| Home: Special status species: Blue whale : Natural history |
| SPECIAL STATUS SPECIES: BLUE WHALE (Balaenoptera musculus) NATURAL HISTORY |
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| General |
| Taxonomy: |
Suborder Mysticeti (Baleen Whales); Family Balaenophteridae (Rorquals). Three subspecies are currently accepted26: B. m. musculus is the subspecies in the North Pacific and North Atlantic.
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| Appearance: |
Blue whales are the largest animals on the earth. The largest blue whales, reaching approximately 100 feet, live in the southern hemisphere. In the North Pacific adults can reach 27 m (89 ft) and 100,000-120,000 kg (220,500 - 264,500 lb); females are larger than males.1 Their body is long, slender and a mottled, blue-gray color. The top of the head is flat in profile with a large splashguard in front of two blowholes. They have 55 to 68 ventral pleats that extend along the throat to the belly. A very small dorsal fin is set far back on the body. |
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| Feeding Behavior |
| Overview: |
Feeds alone or in small groups, but groups do not appear to feed cooperatively. Large loose aggregations may occur in prime foraging areas. Blue whales are estimated to eat from 2-4 tons (1,800-3,600 kg) of food per day. Both sexes may make short–duration vocalizations during feeding. One study of tagged blue whales found that foraging dives averaged 140 m and 7.8 min, while the deepest dive was approximately 200 m and the longest dive was 15 min.17 Other tagging studies have recorded dives to 300 m. 3 |
| Prey Items: |
Feeds almost exclusively on krill; primarily on Euphausia pacifica and Thysanoessa spinifera off California, Oregon, and Washington, with Nyctiphanes simplex becoming part of the diet to the south. |
| Method of
Capture: |
Feeds by lunging into swarms of krill and gulping large quantities of water and prey. Large volumes of water and food can be taken into the mouth because the pleated grooves in the throat expand. As the mouth closes water is expelled through the baleen plates, which trap the food on the inside near the tongue to be swallowed. |
Photo: Protected Resouces Division, Southwest Fisheries Science Center, La Jolla, California. http://swfsc.nmfs.noaa.gov/PRD/.
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| Reproduction |
| Overview: |
Male blue whales make an intense long-duration, low frequency call. Although the function of the call has not been determined, speculation includes communication over long distances or male mating displays. |
| Time to Maturity: |
5-15 years; females at a length of 21-23 m; males at a length of 20-21 m18 |
| Longevity: |
Probably to at least 70-80 years18 |
| Breeding
Season: |
Calving and mating occurs during the winter season1 |
| Frequency
of Breeding: |
Females usually give birth every 2-3 years1 |
| Gestation
Period: |
Approximately 10-12 months1 |
| Number of
Offspring per Pregnancy: |
One |
| Parental
Care: |
Maternal; female nurses calf for 6-7 months1 |
| Mating
System: |
Very little is known; probably polygamous. Males may compete with other males for access to females. |
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