FAQ: Frequently Asked Questions about Cetaceans

~90cetacean species worldwide
25+species in French waters
55questions covered in detail
50 Maof evolution since their land-dwelling ancestors

Each of the 55 questions below leads to a detailed, sourced answer page. Cannot find your question? Contact us: we add to this page regularly.

Identifying and telling cetaceans apart

What is the difference between a whale, a sperm whale and a dolphin?

All are cetaceans. Whales in the strict sense (mysticetes) have baleen and no teeth. The sperm whale and the dolphins are odontocetes. Genetically, the sperm whale is closer to the dolphin than to the blue whale. See our full guide.

What is the difference between a dolphin and a porpoise?

Dolphins (Delphinidae) have an elongated rostrum, conical teeth and a falcate dorsal fin. Porpoises (Phocoenidae) have a short snout with no marked rostrum, spade-shaped teeth and a triangular dorsal fin. See the species page for the harbour porpoise.

Is a whale a fish?

No. A whale is a marine mammal: it breathes air at the surface, gives birth to live young, suckles them, is endothermic (warm-blooded) and even grows an embryonic coat of hair that disappears before birth. See cetacean evolution, from land mammal to cetacean.

Do whales have teeth?

No, baleen whales (mysticetes) have no teeth; they have keratin plates called baleen. Sperm whales, dolphins, porpoises and killer whales (all odontocetes), by contrast, do have teeth. See our page on baleen.

How many cetacean species are there?

About 94 living species are recognised, divided between the mysticetes (~15 species) and the odontocetes (79 species). See the mysticetes and the odontocetes.

How can you recognise a cetacean from its blow?

The blow is often visible before the animal itself, and its shape gives away the species: a 12 metre vertical column in the blue whale, a V-shaped double jet in the right whale, an oblique blow angled forward and to the left in the sperm whale. See our seven profiles for recognising a cetacean from its blow.

Why are some cetaceans white or mottled?

Albinism, leucism and local morphs produce striking individuals: Migaloo the white humpback whale, the pink river dolphins of the Amazon and the Indus, melanistic killer whales. See our database of pigmentation variants.

Size, weight and performance

What is the largest animal in the world?

The blue whale (Balaenoptera musculus) is the largest animal that has ever lived on Earth: up to 30 metres long and 180 tonnes. It exceeds every dinosaur known. See the species page for the blue whale and the scale comparator.

How much does a blue whale weigh?

An adult blue whale weighs between 100 and 180 tonnes. At birth the calf already weighs about 2.5 tonnes and measures 7 metres, and it gains about 90 kg a day while it is suckling. See the scale comparator.

How deep does the sperm whale dive?

The sperm whale dives routinely between 300 and 1,000 m, but can descend to more than 3,000 m. Cuvier’s beaked whale outdoes it, with a documented record of 2,992 m. See the diving records.

How long can a whale stay underwater?

The humpback whale dives for about 15 minutes, the sperm whale for 45 to 90 minutes, and Cuvier’s beaked whale holds the outright record with a 222 minute breath-hold (Quick et al., 2020). See diving physiology.

Which is the fastest whale?

The sei whale can reach 55 km/h at top speed. The killer whale reaches 56 km/h in a sprint. See swimming performance.

How long does a whale live?

The sperm whale lives 60 to 70 years, the killer whale 50 to 80, the common bottlenose dolphin 40 to 50. The bowhead whale holds the record: some individuals are reported to have passed 200 years. See cetacean life cycles.

How many calories does a whale consume in a day?

A blue whale consumes about 600,000 kcal a day, the equivalent of 240 humans. Relative to its mass, however, its metabolism is remarkably economical. See the energy and metabolism comparator.

Why do cetaceans swim so efficiently?

Because they converge on a physical optimum. The Strouhal number, which compares tail-beat frequency to speed, falls between 0.25 and 0.35 in every high-performance swimmer, from the dolphin to the tuna by way of the hummingbird. See our page on hydrodynamics and the Strouhal number.

How many vertebrae and teeth does a cetacean have?

It varies enormously: a single tooth in the narwhal, its tusk, against 240 to 260 in the Amazon river dolphin, and 600 baleen plates in the bowhead whale. The beluga is the only cetacean that keeps unfused cervical vertebrae. See the anatomical counts.

Anatomy and physiology

What is the melon for in odontocetes?

The melon is an acoustic lens of specialised fats that focuses echolocation clicks into a directional beam pointing forward. In the sperm whale it becomes the colossal spermaceti organ. → Read the detailed answer

What is the rete mirabile and what does it do?

A dense vascular network that provides countercurrent thermoregulation, protects the brain during the pressure changes of a dive and stores oxygenated blood. → Read the detailed answer

How do sperm whales dive without decompression sickness?

Their lungs collapse from 100 m down, preventing nitrogen uptake. Myoglobin stores oxygen, and bradycardia reduces consumption. → Read the detailed answer

What is a cetacean’s body temperature?

Between 36 and 37 °C, as in humans. Maintained by the insulating blubber and the rete mirabile. → Read the detailed answer

How are whale calves born?

Birth takes place at sea, tail first to avoid drowning, and the calf is pushed up to the surface to breathe. It suckles underwater on a milk containing 30-50% fat. → Read the detailed answer

Do cetaceans see well underwater?

Their vision is monochromatic but suited to every depth. It is hearing that dominates above all, up to 180 kHz in odontocetes, while taste and smell are all but atrophied. See our page on the senses of cetaceans.

What diseases do cetaceans suffer from?

Morbillivirus, brucellosis, Anisakis parasites, tumours associated with PCBs: cetaceans are subject to a whole range of conditions, often made worse by chemical pollution. See our database of cetacean pathology and health.

What are those shells attached to the skin of whales?

Barnacles, cemented to the epidermis, alongside “whale lice”, remoras and diatoms. The famous callosities of right whales are covered in them. See our page on epibionts and symbioses, which distinguishes commensals, parasites and mutualists.

Why do proportions vary so much from one species to another?

Every silhouette reflects a way of life: the flippers of the humpback whale reach a third of its body length, and the skull of the sperm whale is markedly asymmetrical. See our database of comparative morphometrics.

Communication and acoustics

How does echolocation work in odontocetes?

The clicks are produced in the nasal passages by phonic lips, focused by the melon, and the echo is picked up by the lower jaw to reconstruct an acoustic image. → Read the detailed answer

How do whales communicate?

Baleen whales use low-frequency sounds that travel hundreds of kilometres. Male humpback whales produce complex structured songs. Odontocetes use clicks, whistles and burst pulses. The sperm whale communicates through rhythmic sequences called codas. See the acoustic profile and our sound library.

How do blue whales communicate over thousands of km?

Infrasonic sounds (< 20 Hz) that travel in the SOFAR channel, a natural waveguide between 600 and 1,200 m deep. → Read the detailed answer

What is a signature whistle in the common bottlenose dolphin?

A unique whistle belonging to one individual, the acoustic equivalent of a given name. Other dolphins can copy it to call that animal by name. → Read the detailed answer

What is the “52 Hz whale”?

An unidentified cetacean detected in 1989 by William Watkins, singing at an atypical frequency. Never seen visually, nicknamed “the loneliest whale”. → Read the detailed answer

What is the loudest animal in the world?

The sperm whale. Its clicks reach 230 decibels, the acoustic equivalent of a rocket launch. See the cetacean records.

Why do humpback whales sing?

Only the males sing, mainly on the breeding grounds. Several hypotheses have been put forward: a sexual signal, a territorial marker, or a means of cohesion between males. See the species page for the humpback whale and our sound library.

Why do whales leap out of the water?

Several hypotheses have been offered for these leaps (breaching): an acoustic signal, parasite load, play, a social or sexual display. See aquatic behaviour.

Do dolphins sleep?

Yes, but in a particular way: only one cerebral hemisphere sleeps at a time (unihemispheric sleep). This allows them to go on breathing voluntarily. See our page on cetacean sleep.

How does a dolphin breathe?

Through a blowhole set on top of the head. Breathing is voluntary: the dolphin has to come up to the surface consciously. See the interactive anatomy.

Can you listen to cetaceans live?

Yes. Several hydrophone networks stream the sound of the sea continuously, sometimes the song of a killer whale or the click of a sperm whale: Orcasound and OrcaLab in the north-east Pacific, Ocean Networks Canada and its cabled observatories. See our selection of live hydrophones.

How are cetaceans monitored by sound?

Through passive acoustic monitoring: autonomous hydrophones listen to the ocean around the clock, from the former SOSUS military network to the current OOI and SAMBAH systems. See our page on passive acoustic monitoring.

Cognition, culture and social life

Are cetaceans really intelligent?

Yes, by most of the criteria of comparative cognition: self-awareness (the mirror test), social learning, cultural transmission, symbolic communication, tool use, mourning. → Read the detailed answer

Do sperm whales have a culture?

Yes. They are organised into cultural clans that share a coda dialect and distinct behaviours, transmitted matrilineally. → Read the detailed answer

Do killer whales hunt in groups?

Yes, almost always. Each ecotype has its own cultural techniques: strand feeding, wave washing, silent hunting of marine mammals. → Read the detailed answer

How do humpback whales hunt with bubble nets?

Several whales cooperate: one builds a spiral wall of bubbles, another gives a call, and all of them rise together with their mouths open. → Read the detailed answer

Do cetaceans use tools?

Yes, and these techniques are passed on culturally from one generation to the next, which makes them one of the strongest arguments for their intelligence. See our tool catalogue, which documents a dozen such practices around the world.

Which experiments have tested the intelligence of cetaceans?

From mirror self-recognition (Reiss and Marino, 2001) to the vocal imitation of the killer whale Wikie (Abramson, 2018), cetaceans have passed tests designed for the great apes. See our fifteen foundational cognitive experiments.

How long do social bonds last in cetaceans?

The whole range exists, from the solitary sperm whale on a dive to a mega-group of 1,000 common dolphins. The alliances of the Shark Bay common bottlenose dolphins last more than twenty years, and sperm whale matrilines run across generations. See our social cohesion comparator.

Feeding and reproduction

What do whales eat?

Baleen whales eat mainly krill and small fish. The sperm whale eats cephalopods. The killer whale has a very varied diet: fish, seals, other cetaceans, even sharks. See cetacean diets.

What does the sperm whale eat? Can it eat a giant squid?

Yes. The scars on its skin and the squid beaks found in its stomachs prove that it hunts Architeuthis and Mesonychoteuthis regularly. → Read the detailed answer

How do blue whales feed?

By engulfment (lunge feeding): the whale accelerates with its mouth open. Its throat pleats stretch out like a concertina, allowing it to take in up to 90,000 litres of water in a single mouthful. See cetacean diets.

How long is gestation in a whale?

Between 10-11 months (porpoise) and 16 months (sperm whale). On average 11 to 13 months. A single calf per birth, every 2 to 6 years. See the life cycles.

How long does a calf stay with its mother?

From 4 months (porpoise) to a whole lifetime (resident killer whales). The sperm whale stays with its maternal unit for about 10 years on average. → Read the detailed answer

How much milk does a calf drink each day?

A blue whale produces up to 220 litres a day, at 50% fat: the richest composition in the animal kingdom. Its calf gains 90 kg a day. See our comparator of lactation in cetaceans.

Are cetaceans faithful to one partner?

Rarely. The strategies range from competition between male humpback whales to the multi-level alliances of the Shark Bay common bottlenose dolphins. See our comparator of mating systems, documented for 18 species.

Habitat, migration and watching

Why do whales migrate every year?

To combine feeding in productive polar waters with breeding in warm tropical waters, which are essential to calves with little insulation. → Read the detailed answer

How do cetaceans find their way over long distances?

Magnetoreception is likely, along with underwater topographic memory, acoustic cues, ocean currents and temperatures. → Read the detailed answer

How many cetaceans live in France?

More than 25 species have been recorded in French waters (mainland and overseas). The Pelagos Sanctuary in the Mediterranean alone holds 8 regular species. See the map of cetaceans in France.

Where can you see whales in France?

In the Mediterranean (Pelagos, Côte d’Azur, Corsica), in the Bay of Biscay, in French Polynesia (August to October), in the French Antilles (January to May). See our guide to watching in the Mediterranean.

When should you watch for whales in the Mediterranean?

From June to September, when the krill rise. The peak falls in July and August. Striped dolphins are visible all year round. See watching in the Mediterranean and the watching calendar.

Which cetaceans live in fresh water?

The Ganges river dolphin, the boto (Amazon), the tucuxi. Historically the baiji of the Yangtze, considered functionally extinct since 2006. See the freshwater cetaceans.

Can you swim with wild cetaceans?

It is discouraged and often regulated. The risks: transmission of pathogens, disruption of behaviour. Prefer watching from a boat certified High Quality Whale Watching. See the whale watching labels.

How far does a whale travel in a year?

The grey whale holds the mammal record: 20,000 km there and back. The humpback whale covers 8,000 km on an almost straight course, one of the most precise navigations known. See our comparator of annual migrations.

At what temperature and at what depth does each species live?

Each occupies a precise niche: Cuvier’s beaked whale between 200 and 3,000 metres, the bowhead whale at the edge of the sea ice between -1 and 4 °C, tropical dolphins at the surface between 24 and 30 °C. See our mapping of thermal and bathymetric preferences.

What are the best watching sites in the world?

It depends on the species: the sperm whale in the Azores or Dominica, the killer whale in Norway, at Vancouver or at Punta Norte, the blue whale in Sri Lanka, at Monterey or in the Saguenay. See our database of global hotspots by species.

Do ocean currents determine where cetaceans live?

Largely. The Humboldt Current feeds the cetaceans of Peru, and the SOFAR channel carries blue whale songs over 1,600 kilometres. See our page on ocean currents and migration.

Where exactly are cetaceans found in French waters?

The official marine environment assessment publishes 58 maps covering seven species, by season and by year, for the Atlantic, the English Channel and the western Mediterranean. See our interactive reading of the distribution of cetaceans in French waters.

Conservation and threats

Are cetaceans in danger?

Several species are threatened. The North Atlantic right whale numbers fewer than 400 individuals, the vaquita fewer than 10. The baiji is functionally extinct. See the IUCN conservation statuses and the population figures.

Do military sonars kill cetaceans?

Yes. Several mass strandings of beaked whales have been correlated with MFAS naval exercises. Necropsies: gas bubbles suggestive of decompression sickness. → Read the detailed answer

What is the impact of ocean noise on cetaceans?

Acoustic masking, behavioural disturbance, chronic stress, displacement of populations, strandings in extreme cases. → Read the detailed answer

Do microplastics affect cetaceans?

Yes. A blue whale is estimated to ingest ~10 million microplastics/day. Bioaccumulation and contamination by additives. → Read the detailed answer

Why is the vaquita on the brink of extinction?

It dies in the illegal nets set for the totoaba, a fish whose swim bladder is worth a fortune in China. Fewer than 10 individuals in 2024. → Read the detailed answer

Is the baiji really extinct?

Yes, functionally. No individual was found during the major 2006 expedition on the Yangtze. → Read the detailed answer

How many killer whales are left in the world?

About 50,000 worldwide, but several small populations are Critically Endangered (Southern Residents, the killer whales of Gibraltar). → Read the detailed answer

Do killer whales attack humans?

No fatal attack by a wild killer whale has been documented. The rare incidents involve killer whales in captivity. See the species page for the killer whale.

Why do whales strand?

The causes are many: disease, disorientation during storms, magnetic field anomalies, military sonar, bycatch, pursuit of prey into shallow water. See the causes of strandings.

What should I do if I see a stranded cetacean?

Alert the Réseau National Échouage (RNE) immediately. Do not try to put the animal back in the water on your own. See our full guide.

Do whales help to counter climate change?

They contribute to it. By feeding at depth and then fertilising the surface with their droppings, they boost the phytoplankton, which takes up CO₂ and produces half the oxygen of the planet: this is the “whale pump”. See our page on blue carbon.

Is keeping cetaceans in captivity still allowed?

Less and less. India has banned it since 2013, France has voted to end cetacean shows, and marine sanctuary projects are emerging. See our database of legislation and sanctuaries.

How many cetaceans does fishing kill accidentally?

A great many. About 8,000 common dolphins strand each winter on the French Atlantic seaboard, mostly victims of pelagic pair trawls. The vaquita of Mexico is down to about ten individuals. See our database of bycatch.

Are cetaceans protected by law?

Yes, by a web of instruments: CITES bans trade in the great whales, the International Whaling Commission moratorium has set commercial quotas at zero since 1986, and regional agreements such as ACCOBAMS or the Pelagos Sanctuary complete the framework. See our page on the international legal framework.

Does offshore wind threaten marine mammals?

The question arises area by area. Cerema has published a sensitivity index grid cell by grid cell across all French waters. Beware of the misreading: this index does not say where the animals are, but where a development would cut across their interests most. See our offshore wind sensitivity map.

Does sea level rise concern cetaceans?

Not directly for a pelagic species, but it measures the heat stored by the ocean, the very heat that moves the prey. Thirty-three years of satellite altimetry give a rise of 11.4 cm, and the Bay of Biscay is rising 30% faster than the global mean. See our page on sea level rise.

Evolution and etymology

What is the land ancestor of the cetaceans?

Pakicetus, an amphibious mammal of ~50 Ma. Cetaceans descend from the artiodactyls and their closest living relative is the hippopotamus. → Read the detailed answer

Why is the killer whale also called “épaulard” in French?

From an Old French word evoking a sword blade, in reference to the tall dorsal fin of the male. “Orque” comes from the Latin Orcus. → Read the detailed answer

How many fossil cetacean species are known?

The transition from the land to the sea played out over 10 million years in the Eocene, between 55 and 45 million years ago. See our gallery of ten key fossils, from the modest Pakicetus to the gigantic Livyatan.

Are there hybrids between cetacean species?

Yes, in captivity and in the wild alike. Wholphins, crosses between a false killer whale and a common bottlenose dolphin, have been born in tanks; the famous 52 Hz whale is probably a hybrid of a blue whale and a fin whale. See our overview of documented hybridisations.

Records and curiosities

What is the longest tooth of any cetacean?

That of the male narwhal: its “tusk” is a left upper canine that grows in a spiral and can reach 3 metres long. It is the only cetacean to show this trait. See the species page for the narwhal.

What becomes of a whale that dies on the ocean floor?

Its carcass sometimes sinks to 4,000 metres and sets off a whale fall: several tens of tonnes of organic matter in an abyssal desert, feeding a whole ecosystem for decades. See our page on whale falls.

Going further

Whale, sperm whale, dolphin: the difference How do you identify a cetacean? Cetacean glossary Cetacean sound library The cetacean records Test your knowledge