You don’t have to search the galaxy to find non-human intelligent life — increasingly we’re discovering it’s right here on Earth.

Several studies in the past decades have shown that many creatures — from octopuses to crows — are far cleverer than many people previously assumed.

This week, researchers reported that parrots have far more brain cells than apes — despite having much smaller brains.

Several studies in the past decades have shown that many creatures — from octopuses to crows — are far cleverer than many people previously assumed. But which is the brightest?

And last night, millions of viewers were moved by a documentary about Koko, a gorilla who communicates to people in sign language using a vocabulary of 1,000 words.

Increasingly, it seems the qualities that make human beings special — intelligence, communication skills and the ability to make and use tools — are not so special after all.

Of course, comparing human and animal brains is fraught with difficulties because there are so many types of intelligence.

For example, a squirrel might be able to recall the location of thousands of buried nuts six months after it hides them, but it would struggle to remember a human face.

Equally, a dog might be able to recognise its owner by scent, but isn’t going to be able to master email any time soon.

Inevitably, when comparing intelligence across the animal world, scientists focus on the kind of abilities that we are good at — making tools, using symbols for words, empathy and problem-solving.

So, based on these very human measures of intelligence, which animals are the smartest?

Orangutans are very clever. One of the brightest used to get out of chores by saying he needed the toilet

Orangutans hate chores

The most intelligent animals tend to be social animals like us — and orangutans are no exception.

These endangered apes are some of the brainiest creatures on earth and are as bright as a four-year-old child.

In the wild, they use stick tools to try to spear fish, measure the depth of water and get hard-to-reach food. In captivity, they are superb mimics — and have learnt to use hammers, cool themselves with damp rags and wash clothes.

One of the smartest was Chantek, a cheeky ape raised by humans in the Seventies. By nine months he had picked up enough sign language to ask U.S. scientists ‘give me drink’. By four he had made up the phrase ‘tomato-toothpaste’ to describe ketchup.

He even learned to lie and would get out of boring chores by announcing he needed a toilet break.

Dolphins enjoy their leisure time by playing ‘catch’ with turtles and even enjoy sliding down the heads of humpback whales

Dolphins play catch

Their playfulness and intelligence is legendary. And they pass on new skills to others.

When Billie the dolphin spent three weeks in captivity in Australia, she learned to walk backwards through the water on her tail. Back in the wild, she passed on the trick to wild dolphins who started doing it for fun.

Dolphins use sea sponges held in the mouths as tools to disturb food on the sea bed and shells to gather fish. They play ‘catch’ with turtles and even enjoy sliding down the heads of humpback whales.

They can also be deceptive. When a captive dolphin called Kelly, of the Institute for Marine Mammal Studies in Mississippi, was trained to bring scraps of paper to her keeper in exchange for a fish, she devised a way to get more food.

When she found a scrap, she tore it up, hid the pieces under a stone and brought them up one at a time.

Animal behaviour experts believe crows are as smart as the average seven-year-old human

Plenty to crow about

There’s nothing bird-brained about crows, a family that includes ravens, jackdaws and rooks.

Animal behaviour experts believe they are as smart as the average seven-year-old human and as clever as a great ape.

The brainiest is the New Caledonian crow, a native of the Pacific islands. In lab tests, they have worked out they can raise the water level of a tube to get floating food by dropping in pebbles — but not pieces of sponge.

The most famous crow is Betty, based at Oxford University.

When she was given a plastic clear tube with a tiny bucket of food at the bottom she picked up a wire, bent it into a hook and used it to fish out the bucket. Those sorts of logical skills are extraordinary.

Smartness comes in all forms. Betty’s cage mate, Abel, never bothered making hooks — he preferred to wait until Betty brought up the bucket and would then bully her into handing over the food.

Other crows are equally clever. In Japan, crows place nuts on the road at junctions and wait for car wheels to crush their shells.

Chimps have brilliant memories, work as a team to hunt, care for their sick and mourn their dead

Why chimps are champs

Chimps and their cousins bonobos care for their sick, mourn their dead and work as a team to hunt.

They use sticks as tools to fish bugs out of cracks, and use rocks as nutcrackers.

One of the smartest is Kanzi, a bonobo at an ape centre in Iowa.

He points to symbols on a board to communicate more than 200 words. On a day out, he touched the symbols for marshmallow and fire — and when given matches and wood, made a fire, lit it and began to toast the sweets.

Chimps have brilliant memories, too. This month, a documentary showed former lab chimps Swing and Doll being reunited with the woman who’d rescued them in the Seventies.

The apes hadn’t seen Linda Koebner for 18 years — yet when they came face to face, they were overjoyed and showered her with cuddles.

Elephant empathy is astounding, but so is their sneakiness. Working Asian elephants are sometimes given bells so they can’t sneak into farms at night. But some block the bells with mud so they don’t make a sound

Elephants are sneaky

Elephants have the largest brains of any land animal. They are as good as chimps at recognising themselves in mirrors, problem-solving and using tools. In the wild, they use sticks to scratch themselves, and leaves to swat flies.

And their empathy is astonishing. Elephants will flinch if a family member reaches out to touch an electric wire with a trunk.

Mothers guard dead young for days, while groups slow down when they approach elephant skeletons, and spend time stroking the bones.

Working Asian elephants are sometimes given wooden bells so they can’t sneak into farms at night. But some block the bells with mud so they don’t make a sound, allowing them to silently raid banana plantations.

Parrots are known for their ability mimic, but are also very skilled when it comes to solving problems

Slick as a parrot

Parrots aren’t just excellent mimics, they are superb at solving problems too. The most famous grey parrot was Alex, who could say more than 100 words, identify 50 different objects, count up to six out loud, distinguish between seven colours and five shapes and understood the meaning of ‘bigger, smaller’ and ‘same and different’.

His last words before he died, aged 31, in 2007 to psychologist Irene Pepperberg were: ‘you be good, see you tomorrow. I love you.’

Some studies show gorillas can recognise themselves in mirrors — a test that shows whether an animal is aware that they exist in the world

Gorillas love mirrors

They may be less curious and less excitable than chimps, but gorillas still have a keen intelligence and the ability to learn sign language.

The most famous gorilla, Koko has mastered more than 1,000 words and signs in sentences, tells jokes and invents words — coming up with the phrase ‘finger bracelet’ for ring.

Some studies show gorillas can recognise themselves in mirrors — a test that shows whether an animal is aware that they exist in the world.

Pigs are far brighter than horses, cows or chickens and find completing mazes a doddle

Pigs enjoy a puzzle

Without question, pigs are the brain boxes of the farmyard and are far brighter than horses, cows or chickens. They have brilliant long-term memories and find mazes a doddle. Scientists have even trained them to use joysticks to move a cursor around a computer screen and they can learn tricks — from opening cage doors to jumping through hoops.

Pigs are also cunning. If one believes another pig is heading out for a spot of lunch, it follows, hoping to get a share. But if a pig thinks it is being followed, it will deliberately lead the rival away from the food until it has shaken it off.

Earlier this year, a German pig called Moritz was filmed by its owner completing a jigsaw puzzle using its mouth to place the pig-shaped pieces.

Octopuses are brilliant at underwater mazes and will unscrew childproof bottles with ease

The Houdini octopus

Octopuses are so bright that keeping them in aquariums can be a problem. In April, workers at the National Aquarium of New Zealand discovered that Inky the octopus had snuck through a gap in its tank overnight scampered 8 ft across the floor and slithered down a 160 ft drain to the sea.

Octopuses are brilliant at underwater mazes and will unscrew childproof bottles with ease.

And they are playful. At Seattle Aquarium, an octopus was put in an empty tank with a floating bottle. After a few minutes, it blew a jet of water at the bottle, nudging it away. The bottle floated to a water jet in the tank which pushed it back to the octopus.

The animal repeated the move 20 times — just like bored humans might bounce a ball against a wall.

The average dog understands around 160 words and its own name — roughly the same as a child of two

Man’s cleverest friend

Dogs are extraordinarily good at understanding their masters. They can read human expressions and if an owner looks at something, a dog will follow the gaze.

The brightest dog in the world is thought to be Chaser, a border collie from South Carolina, who can identify more than 1,000 toys by their name and fetch them when asked. She understands dozens of verbs — including ‘take it’ and ‘paw it’ — and can distinguish between 800 cloth animals, 116 balls and more than 100 plastic toys.