 lb). 
Length - up to 34 m (110'); average (Antarctic stock): 27 m (89') (females); 25 m (82') (males).

Habitat:

The blue whale is found mostly in cold and temperate waters. It prefers deeper ocean waters to coastal waters.

The blue whale occurs in the Icelandic & Celtic Marine Ecosystems, Southern Caribbean Sea, and Sea of Cortez Global 200 Ecoregions. (Olson & Dinerstein 1998, Olson & Dinerstein 1999)

Age to Maturity:

In the Northern Hemisphere, females reach sexual maturity in 5 years at lengths of 21 - 23 m (69 - 75'). Males mature in slightly less time at just under five years and at slightly shorter lengths of 20 - 21 m (66 - 69'). (Wilson & Ruff 1999)

Length at maturity in the Southern Hemisphere for females is 23 - 24 m (75 - 79').

Gestation Period:

10 - 11 months.

Birth Season:

Calves are born in late fall and winter. 

Birth Rate:

Usually one calf is born. Twins have been reported on rare occasions. The time between births is usually 2 - 3 years, although there is some indication that the current interval is shorter than before the populations were decimated by whaling, possibly as a density-dependent mechanism to increase the growth rate of the populations.

Early Development:

A calf is weaned at about 6 - 8 months, when it is about 16 m (52') long.

Dispersal:

After it is weaned, a calf leaves its mother to follow the normal migration pattern independently. 

Maximum Age:

Maximum age estimates for blue whales range up to 80 - 90 years (Wilson & Ruff 1999).

Diet:

Blue whales feed almost exclusively on shrimplike crustaceans known as "krill".  A blue whale may consume up to 5.5 - 6.4 metric tons (6 - 7 tons) of food per day during the summer feeding season. During the other 8 months of the year, it apparently doesn't eat anything, living off of stored fat.

The blue whale has long, flexible throat grooves. It feeds by using these groves to expand its throat and drawing in water laden with prey, then forcing the water out through its baleen plates. These plates filter out the prey organisms, which the whale then swallows.

Behavior:

Migration: In both the Northern and Southern Hemispheres, in the summer the blue whale populations migrate towards the pole of their respective hemisphere into cooler waters to feed. They migrate back towards the equator, into warmer waters, in the winter to breed. Because the seasons are opposite in the Northern and Southern Hemispheres, the net result of these movements is that the Northern Hemisphere and Southern Hemisphere stocks of blue whales do not mix.

Swimming: The blue whale ranks among the fastest of the whales, with feeding speeds of 2 - 6.5 km/h (1.2 - 4 mi/h) and cruising speeds of 5 - 33 km/h (3 - 20 mi/h). When chased, it can reach speeds as high as 48 km/h (30 mi/h).

Diving:  The blue whale usually feeds at depths of less than 100 m (330'), up to 200 m (660'). A dive usually lasts 10 - 20 minutes. When making a deep dive, the whale "headstands," exposing its wide tail flukes, then descends steeply. Its long, narrow flippers play no part in propulsion - the thrust comes from the powerful back muscles that swish the rear body and flukes up and down. On returning to the surface, the whale releases a "blow," about 9 m (30‘) high, consisting of warm, humid air from the lungs, mucus, and ocean water. (Burnie & Wilson 2001)

Sounds:  The blue whale makes sounds that can be characterized as grunts, hums, moans, and clicks. Blue whales have very deep voices, vocalizing at frequencies as low as 14 Hz - below the range of human hearing - at a volume of greater than 180 decibels, the loudest sound of any animal. (Wilson & Ruff 1999, Burnie & Wilson 2001)

Social Organization:

Blue whales are usually solitary or in pairs (mother-calf pairs or two adults), although they may gather in loose groups to feed. By determining gender through DNA analysis, one study determined that paired adult blue whales are usually a male and a female. Often, the same two whales will be seen together over a long period of time. Some males, however, have paired with different females at different times. (Powell 1998, Burnie & Wilson 2001)

Age and Gender Distribution:

The male:female ratio at birth and throughout most of the life cycle is about 1:1.

Mortality and Survival:

An estimate of the recent rate of increase of blue whale abundance in some regions of the North Atlantic yielded a result of 5.2% per year (Klinowska 1991).


References

Arkive, Bonner 1989, Burnie & Wilson 2001, Curry-Lindahl 1972, IUCN 1966, IUCN 1994, IUCN 1996, IUCN 2000, IUCN 2003a, IUCN 2004, IUCN 2006, Kemf & Phillips 1994, Klinowska 1991, Macdonald 1984, Mammal Soc. Britain, NOAA Yr. of the Ocean, Nowak & Paradiso 1983, Olson & Dinerstein 1998, Olson & Dinerstein 1999, Oryx 1964a, Oryx 1989i, Powell 1998, Reeves et al. 2003, Univ. Texas, Univ. Wash., Watson 1996, Wilson & Ruff 1999


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Last modified: June 5, 2006;

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