To celebrate our latest dolphin issue, we’re giving you a whopping 29 facts about dolphins you can use to impress your friends
1. Dolphins use tools
Using tools to solve problems is a sign of exceptional intelligence and dolphins have been discovered to use tools to find food or even just entertain themselves. Off western Australia, bottlenose dolphins cushion their beaks with sponges to stop them getting scratched or stung when foraging in the rocky seabed. Researchers were puzzled that dolphins were digging around between rocks rather than finding buried prey with their incredible echolocation. After looking closer, it was found that the kind of fish they were searching for beneath the seabed didn’t have air-filled swim bladders and weren’t easily detectable on the dolphin’s sonar system. They found a solution to this problem and even brought in a tool to keep their noses clean.
2. There are 32 oceanic dolphin species and five dolphins that live in rivers. They are all intelligent carnivores that use echolocation to hunt, communicate and navigate.
3. They feel emotion
Relative to their body size, dolphins have extremely big brains. The only animals with brains that are proportionally larger are humans and it has been suggested that dolphins are the second most intelligent animals on the planet. Brain size is a good clue as to how clever animals are, but it isn’t the only indicator of intelligence.
The area of a dolphin’s brain that is responsible for problem solving and self-awareness – the neocortex – has a bigger surface area and is more complicated than the same area in a human brain. It has also been discovered that dolphin brains have thousands of special neurons called spindle cells that are linked to emotional intelligence. These were thought to only exist in primate brains, but have recently been found in elephants, whales and dolphins. Dolphin experts think that this allows dolphins to feel complex emotions and have noticed that dolphins even seem to have a sense of humour! Dolphins show joy, empathy, self-control and they even mourn the dead.
Dolphin researchers have compared the learning ability of dolphins to the development of human children and some have given dolphins the label ‘non-human persons’. As dolphins live in close groups it’s important for them to be able to let others know how they are feeling, and to recognise emotion in others. Dolphin communication revolves around sound and the noises dolphins make are likely to contain complex information.
4. Dolphins recognise long-lost friends
Dolphins experience memories just like humans and long-term memory helps animals recognise a relative, friend or an unfriendly animal to be avoided. As dolphins have such complex social interactions they get to know one another quite well and remain friends for life. They form ‘fission-fusion’ societies that are constantly changing. This means that smaller groups break off and then fuse with other groups to form large pods. Living like this makes it essential for dolphins to be able to instantly recognise others and form memories of other dolphins.
The long-term memory of a dolphin has been found to last an astounding 20 years, if not longer. Studies have shown that dolphins remember each other for over 20 years without the memory decaying and even without the two dolphins meeting again. The duration of their first meeting is irrelevant, so even brief meetings are enough for dolphins to form life-long memories. This means that if two groups of dolphins meet they can remember what the others are like and they can choose whether or not to team up.
5. If a dolphin wants to peek above the ocean’s surface it ‘spy hops’, by quickly popping its head above the water to have a sneaky look around.
6. Dolphins can form pods of several thousands. The biggest pod ever spotted was off Dana point, California and was reportedly 11 kilometres (7 miles) wide!
7. Dolphins are born with a moustache
Dolphin calves are born with a hairy upper lip! Dolphins are mammals whose ancestors lived on land millions of years ago and the hair on the beak of a dolphin calf is a trace of their furry ancestry. Female dolphins have two tiny mammary slits on their undersides where milk is produced and whiskers on the dolphin’s beak help the calf find these mammary slits, but drinking under water isn’t easy.
When a dolphin calf is hungry it taps the mother’s mammary glands with its head and curls up its tongue into a straw to stop itself accidentally gulping down a mouthful of salty seawater.
Feeding is over in a flash to stop mothers with young from slowing down the group and some mothers have shaved feeding time down to just ten seconds! The calf’s moustache falls out a few days after birth, but leaves tiny black spots along the dolphin’s beak that are retained for life. Looking closely at a dolphin’s beak will reveal lines of dots where their baby hair once sprouted.
8. They lose a layer of skin cells every two hours
Dolphins constantly replace their outer skin cell layer and this cell loss helps wounds heal quickly and even helps combat skin parasites. Dolphins need to be streamlined to swim fast without resistance so their torpedo-like shape and hairless body help them glide through the water. To stay as smooth as possible, the top layer of a dolphin’s skin is extremely thin and every two hours they shed an entire layer of skin cells. They can rub against other dolphins or the sea bed, or even leap up and slam against the water’s surface to accelerate this process.
9.The deepest recorded dive for a dolphin is 300 metres (990 feet) and although dolphins usually breathe every few minutes, they can hold their breath for over 20 minutes.
10. Dolphins use social networks
Dolphins build up enormous networks of friends without going near a computer. Groups of dolphins can stay in touch and rely on fast transfers of information to survive. This kind of communication has been termed ‘social networking’ by scientists and has been compared to the internet, because dolphins can still transfer information even if individual dolphins are removed from the group. The basic idea is that a dolphin knows hundreds of other dolphins through association and can easily contact friends of friends through dolphins it is close to.
Dolphins use sound to communicate and have excellent memories, so they have a mental ‘friend list’ they can contact easily. Dolphins live in fluid groups that are constantly splitting up and merging with other groups, so they can meet hundreds of others on a daily basis. Their social networking abilities have arisen to help share news and keep in contact.
11. Dolphins see 360o
Dolphins have perfect panoramic vision both above and below the water. Their eyes move independently, like those of a chameleon, meaning they can look in two directions at once. This is one of their secrets to their amazing hunting abilities as well as helping them keep an eye out for predators.
12. Dolphins lack the jaw muscles needed to chew so they swallow fish completely whole and fish bones are broken down by powerful stomach enzymes.
13. Males and females have different roles
Male and female dolphins don’t look different and while all dolphins need to hunt and avoid predators, each gender has different responsibilities. Female dolphins often live with their relatives and have the responsibility of caring for and protecting the young. Female calves become mature at the age of five, but may spend years with their families. Young female dolphins are known to ‘babysit’ calves while the older females leave to hunt and mother and calf are reunited when she returns. Male calves become mature at the age of ten and will then leave the family group to team up with other adult males.
Male dolphins often join bachelor groups and form strong alliances that help them work together to hunt and breed. A group of males will swim close to an attractive female to guard her from other potential suitors, but if they do encounter rivals these dolphin gangs fight in front of the female. Males are thought to perform aerial leaps and underwater spins to impress their partners before mating begins.
14. In social interactions dolphins scratch one another with their teeth creating long parallel scars called ‘rake marks’ that heal very quickly.
15. Dolphins have powerful blocks of muscles called the peduncle in their tails that help them jump over five metres (15 feet) high!
16. They risk their lives to hunt
Dolphins are highly intelligent, excellent at solving problems and very quick to learn, so they are constantly finding new ways to catch their fish. They often cooperate in carefully planned formation and some strategies are incredibly risky. Many different dolphin species have learned a technique called ‘beach hunting’, where dolphins swim in synchronised lines to drive fish toward steep riverbanks or beaches. The fish have no choice but to try and escape by swimming towards the land, but the team of dolphins doesn’t give up.
These streamlined mammals approach the land at speed to force their bodies up on land, where the exhausted fish are trapped. The dolphins take their fill of the fish, then slide back down to the water. This is dangerous for the dolphins because although they breathe air, extended periods out of water can prove fatal.
17. To protect their eyes from friction when swimming fast dolphins have a sticky film over each eye called a dolphin tear.
18. All the sounds a dolphin makes come from the blowhole
Dolphins don’t have vocal chords and as much as it might look like the sound is coming from the mouth, it’s actually coming from the blowhole. The blowhole is essentially the dolphin’s nose and it is made of strong muscle to stop it opening under water. By manipulating this tight muscle and controlling how much air is released, the dolphin produces its characteristic sounds. These sounds can be clicks, buzzes or whistles and can be high or low pitched. Each sound delivers different information but scientists still don’t know the exact meaning behind this immense range of sounds.
19. Dolphins once walked on land
Dolphins have two tiny pelvic bones on each side of their bodies, which are remnants of their four-legged ancestry. Around 50 million years ago, land mammals that resembled small dogs began to take advantage of the food source available in the sea. Over millions of years these animals developed tail flukes to propel them through the water, lost their hair and eventually lost their back legs as they no longer needed them. A modern day dolphin’s spine extends to the tail flukes, but the flukes have no bones and are made from cartilage.
20. Dolphins eat up to ten percent of their body weight every day, which equates to 10-23 kilograms (22-50 pounds).
21. Dolphin pregnancy lasts 12 months, and calves are born tail first. The mother then nudges the newborn to the surface to teach it how to breathe.
22. They recognise themselves in a mirror
Mirror self recognition (MSR) is a sign of self-awareness and high intelligence, and researchers found that dolphins are able to recognise their mirror image. Researchers submerged a mirror in the dolphins’ pool and used waterproof ink to mark various places on the dolphins’ bodies. After being marked the dolphins rushed straight to the mirror to look at their ink marks. Some dolphins were ‘sham’ marked with water-filled markers, and if the dolphin couldn’t see a mark it simply swam away.
23. Dolphins help humans fish
In Laguna, Brazil, a group of dolphins has teamed up with local fishermen to catch mullet! The dolphins drive the silver fish towards the beach, where the fishermen wait on raised platforms with their nets poised. When the fish are in the shallow water, the dolphins give the fishermen a signal to let them know when to throw their nets. Not only do the fishermen get a consistent good catch, but the dolphins get to feast on fish that try to escape!
24. Dolphins have x-ray vision
Using their sonar systems dolphins can see beneath the sea bed and even through a human body! Dolphins can detect human pregnancy by emitting sound waves that bounce off objects in front of them, which allows them to see a growing foetus through the skin of the mother.
25. Dolphins have hands! The pectoral fins on each side of a dolphin contain five long fingers similar to a human hand.
26. Because dolphins constantly need to surface to breathe, they sleep one half of their brain at a time to stay alert around the clock.
27. They have teeth like reptiles
Most mammals have teeth of different shapes, but dolphins are unique in having teeth of all the same shape and size. Though this kind of dentition is usually seen in reptiles, dolphins have between 80 and 100 sharp conical teeth in long rows along their upper and lower jaws.
28. Some dolphins don’t need sight
The Indus river dolphin lives in such murky water that over time it has completely lost its sight, and it relies solely on echolocation to hunt prawns, catfish and carp. These dolphins often swim on their sides, which may be an aid to their use of sonar.
29. They can survive puffer fish poison
Dolphins have found a way to play with puffer fish without succumbing to its deadly venom. The puffer fish is the master of repelling predators with its ability to inflate and its potent toxin that has been known to kill humans. However, dolphins can chew on a puffer without getting a scratch.
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Image from https://www.flickr.com/photos/stevedunleavy/5591147154/