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 hang from the roof of the mouth and work like a sieve). 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 generally larger than males.
Behavior and Diet
Blue whales sometimes swim in small groups but are more often found 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 swim at about 5 miles an hour while they are feeding and traveling, 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 the right oceanographic conditions, blue whales can hear each other up to 1,000 miles away. Scientists think they use these vocalizations to communicate and—along with their excellent hearing—perhaps 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 blue whales 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 plates.
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 availability—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 are regularly observed in the Gulf of California (Sea of Cortez) from December through March. Thus, it is believed that; this area is likely 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 can estimate age by counting the layers of waxlike earplugs collected from deceased whales.
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. Weaning probably occurs 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.
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.
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 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.
In the Spotlight
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. In addition, because blue whales move freely across international borders, recovery efforts are not confined to U.S. waters.
Reducing Vessel Strikes
Collisions between whales and 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. Precautions vessel operators can take include:
- Learn when the seasonal abundance of large whales are in shipping lanes; listen and be aware of advisories.
- Consult the Local Notice to Mariners in Coast Pilot for more information.
- Keep a sharp lookout for whales, including posting additional crew lookouts on the bow, if possible.
- Reduce speeds while in advisory zones or in areas of high seasonal or local whale abundance.
- If practicable, re-route vessels to avoid areas of high whale abundance.
The most effective way to reduce collision risk is to keep whales and vessels separated by great distances; where this is not possible, vessels need to slow down and keep a lookout.
Marine Mammal Unusual Mortality Events
Under the Marine Mammal Protection Act, an unusual mortality event (UME) is defined as "a stranding that is unexpected; involves a significant die-off of any marine mammal population; and demands immediate response." To understand the health of marine mammal populations, scientists study unusual mortality events.
Minimizing Whale Watch Disturbance
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.
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.
Reducing Ocean Noise
Noise pollution can threaten whale populations, interrupting their normal behavior and driving them away from areas important to their survival. 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 2018, NOAA Fisheries issued revised 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.
Key Actions and Documents
Incidental Take Authorization: Lamont-Doherty Earth Observatory Marine Geophysical Survey in the Aleutian Islands
- Issued IHA (pdf, 18 pages)
- Application (pdf, 126 pages)
- Final Environmental Assessment
- Finding of No Significant Impact (pdf, 14 pages)
- Public Comments (external link)
- References (pdf, 6 pages)
Incidental Take Authorization: THwaites Offshore Research (THOR) Project in the Amundsen Sea, Antartica
- Issued IHA (pdf, 11 pages)
- Draft IHA (pdf, 11 pages)
- Application (pdf, 101 pages)
- Biological Opinion (pdf, 205 pages)
- References (pdf, 16 pages)
Incidental Take Authorization: Scripps Institute of Oceanography Low-Energy Geophysical Survey in the South Atlantic Ocean
- Issued IHA (pdf, 16 pages)
- IHA Application (pdf, 114 pages)
- References (pdf, 42 pages)
- Biological Opinion (pdf, 188 pages)
- Draft IHA (pdf, 15 pages)
- Issued IHA (pdf, 13 pages)
- IHA application (pdf, 115 pages)
- Draft IHA (pdf, 13 pages)
- References (pdf, 45 pages)
- Biological Opinion (pdf, 161 pages)
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 providing information on where they may be most at risk from threats such as vessel strikes, entanglements, and loud underwater sounds. Scientists developed habitat-based model estimates 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 these data in an annual stock assessment report.
NOAA Fisheries’ research cruises investigate blue whales’ habitat preferences and feeding ecology and conduct photographic and genetic identification. Information from this research is 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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Our Passive Acoustics Research Group frequently makes the news. This page links to articles and other media featuring our staff and their research.
Despite the end of commercial whaling, many whale populations have been slow to increase in number. Blue whales are classified as an endangered species under the Endangered Species Act, and there is concern that human activities may be responsible for…