Aquarium of the Pacific - Online Learning Center - Species Print Sheet
Conservation Status: Endangered - Protected
(Balaenoptera musculus)Cetaceans • Whales • Mammals • Marine
The blue whale is believed to be the largest animal that has ever lived on Earth. It is a member of the family, Balaenopteridae, the rorqual whales. These baleen whales have a dorsal fin and throat grooves, or pleats. The name “rorqual” is derived from a Norwegian word, “rockval”, that means furrow, referring to the throat grooves.
There are three “true” whale subspecies of Balaenoptera musculus. In addition some researchers believe there is a fourth, the pygmy blue whale, B. m. brevicauda while others think the pygmy is merely a small true blue whale. The populations are geographically separated and do not intermix. Most are migratory.
At the Aquarium
Our anatomically correct (88 ft) fiberglass model of a female blue whale is named Edie. The calf, a male, is called Edison. The blue whale is also featured in signage, Whales: A Journey with Giants (a large screen, multimedia presentation), and the interactive kiosk, Whales: Voices in the Sea. Blue whales are seen in the wild as part of the Aquarium’s whale watching adventures on our local Pacific Ocean waters.
Seasonal breeding, calving, and feeding distribution in the global ocean’s tropic, temperate, and drift-ice polar waters
The usual habitat of these whales is the open ocean and the edges of continental shelves except in polar regions where they follow retreating ice edges. At times they also frequent coastal and near island areas. In summer months they move about in cold water seeking foraging areas where there are large concentrations of krill. Most migrate to warm tropical and subtropical waters in winter months for calving and breeding. A large population formerly found in the Santa Barbara Channel off the California coast from June through September appears to be moving south recently. In 2007 they have been commonly seen in ocean waters near Long Beach, California (100 miles south of the Santa Barbara Channel).
Blue whales have a smooth, slender, streamlined, and somewhat tapered body that begins with a pointed snout, and ends in broad triangular flukes that have a median notch and slightly concave or straight trailing edges. Their stubby and “tiny” (for an animal this size) dorsal fin is located three-quarters of the way along the back of their body. Its shape can be rounded, falcate (curved), or triangular. The rostrum of these whales is very flat, broad, and almost U-shaped. There is usually a single ridge that extends from the tip of the snout to just forward of the two blowholes. The blowholes are contained in a large raised splashguard. The slender pointed flippers are short for the body size. There are 55-68 throat grooves, or pleats, along the sides and ventrally that extend from the lower jaw to near or just beyond the navel.
Their baleen consists of 260 to 400 black, coarse, broad, overlapping plates hanging from each side of the upper jaw. The fringed plates taper from 51 cm (20 in) at the front to 102 cm (40 in) in length at the rear, the longest of the rorqual whales.
Blue whales are basically blue-gray in color, appearing aquamarine when under water. However, their true color varies among individuals from a uniform dark slate gray with little whitish mottling to a very light blue with extensive mottling. It is these mottling patterns, their unique fingerprints, which have formed the basis for photo identification of individual blue whales just as saddle and eye patches of killer whales and the black and white pigmentation of the underside of humpback flukes are used. The ventral side of their body is usually pale blue-gray or whitish, however, in whales that forage in cold polar waters it is often a yellowish color due to an accumulation of microscopic diatoms (one-cell algae). This coloration caused whalers to call blue whales “sulfur-bottoms”. The tips of their flukes can be lighter than the rest of the flukes.
These whales are 24-30 m (78-100 ft) long and weigh 72,000-136,000 kg (160,000-300,000 lbs). About 12% of the weight is blubber. Males are usually 1.5-3 m (5-10 ft) shorter than females. Southern blue whales are about 3.5 m (11 ft) larger than northern, a difference believed to be the result of the more abundant supply of krill in the Antarctic Ocean. The dorsal fin is about 30 cm (11.8 in) in height, flippers, 2.4 m (8 ft), and flukes, 7.6 m (25 ft).
Diet and Feeding
While blue whales may occasionally feed on pelagic crabs and small fishes, their diet is almost exclusively euphausiid shrimps commonly called krill. They are the most selective feeders of the baleen whales, consuming only certain species of krill and not others. (Krill preferences are determined by analyzing fecal samples.) The krill aggregate, move, and disperse from area to area and how these whales know where the swarms of krill are and when is still unknown. Some researchers believe they use sound to track them.
Blue whales usually feed at depths less than 100 m (328 ft) and no more than 152 m (500 ft). They lunge at dense clouds or patches of krill, expanding their throat grooves to take in as much as 64,252 l (17,000 gal) of food and water in a single mouthful. The water pressure causes their throat pleats to expand. They then partially close their mouth, exposing a fringe of comb-like baleen around the opening and use their tongue to force the water out of the baleen sieve, leaving the krill trapped in the fringes of the baleen plates to be swallowed. Blue whales need to take in 1.5 million calories a day to meet their energy requirements. Adults do this by consuming about 40 million krill a day or 3499 kg (7715 lb).
Neither actual mating of blue whales nor birth of a calf have been observed in modern times, and the breeding grounds for some populations are still unknown. Sexual maturity is believed to be reached between five and ten years of age when females are about 24 m (79 ft) long and males, 23 m (75 ft). Recent acoustical studies indicate that males may vocalize to attract females by using a very low frequency call referred to as the “A” call. (The frequency or hertz is so low that the human ear cannot hear it). Females do not seem to make this particular call. It has been noted that when pairs are observed, the whale in the lead is usually a female with a male trailing behind who becomes defensive if another whale approaches.
Most blue whales migrate from their colder water feeding grounds to warmer water latitudes to mate and calve. There are some, however, that may remain year round in colder latitudes depending on ice formation. In the Northern Hemisphere the migration occurs in the boreal winter approximately November–March, and in the Southern Hemisphere’s austral winter, June-September.
The gestation period is about 11 months, considered short for an animal the size of the blue whale. At birth the calf is 7-8 m (23-26 ft) long and weighs about 2500 kg (5500 lb) but that soon changes as it nurses on 397 l (105 gal) milk per day that is about 50 percent butterfat. Its growth is rapid as it gains about 90 kg (198 lb) per day or 3.7 kg (8.2 lb) per hour. When several months old it begins to both nurse and start to eat krill. It is weaned at seven to eight months of age at which time it is about 16 m (52 ft) long and weighs 20,900 kg (68,123 lb). Female blue whales are very good mothers. They give birth every two to three years.
The blows of blue whales are spectacular. The tall, straight column, 6-12 m (19.7-39 ft) high and about 6.7-7.6 m (22-25 ft) wide can be seen and heard as far as 6.4 km (4 mi) away. They usually blow in a relaxed fashion 8-15 times at 10-20 second intervals and then dive for 10-20 minutes.
These whales are fast strong swimmers with a cruising speed of 6.4-19.3 km/hr (4-12 mph). They are capable of accelerating to 48 km/hr (30 mph) when necessary.
Blue whales have the lowest and loudest voice of any whale. The frequency is as low as 14 hertz and the intensity or volume, the decibels, up to 200. Unlike humans, whales have no vocal cords in their larynx. They are believed to produce sound by moving air through tubed extensions of the larynx to nasal plugs located near the blowholes. Research using sonograms (device for visualizing sound), hydrophones, and other acoustical devices have shown that that these whales produce two sounds termed A or B calls. “A” calls appear to be made only by males and are described as a series of pulses that sound like someone gurgling mouthwash. “B” sounds are made by both sexes and seem to occur in feeding areas. They are more like a loud, low pitched groan or a rhythmic pounding that repeats and becomes a long moan. There is no variation among individuals within a population, the sounds of all sounding like the same note repeated over and over; however, nine variations have been described for nine populations around the world. Why these whales vocalize in these ways is being studied. A way to indicate fitness to a female calling as loud and low as the male can get? To navigate? To find krill patches? Time will tell.
In the process of changing from a land to water environment, whales have undergone many physiological and morphological changes. Among these adaptations are: streamlined bodies for efficient movement through water; forelimbs modified into flippers to aid in steering; hind limbs internalized remnants reducing drag; tail positioned horizontally to achieve a powerful up and down propulsion; hair replaced with under-skin blubber to provide warmth and buoyancy; structure of nostrils changed to blowholes that can be sealed off under water and position shifted to top of head to give ability to breath air before the rest of the body surfaces and while swimming at the surface without lifting the head; highly developed hearing that relies on an internal system of air sinuses and bones to detect sound instead of external ears; lung capacity that enables them to exchange 80-90% of lung air volume(humans can exchange only 17-20%) ; reproductive organs internalized to prevent drag when swimming; and countercurrent heat exchangers in the tongue that enable the whales to take in gallons of very cold water during feeding and still not become hypothermic.
The lifespan of these whales is estimated to be 40-80 years of age. Current research may prove that it is longer.
In late December 2012, NOAA announced that beginning in 2013, shipping lanes along the California coast would be adjusted to protect feeding and congregating blue, fin, and humpback whales from ship strikes. The lane changes include the approaches to San Francisco Bay, Santa Barbara Channel, and the ports of Los Angeles and Long Beach. In November 2012 the International Maritime Organization which governs shipping worldwide adopted the proposed changes.
Although there are encouraging reports that there may be a gradual increase in some population numbers of blue whales, so few survived the harpoons of whalers that recovery will be a slow process, especially for the southern blue whale population because of the excessive whaling that took place in the Antarctic. Estimated blue whale populations today are 400-1400 in the Southern Hemisphere, 5,000 in the North Pacific with about 2-3,000 of those in the “California” population, and possibly 1,000 in the North Atlantic. These are estimates only and are criticized by some researchers as being too high.
Initially blue whales were not a target species of whalers because their size and speed made them difficult to catch, kill, and retain. That changed beginning in 1864 with inventions of the explosive harpoon-gun and a method to inflate air into the dead whale’s body causing it to float; followed by steam and diesel powered catcher boats which shot and retrieved the whales handing them over to huge factory ships for processing. Blue whales now became the most targeted whale because of their profitability. The amount of oil available from one animal was 265-303 l (70-80 gal). About 350,000 blue whales were killed between 1910 and 1996 in the Antarctic and 8,200 in the North Pacific. Forty-eight blue whales were landed at Central California shore whaling stations as late as 1965. Finally in 1966 steps were taken to stop the slaughter before blue whales became extinct.
Whaling was banned in the Antarctic in 1966 and in the North Pacific in 1967. The Blue whales and other marine mammals received protection in the United States when the Marine Mammal Protection Act was adopted in 1972. The Southern Ocean was made a whale sanctuary in 1994. Today blue whales are listed as endangered both federally and by the IUCN Red List. There is no legislated subsistence hunting of these whales as there is for some other species.
Man-made ocean noise pollution from activities such as shipping, drilling operations, low frequency active sonar system testing by the military, studies of ocean climate transmitting sound at 195 decibels, etc.—any or all have the potential to interfere with blue whale communication. Research has indicated that these whales may depend on low frequency and high decibel sounds to communicate, find krill swarms, reproduce, and possible navigate.
California’s picky eaters: There are about 90 species of krill found worldwide. The two species preferred by the California blue whale population are Euphausia pacifica and Thysanoessa spinifera. Both are 15-25 mm (0.6-0.8 in) long. E. pacifica inhabits deeper water toward the margin of the continental shelf and beyond in water 200-400 m (656-1312 ft) deep during the day, migrating vertically to the surface at night to graze on phytoplankton. T. spinifera is a coastal species, inhabiting shallower water over the continental shelf, commonly at depths less than 150 m (492 ft) day and night. Researchers have determined the diet preferences of California’s blue whales by analyzing fecal specimens. The daily diet of juvenile blue whales appears to consist of half of each species, whereas adult blue whales seem to prefer the coastal species, T. spinifera.
Solving the mysteries of the blue whale: How do blue whales communicate and why? Where do they breed? How do they find clouds of krill? Which population migrates where? How long do they live? What is the population density in various parts of the world ocean? What is the impact of the ocean’s human caused noise pollution on their communication ? Scientists are working to solve the mysteries of the blue whale by using a combination of methods and technology not available to whalers who relied on visual observations to describe the whales and their behaviors. While visual observations are still a very important part of investigative studies, various research efforts today can include hydrophones permanently mounted on the ocean floor; hydrophones trailed behind boats under the water; photography and video of individuals; attachment of cameras and acoustical devices to the whales; skin biopsies for DNA analysis; laboratory analysis of fecal samples to determine food preferences; transmitters to send signals to and from satellites and data collection systems; radio tagging to record pitch, roll, and acceleration during dives; dive recorders to determine how feeding at depths occurs; etc.. A prominent blue whale researcher has said: “The mysteries of the blue whale will be solved, not by my generation or the next, but in the next—30 years from now”.
Sound Surveillance System (SOSUS): For nearly 40 years during the era of the Cold War the Navy used an array of hydrophones (underwater microphones) to listen for foreign submarines. SOSUS is permanently mounted on the bottom of the northern Atlantic and Pacific Oceans and the Caribbean Sea. SOSUS draws graph-like pictures of sound and also makes underwater recordings.
Through the years the Navy observers ignored the natural sounds of the ocean as they listened intently for the man-made noises of submarines. Observers were taught that one particular sound was that made by snapping shrimp. It was not until 1992 when the array was made available to marine mammal scientists that the “snapping shrimp” noise was shown to be that of whale vocalizations. Using SOSUS researchers were able to make more recordings of whale sounds in one year than had ever been deposited previously in the combined collection of all the world’s cetacean sound libraries. In 1993 a CD was made available to scientists of the first year’s vocalization of humpbacks, minke, finbacks, and blue whales called “Greatest Hits of Whales ‘93”. SOSUS is still being used in the study of whale migrations, population numbers, and behavior.