A digitally created image of a blue whale swimming underwater © naturepl.com / David Fleetham / WWF

A digitally created image of a blue whale swimming underwater © naturepl.com / David Fleetham / WWF

Blue whale

The largest animal ever known – the blue whale – sets a number of impressive records. It’s also one of the loudest and hungriest species on Earth.

Blue whales are simply enormous, ranging in length from 24-33 metres, and females are up to 10 metres longer than their male counterparts. Tipping the scales at up to 200 tonnes, a whale needs to eat about four tonnes of krill (shrimp-like crustaceans) daily. To put that into perspective, an adult male African elephant weighs six tonnes!


In order to eat, the blue whale expands its throat plates and takes in both water and krill, then it pushes the water out through its baleen plates, swallowing the krill that has stayed inside its mouth.

A blue whale's heart is the size of a small car and its heart beat can be detected more than three kilometres away. But that's nothing compared to its call. The low-frequency whistle is louder than a jet engine, reaching 188 decibels, compared to a jet engine's paltry 140 decibels. This call can be heard for hundreds of kilometres, which is handy if you’re scouring our vast oceans for a mate.


And if you’ve ever wondered whether a blue whale is actually blue… they are in fact a lightly mottled blue-grey, with light grey or yellow-white undersides.


Why it matters 

Whales are an important part of the marine food chain and play a huge role in maintaining the health of our oceans.

While it may be considered an endangered species, the blue whale is truly international, occurring in all oceans except the Arctic, and enclosed seas of course. Before whaling there may have been as many as 250,000; today, it is one of the world's rarest species, with the population of blue whales numbering just 10,000-25,000. Most biologists consider it among the most endangered of the great whales. Only one population, in the northeast Pacific off California, is showing real signs of recovery and it contains around 3,000 animals.

Blue whales require enormous amounts of food, but they’re a boon to rather than a burden on the ocean ecosystem. Their iron-rich poo is a really important source of nutrients in the marine food chain, promoting Southern Ocean productivity, which boosts fishery yields. These nutrients, particularly iron and nitrogen, are vital for phytoplankton, at the base of the food chain. Because plankton help to remove carbon dioxide from the atmosphere, you could go as far as to say that blue whales are carbon neutral. However you calculate it, whales are fertiliing their feeding grounds and providing sufficient nutrients to sustain krill populations.

Tail fluke of a blue whale diving. Marissa, Sri Lanka © Richard Barrett / WWF-UK

Balaenoptera musculus

Species Bio

Common Name

Blue whale

Scientific Name

Balaenoptera musculus


Length: 24-33 m / Weight: Up to 200 tonnes

Population: 10,000-25,000



Listed as Endangered (IUCN Red List)


Although there is debate surrounding the taxonomy of blue whales, there are five distinct subspecies: Antarctic blue whales in the Southern Ocean (Balaenoptera musculus intermedia); North Atlantic and North Pacific blue whales (Balaenoptera musculus musculus); Pygmy blue whales, found in the Southern Indian Ocean (Balaenoptera musculus brevicauda); Northern Indian Ocean (Balaenoptera musculus indica) and South Pacific Ocean (Balaenoptera musculus unnamed species) whales.


Did you know?

Blue whales dive for 10-20 minutes, and usually feed at depths of less than 100 metres.


Climate change, ship strikes and entanglement in fishing gear are the primary threats faced by blue whales. Additional threats that could potentially affect whale populations include anthropogenic noise, habitat degradation, pollution and vessel disturbance.


Noise pollution
Blue whales use sound to find their partners and perhaps location of topographic features and prey. Man-made noise can potentially mask their vocalisations, throwing them off-course and disrupting both movements and breeding. Potential sources of man-made underwater noise in Australian waters include seismic surveys for oil, gas and geophysical exploration; industrial development (such as drilling, pile-driving, blasting and dredging); gas processing and shipping.

Increased shipping traffic
Vessels can collide with whales or disrupt their behaviour. For millions of years, whales have cruised the world's oceans with hardly a care, their sheer size leaving them largely free from danger. The blue whale has never had to learn to defend itself, which makes blue whales particularly susceptible to deadly collisions with ships.

Entanglement in fishing gear
Entanglements can be very dangerous for whales. They may drag gear around for a long time, with the line having a 'ball-and-chain' effect, limiting its ability to feed and eventually compromising its health.

What you can do to help

Climate change is a growing threat to whales, so we need to send a message to our leaders that warming must be limited to under 2° Celsius.

Support efforts to improve fishing gear by only buying seafood that is Marine Stewardship Council (MSC) certified. This can help to reduce the incidence of marine bycatch, which kills whales and other marine life like turtles, dolphins and seabirds.

Recommended reading

Blue whale (Balaenoptera musculus) surfacing in front of the WWF research team, Gulf of Corcovado © WWF / Francisco Viddi


Blue whale satellite tagging

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