About the Species
Blue whales are the largest animals ever to live on our planet. They feed almost exclusively on krill, straining huge volumes of ocean water through their baleen plates (which are like the teeth of a comb). Some of the biggest individuals may eat up to 6 tons of krill in 1 day.
Blue whales are found in all oceans except the Arctic Ocean. There are five currently recognized subspecies of blue whales.
The number of blue whales in the world’s oceans is only a small fraction of what it was before modern commercial whaling significantly reduced their numbers during the early 1900s, but populations are increasing globally. Today, blue whales are listed as endangered under the Endangered Species Act. The primary threats currently facing blue whales are vessel strikes and entanglements in fishing gear.
NOAA Fisheries and its partners are dedicated to conserving and rebuilding blue whales worldwide. We use a variety of innovative techniques to study, protect, and rescue these endangered animals. We engage our partners as we develop regulations and management plans that foster healthy fisheries and reduce the risk of entanglements, create whale-safe shipping practices, and reduce ocean noise.
Blue whales were significantly depleted by commercial whaling activities worldwide. The latest stock assessments of blue whales include data for various stocks, including areas of the North Pacific and western North Atlantic Oceans.
- Throughout Its Range
CITES Appendix II
- Throughout Its Range
- Throughout Its Range
- Throughout Its Range
Blue whales have a long body and generally slender shape. Their mottled blue-gray color appears light blue under water—hence their name, the blue whale. The mottling pattern is variable and can be used to identify individuals.
Antarctic blue whales are generally larger than other blue whale subspecies. For example, in the North Atlantic and North Pacific, blue whales can grow up to about 90 feet, but in the Antarctic, they can reach up to about 110 feet and weigh more than 330,000 pounds. Like other baleen whales, female blue whales are somewhat larger than males.
Behavior and Diet
Blue whales live in all the world's oceans except the Arctic. They sometimes swim in small groups but usually alone or in pairs. They generally spend summers feeding in polar waters and undertake lengthy migrations towards the Equator as winter arrives.
Blue whales typically cruise the ocean at more than 5 miles an hour but can accelerate to more than 20 miles an hour for short bursts. They are among the loudest animals on the planet, emitting a series of pulses, groans, and moans, and it is thought that in good conditions, blue whales can hear each other up to 1,000 miles away. Scientists think they use these vocalizations not only to communicate and—along with their excellent hearing—to sonar-navigate the dark ocean depths.
The primary and preferred diet of blue whales is krill—tiny shrimp-like animals. Fish and copepods (tiny crustaceans) may occasionally be part of the blue whale’s diet. When these marine mammals hunt for food, they filter feed by swimming toward large schools of krill with their mouth open, then push the water out of their mouth with their tongue while keeping the krill trapped inside their baleen bristles.
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 remain in certain areas year-round. Information about distribution and movement varies with location, and migratory routes are not well-known. In general, distribution is driven largely by food requirements—they occur in waters where krill is 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, in the shelf waters of the eastern United States, and infrequently in the Gulf of Mexico and the Caribbean.
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 have been observed often in the Gulf of California from December through March. Thus, at least some calves may be born in or near the Gulf of California; this area is probably 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 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.
Lifespan & Reproduction
Blue whales are among Earth's longest-lived animals. Their average lifespan is estimated at around 80 to 90 years. Scientists have discovered that they can closely estimate the animal’s age by counting the layers of a deceased whale's waxlike earplugs, they can get a close estimate of the animal's age.
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, and that blue whale calves are nursed for about 6 to 7 months. Most reproductive activity, including births and mating, takes place during the winter. Weaning probably occurs on, or en route to, summer feeding areas. The average calving interval is probably 2 to 3 years. The age of sexual maturity is thought to be 5 to 15 years.
Inadvertent 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 ship traffic.
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, or gillnets. Once entangled, whales may drag and swim with 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 include ocean noise, habitat degradation, pollution, vessel disturbance, and long-term changes in climate.
Blue whales are protected under both the Endangered Species Act and the Marine Mammal Protection Act. They have been listed as endangered under the ESA since 1970. This means that the blue whale is in danger of extinction throughout all or a significant portion of its range. NOAA Fisheries is working to protect this species in many ways.
Recovery Planning and Implementation
Under the ESA, NOAA Fisheries is required to develop and implement recovery plans for the conservation and survival of listed species. The ultimate goal of the Blue Whale Recovery Plan is to recover the species, with an interim goal of down-listing its status from endangered to threatened. This consists of eight objectives:
- Determine the blue whale stock structure both in and out of U.S. waters.
- Estimate population size and monitor abundance trends.
- Identify and protect essential habitats.
- Reduce or eliminate human-caused death and injuries.
- Minimize any negative effects of directed vessel interactions with whales.
- Maximize efforts to acquire scientific data from dead, stranded, and entangled blue whales.
- Coordinate state, federal, and international efforts to implement recovery actions.
- Establish criteria for deciding whether to delist or down-list blue whales.
NOAA Fisheries is working to minimize effects from human activities that are detrimental to the recovery of blue whale populations. We implement similar conservation efforts for the North Atlantic and North Pacific blue whale populations given the similar management and research needs. Also, since blue whales move freely across international borders, recovery efforts are not confined to U.S. waters.
Reducing Vessel Strikes
Collisions between whales and large vessels can injure or kill the whales and damage the vessels, but they often go unnoticed and unreported. NOAA Fisheries has taken both regulatory and non-regulatory steps to reduce the threat of vessel collisions to whales. The steps include:
- Learn when the seasonal abundance of large whales are in your shipping lanes; listen and be aware of advisories.
- Consult the Local Notice to Mariners in your area or Coast Pilot for more information.
- Keep a sharp lookout for whales; including posting extra crew on the bow to watch, if possible.
- Reduce speeds while in advisory zones or in areas of high seasonal or local whale abundance.
- If practicable, re-route vessel to avoid areas of high whale abundance.
The most effective way to reduce collision risk is to keep whales and vessels apart; where this is not possible, vessels need to slow down and keep a lookout.
Overseeing Marine Mammal Health and Stranding Response
We work with volunteer networks in all coastal states to respond to marine mammal strandings including large whales. When stranded animals are found alive, NOAA Fisheries and our partners assess the animal’s health. When stranded animals are found dead, our scientists work to understand and investigate the cause of death. Although the cause often remains unknown, scientists can sometimes identify strandings due to disease, harmful algal blooms, vessel strikes, fishing gear entanglements, pollution exposure, and underwater noise. Some strandings can serve as indicators of ocean health, giving insight into larger environmental issues that may also have implications for human health and welfare.
Minimizing Whale Watch Harassment
Whale SENSE is a voluntary education and recognition program in the U.S. Atlantic and Alaska Regions. NOAA Fisheries and partners developed Whale SENSE in collaboration with the whale watching industry to recognize whale watching companies committed to responsible practices.
Participating companies agree to:
- Stick to the regional whale watching guidelines.
- Educate naturalists, captains, and passengers to have SENSE while watching whales.
- Notify and report whales in distress.
- Set an example for other boaters.
- Encourage ocean stewardship.
Reducing Ocean Noise
Noise pollution threatens whale populations, interrupting their normal behavior and driving them away from areas important to their survival. Increasing evidence suggests that exposure to intense underwater sound in some settings may cause some whales to strand and ultimately die. NOAA Fisheries is investigating all aspects of acoustic communication and hearing in marine animals, as well as the effects of sound on whale behavior and hearing. In 2016, NOAA Fisheries issued technical guidance for assessing the effects of anthropogenic sound on marine mammals’ hearing.
The blue whale is listed as endangered throughout its range under the ESA and is thus listed as depleted throughout its range under the MMPA.
Internationally, blue whales received complete legal protection from commercial whaling in 1966 under the International Convention for the Regulation of Whaling.
Regulatory Actions & Documents
NOAA Fisheries conducts various research activities on the biology, behavior, and ecology of the blue whale. The results of this research are used to inform management decisions and enhance recovery efforts for this endangered species.
Scientists working on the WhaleWatch project are using advanced technologies to predict where blue whales are likely to be in near real-time off the U.S. West Coast. This near real-time information helps reduce human impacts on whales by showing where they may be most at risk from threats such as vessel strikes, entanglements, and loud underwater sounds. Scientists developed model estimates using habitat-based models of whale occurrence that combine satellite tracking of whales with information on the environment.
Determining the size of the blue whale population—and whether it is increasing or decreasing —helps resource managers assess the success of the conservation measures enacted. NOAA Fisheries scientists collect population information on blue whales from various sources and present this data in an annual stock assessment report.
NOAA Fisheries’ research cruises investigate the whales’ habitat preferences and feeding ecology and conduct photographic and genetic identification. Information from this research can be used in management actions that protect the blue whale and reduce human-related deaths.
Other research is focused on the acoustic environment of blue whales. This research involves increasing our understanding of the basic acoustic behavior of whales, dolphins, and fish; mapping the acoustic environment; assessing their seasonal distribution; and developing improved methods to locate cetaceans using autonomous gliders and passive acoustic arrays.
Unusual Mortality Events
To understand the health of marine mammal populations, scientists study unusual mortality events—also known as UMEs. Understanding and investigating marine mammal UMEs is important because they can serve as indicators of ocean health, giving insight into larger environmental issues that may also have implications for human health and welfare.
Learn more about UMEs
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