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.
Blue Whale Balaenoptera musculus
The largest animals ever to have lived on the planet (surpassing even dinosaurs), blue whales inspire awe and wonder with all the records they break: The largest blue whale ever recorded was 33 m long; a blue whale’s heart is the size of a small car; a child could crawl through a blue whale’s arteries; and blue whales produce the loudest sound on earth – even if it is too low in frequency for humans to hear it. There are at least five recognized sub-species of blue whale that occur in different ocean basins. These are
- B. m. musculus, Northern blue whale
- B. m. intermedia, Antarctic blue whale
- B. m. indica, Northern Indian Ocean blue whale
- B. m. brevicauda, Pygmy blue whale
- B. m. un-named subsp., Chilean blue whale.
Pygmy blue whales are smaller and are generally restricted to the Southern Hemisphere including the Indian Ocean. “True” blue whales refer to the larger musculus, intermedia, and indica subspecies. Antarctic blue whales (intermedia) are the largest of the species, but have been severely depleted after decades of whaling. Blue whales are usually found offshore, and their seasonal migrations and breeding and feeding grounds are generally poorly understood. However, there are a few places where they can be seen with some regularity during whale watching trips, such as the Gulf of California in Mexico, the Gulf of St. Lawrence in Canada, the California coast of the United States, and Sri Lanka.
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Blue whale lifting its tail flukes. Photo courtesy of Paula Olson.
Pygmy blue whale in Western Australia. Photo courtesy of Chris Johnson
Not to be confused with
Blue whales have the sleek and slender body shape of other rorqual whales like Bryde’s, sei and fin whales. However, their great size and unique blue mottled colouration should make them easily distinguishable from any other species.
Distribution
Blue whales occur worldwide in all major oceans except the Arctic 1,2 . They are also absent from some regional seas such as the Mediterranean, Okhotsk and Bering seas. They are almost never seen off of eastern South America or eastern Australia. Despite their wide distribution the blue whales are not often encountered, partly due to their reduced numbers, and party because they generally occur in offshore waters, with only a few known coastal breeding and feeding areas.
Native to the following countries: Angola; Argentina; Australia; Bahamas; Bangladesh; Benin; Bermuda; Brazil; Cameroon; Canada; Cape Verde; Chile; China; Cocos (Keeling) Islands; Colombia; Comoros; Cook Islands; Costa Rica; Côte d’Ivoire; Djibouti; Ecuador; El Salvador; Equatorial Guinea; Eritrea; Falkland Islands (Malvinas); Faroe Islands; France; French Southern Territories; Gabon; Ghana; Gibraltar; Greece; Greenland; Grenada; Guatemala; Iceland; India; Indonesia; Iran, Islamic Republic of; Iraq; Ireland ; Japan; Kenya; Madagascar; Malaysia; Maldives; Marshall Islands; Mauritania; Mauritius; Mexico; Morocco; Mozambique; Myanmar; Namibia; New Caledonia; New Zealand; Nicaragua; Nigeria; Northern Mariana Islands; Norway; Oman; Pakistan; Palau; Panama; Peru; Philippines; Pitcairn; Portugal; Russian Federation; Saint Helena, Ascension and Tristan da Cunha (Tristan da Cunha); Saint Pierre and Miquelon; Sao Tomé and Principe; Senegal; Seychelles; Somalia; South Africa; South Georgia and the South Sandwich Islands; Spain; Sri Lanka; Taiwan, Province of China; Tanzania, United Republic of; Thailand; Timor-Leste; Togo; United Kingdom; United States; Uruguay; Western Sahara; Yemen
Blue whale global distribution. Adapted by Nina Lisowski from Jefferson, T.A., Webber, M.A. and Pitman, R.L. (2015). “Marine Mammals of the World: A Comprehensive Guide to Their Identification,” 2nd ed. Elsevier, San Diego, CA. Copyright Elsevier: http://www.elsevier.com.
Biology and Ecology
Feeding
Throughout their range, blue whales feed predominantly on small shrimp-like crustaceans called krill. While the species of krill may differ from one ocean basin to another, the manner in which the whales feed is the same: usually lunge feeding through large swarms of prey, either by coming up directly underneath them with open mouths and throat pleats expanded, or by swimming on their sides with open mouths. While doing this, blue whales can engulf more than 100 tons of water and krill, then close their mouths and contract their throat pleats, thus forcing water out of their mouths and straining the krill through their baleen plates.
Social structure, reproduction and growth
Very little is known about blue whale mating and calving, although a few nursing grounds have been identified, for example in the Gulf of California. Blue whale calves are generally born in the winter after a 10- 12-month gestation period, and remain with their mothers for roughly 8 months, during which they can double in size, gaining up to 90 kg per day from drinking the mother’s rich milk (whale milk is almost more the consistency of cottage cheese with a 30-40% fat content). Blue whales are usually seen singly or in pairs, and do not form large mating aggregations like other species, but they may gather in larger numbers where good feeding opportunities are available. With such a sparse distribution throughout the world’s oceans, blue whales use powerful vocalizations to communicate with each other across long distances. Blue whales’ calls are generally infrasonic (17-20 Hz), and too low for humans to hear, but at 188 decibels, they are one of the loudest and lowest sounds produced by any animal. 1
Antarctic Krill, Photo credit: https://commons.wikimedia.org/wiki/File:Antarctic_krill_(Euphausia_superba).jpg
Blue Whale in Loreto Bay, Gulf of California, Mexico. Photo courtesy of Diane Gendron.
SPECIES IN DETAIL
CONSERVATION STATUS: Endangered – Protected
CLIMATE CHANGE: Not Applicable
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.
Geographic Distribution
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).
Physical Characteristics
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.
Where They Live
Blue whales are found in all oceans except the Arctic. They generally migrate seasonally between summer feeding grounds and winter breeding grounds, but some evidence suggests that individuals in certain areas might not migrate at all. Information about distribution and movement varies with location, and migratory routes are not well known. In general, distribution is driven largely by food availability—they occur in waters where krill are concentrated.
In the North Atlantic Ocean, their range extends from the subtropics to the Greenland Sea. Blue whales have been sighted in the waters off eastern Canada and in the shelf waters of the eastern United States.
Along the West Coast of the United States, eastern North Pacific blue whales are believed to spend winters off of Mexico and Central America. They likely feed during summer off the U.S. West Coast and, to a lesser extent, in the Gulf of Alaska and central North Pacific waters.
Blue whales with young calves are regularly observed in the Gulf of California (Sea of Cortez) from December through March. It is believed that this area is an important calving and nursing area for the species.
In the northern Indian Ocean, there is a “resident” population. Blue whale sightings, strandings, and acoustic detections have been reported from the Gulf of Aden, Arabian Sea, and across the Bay of Bengal. The migratory movements of these whales are largely unknown but may be driven by oceanographic changes associated with monsoons.
In the Southern Hemisphere, Antarctic blue whales occur mainly in relatively high latitude waters south of the “Antarctic Convergence” and close to the ice edge in summer. They generally migrate to middle and low latitudes in winter, although not all whales migrate each year. Pygmy blue whales (Balaenoptera musculus brevicauda)—a subspecies—are typically distributed north of the Antarctic Convergence and are most abundant in waters off Australia, Madagascar, and New Zealand. An unnamed subspecies of blue whale is found in the southeastern Pacific Ocean, particularly in the Chiloense Ecoregion, and migrates to lower latitude areas, including the Galapagos Islands and the eastern tropical Pacific.
World map providing approximate representation of the blue whale’s range.
Lifespan & Reproduction
Blue whales’ average lifespan is estimated at around 80 to 90 years. Scientists can estimate the age of whales by counting the layers of wax-like earplugs collected from deceased animals.
Scientists know little about the life history of the blue whale. The best available science suggests the gestation period is approximately 10 to 12 months. Weaning probably occurs at around 6 to 7 months on, or en route to, summer feeding areas. The age of sexual maturity is thought to be 5 to 15 years. Most reproductive activity, including births and mating, takes place during the winter. The average calving interval is probably 2 to 3 years.
Threats
Vessel Strikes
Vessel strikes can injure or kill blue whales. Vessel strikes have killed blue whales throughout their range, but the risk is much higher in some coastal areas with heavy vessel traffic, like ports and in shipping lanes, and from larger vessels and vessels traveling at high speeds.
Entanglement in Fishing Gear
Blue whales can become entangled in fishing gear, either swimming off with the gear attached or becoming anchored. Blue whales can become entangled in many different gear types, including traps, pots, and nets. Once entangled, whales may drag the attached gear for long distances, ultimately resulting in fatigue, compromised feeding ability, or severe injury, which may lead to reduced reproductive success and death.
Additional Threats
Additional possible threats to blue whales that are less understood include ocean noise, habitat degradation, pollution, vessel disturbance, and climate change.
