Frequently Asked Questions about Facts about whales and dolphins

What are the differences between whales, dolphins and porpoises?

Collectively, whales, dolphins and porpoises are known as cetaceans. Cetacean species are divided into two groups;

(1) Baleen whales – these are the “great whales” and as their name suggests they all have baleen plates that are used to filter their food (which consists of plankton and small species of fish).

(2) Toothed whales (otherwise known as odontocetes and including all species of dolphin and porpoise) – which as you would expect, have teeth, and eat larger prey items, including at times, other marine mammals. The main differences with porpoises are that they are usually smaller than other toothed whales and instead of cone-shaped teeth they have flat, spade-shaped teeth.

As a general rule of thumb, baleen whales are larger and slower (except the fin whale which is known as the “greyhound of the sea”) than toothed whales.  Additionally, ALL baleen whales have two blowholes whereas toothed whales only have one.

Humpback whale
Humpback whale

(3) Difference between a dolphin and a porpoise.

The biggest difference is size, with all species of porpoise being that much smaller than their dolphin cousins. Porpoises don't have the pronounced beak that most, but not all dolphins have and they also have different shaped teeth. Porpoise teeth are spade-shaped whilst dolphins are conical.

Harbour porpoise © Charlie Phillips
Harbour porpoise © Charlie Phillips

A dolphin has a hooked or curved dorsal fin (except for those species that don't have a dorsal fin) whereas a porpoise has a more triangular dorsal fin, and generally speaking, dolphin bodies are leaner, although porpoises’ are a little more chunky. 

Dolphins are also more "talkative" than porpoises. The whistles made by dolphins are produced through their blowholes and although porpoises do not do this, possibly due to structural differences in the porpoise’s blowhole, they can still be pretty noisy as they "puff" the air out when they surface. 


Short-beaked common dolphin
Short-beaked common dolphin

Dolphins and porpoises also have many similarities, one of which is their extreme intelligence. As research evolves, it is likely that more (or perhaps fewer) differences between dolphins and porpoises will be revealed.

More facts about whales and dolphins or have a look in our whale and dolphin species guide.

How many species of whales, dolphins and porpoises are there?

There are currently 89 species of whales, dolphins and porpoises. This is composed of 14 species of mysticetes (otherwise known as baleen whales) and 75 species of odontocetes (otherwise known as toothed whales and includes all species of dolphin and porpoise). If however you were to include sub-species and sub-populations then that figure would rise to 118. 

Find out more in our species guide.

How do whales, dolphins and porpoises communicate with each other?

Communication amongst whales and dolphins is achieved in several ways. They create sounds, make physical contact and use body language. Large whales can communicate over huge distances (across entire ocean basins) using very low frequencies. Dolphins and porpoises however, usually use higher frequencies, which limits the distance their sounds can travel.

In general, dolphins make two kinds of sounds, “whistles” and “clicks”. Clicks are used to sense their surroundings through echolocation, while they use whistles to communicate with other members of their species and very likely, with other species too. It is also thought that each dolphin has a unique whistle called a ‘signature whistle’, which is used to identify an individual.

What are the different fins on a dolphin used for?

The tail fin, or fluke, is used for propulsion through the water.

The pectoral fins (on each side) provide directional control and the dorsal fin (in those species that have one) provides stability whilst swimming.

Many individuals however have been documented without a “complete set” of fins (likely as a result of incidental entanglement in fishing gear, being hit by a boat’s propeller or a lucky escape from a predator) and therefore they can sometimes adapt quite well to losing part or all of a fin.

Dolphin illustration
Dolphin illustration

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What is echolocation?

Dolphins and other toothed whales use a sense called echolocation to navigate and hunt underwater, in addition to having extremely good eyesight (except the river dolphins who are bordering on being blind). They emit clicks and use a part of their body called the melon to focus these sound waves on objects around them. Using special cavities in their jaws, they then detect and interpret the echoes that bounce back off. This allows them to build up a picture of their surroundings and can help in locating prey, for instance when it might be hiding under the sand. 

Sperm whales also use echolocation to find their way around the dark depths of the ocean and to help with hunting for squid. Though only very brief, the clicks they make are the loudest sound in the animal kingdom.

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Illustration showing how dolphin echolocation works.

How do whales, dolphins and porpoises hear?

Whales do not have ears on the outsides of their heads. Instead, they generally hear sounds through special structures in their jawbones.

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Do whales, dolphins and porpoises have a sense of smell?

No – they lack an olfactory nerve and associated lobes and therefore it is believed that they have no sense of smell. They do however have a keen sense of taste, showing a preference for specific types of fish and seafood.

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What do dolphins eat?

Dolphins are carnivores; they eat other animals. Dolphins eat a variety of fish, squid, shrimps, jellyfish and octopuses. The types of fish and other creatures dolphins eat depends on the species of dolphin, where the dolphins live and the wildlife that shares their habitats.>

There are more than forty species of dolphin and they live in environments ranging from fresh water rivers, estuaries, coastal waters to deep sea open oceans. Most dolphins are opportunistic feeders, which means they eat the fish and other animals sharing their homes.  All dolphins eat fish and those living in deep oceans also eat squid and jellyfish.

Bottlenose dolphins are found worldwide in temperate and tropical seas and the types of fish they eat, is dependent on where they live and what time of year it is. Bottlenose dolphins living in the Moray Firth, Scotland, favour salmon when it is available in the spring and summer months. In the winter, salmon is scarce, and so they eat herring and mackerel. Bottlenose dolphins living elsewhere eat their favoured local fish which can be mullet, mackerel, catfish and more tropical species of fish. All dolphins have teeth but they don't chew their food, they just, grab, bite and swallow!

Amazon river dolphins are known to eat more than 40 different species of fresh water fish and they also eat fresh water crustaceans. Spinner dolphins eat fish, jellyfish and krill. Dusky dolphins eat shrimp, squid and various fish, including tiny anchovies. Rough-toothed dolphins live in deep water oceans and eat mostly squid. Commerson’s dolphins feed on small fish, crabs, octopus, and small crustaceans in kelp beds close to shore and near the seabed. New Zealand dolphins feed on species of small fish and squid in shallow coastal waters.

Orcas are the biggest members of the dolphin family; resident orcas in Northern British Columbia, Canada eat only fish – their favourite is salmon. Other orcas specialise in eating much bigger prey including seabirds and mammals such as sea lions, dolphins and whales. Orca diet depends on what food is available to them where they live and what techniques they have learnt from their elders to hunt their food.

Dolphins hunt using their highly-developed echolocation, which means they can find food no matter how murky the water might be. Not only that but they can even use it to identify any prey that might be hiding, such as under the sand!

What do dolphins drink?

Dolphins get all the water they need directly from the food they eat. Their main prey (fish and squid) contains large amounts of water. Dolphins don’t lose water by sweating, like we do, and so they need less water than us in their diets.

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Bottlenose dolphin Zephyr with salmon
Bottlenose dolphin Zephyr with salmon

How do dolphins sleep?

Dolphins sleep in a very different way to the way we humans do.  Humans have prolonged periods of unconscious sleep and we are not aware of  our surroundings for periods of time while sleeping. Humans have a breathing reflex and when we sleep or become unconscious, we continue to breath automatically.

Dolphins cannot sleep in this way, they have to remain conscious, even when they are sleeping. This is because their breathing is not automatic, it is consciously controlled. In other words dolphins have to actively decide when to breath, and so they must be continually conscious to breath. If like us, dolphins went into a deep unconscious sleep, they would stop breathing and suffocate or drown.

To get around this, dolphins only allow one half of their brains to sleep at a time; the other half stays alert to enable the dolphin to continue breathing and look out for dangers in the environment. Dolphins only close one eye when they sleep; the left eye will be closed when the right half of the brain sleeps, and vice versa. This type of sleep is known as unihemispheric sleep as only one brain hemisphere sleeps at a time. Dolphins alternate which side is sleeping periodically so that they can get the rest they need without ever losing consciousness. 

When sleeping, dolphins often rest motionless at the surface of the water, breathing regularly or they may swim very slowly and steadily, close to the surface. In shallow water, dolphins sometimes sleep on the seabed rising regularly to the surface to breath.

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Atlantic white-sided dolphin
Atlantic white-sided dolphin

Do whales and dolphins sneeze?

No - A whale or dolphin already exhales far faster than humans and other land mammals do. A human sneeze is about 100 mph ... whales are even faster than that at their normal breathing rate ... so it's possible that they have no "need" for sneezing in the traditional sense.

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Do whales, dolphins and porpoises have hair?

All mammals have hair at some point in their life and cetaceans are no exception. Although lost before or shortly after birth, tiny hairs are found around the tip of the rostrum. The only exception to this is the boto, which doesn’t lose these hairs and maintains them throughout its life.

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What is baleen?

Baleen is made out of keratin, the same protein that makes up our fingernails and hair. A baleen whale, such as the humpback whale below, has about 600 baleen plates in its upper jaw, which act like a strainer as it feeds. Like humans, whales cannot drink saltwater. Hairs on the baleen plates catch the fish or plankton, while the saltwater washes through and goes back into the ocean. Some whales eat about one ton (2,000 lbs.) of fish each day.  You can tell if you see a baleen whale by their blowholes. All baleen whales have two blowholes visible on the top of their heads.

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Baleen in mouth of humpback whale

How do dolphins breathe?

Dolphins are mammals and breathe air into their lungs, just like we do. Dolphins cannot breathe under water like fish can as they do not have gills. Dolphins breathe through a nostril, called a blowhole, located right on top of their heads. This allows them to take breaths by exposing just the top of their heads to the air while they are swimming or resting under the water. After each breath, the blowhole is sealed tightly by strong muscles that surround it, so that water cannot get into the dolphin’s lungs.

When a dolphin surfaces for air, he breathes out (exhales) first and then breathes in (inhales) fresh air; it only takes a fraction of a second for the dolphin to do this.  If you are close by, it is easy to hear a dolphin’s ‘blow’ at the surface; in fact you will often hear a dolphin before you see him!  The blow is the sound you hear, and the spray of water you see, when the dolphin forcefully breathes out and clears away any water resting on top of his blowhole.  The water spray is not coming from the dolphin’s lungs; it is just water sitting on top of its head around the blowhole being blown away before he inhales.

Dolphins do not breathe through their mouths in the same way as people can, they only breathe through their blowholes. In this way, breathing and eating are kept entirely separate in dolphins so that they can capture prey in their mouths and swallow it without the risk water getting into their lungs. However, in 2016 a paper was published that reported on a dolphin that had learnt to breathe through its mouth.

Dolphins are able to hold their breath for several minutes but typically they breathe about 4 or 5 times every minute.

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Bottlenose dolphin at surface
Bottlenose dolphin at surface