Humans aren't the only intelligent creatures on Earth. As National Geographic points out, research proves that animals are much smarter than people realize. With that in mind meet nine of the planet's cleverest creatures.

1. Ravens

An Australian raven perched on a railAn Australian raven perched on a rail. (Photo: DickDaniels/Wikimedia Commons)

Ravens are more than the subject of dark themes by writer Edgar Allen Poe. They are also extremely resourceful animals that have been known to multi-task. Researchers from Canada and Scotland have shown that ravens use logic to understand their surroundings in a way that may surpass the ability of the great apes. The crow, a close cousin to the raven, is also an extremely smart bird.

2. Dolphins

dolphinsA pod of dolphins swim in the ocean. (Photo: Willyam Bradberry/Shutterstock)

Dolphins are well-documented as intelligent animals. As Discovery News reports, the dolphin’s large brain is structured for awareness and emotion. In fact, dolphin brains are more structurally complex than humans. As Emory University dolphin expert Lori Marino told Discovery News, "If human standards for intelligence are applied to non-human animals, however, dolphins come very close to our own brain aptitude levels."

3. Rats

Rats munch on some carrotsRats are much smarter than we humans often given them credit for. (Photo: Tambako The Jaguar/flickr)

Perceived as purveyors of disease, Rattus norvegicus have earned a bad reputation, but they are highly intelligent creatures. As researchers at the University of Guelph in Ontario point out, "Although rats may not approach cognitive tasks using strategies observed in human subjects, they are frequently successful on their own terms. Indeed, rats are adept at exploiting procedural loopholes and confounded variables overlooked by human test designers."

4. Pigs

Millions of pigs dying from virus Pigs are smart enough to outwit friends for food and can learn to perform various tricks. (Photo: janecat/Shutterstock)

Pigs may be the smartest domestic animals in the world. The New York Times reports on researchers who have found that domestic pigs can use mirrors to find their food, and will try to deceive other pigs so they can "hog" more food. They also learn quickly and can do tricks ranging from jumping through hoops to playing video games with joysticks.

5. Bonobos

BonobosLike some other chimps and apes, bonobos are capable of learning human sign languages to express themselves. (Photo: Psych USD/Wikimedia Commons)

The bonobo is a close cousin to the chimpanzee, another famously intelligent animal. Extremely endangered, the bonobo is found only in central Africa. Like other great apes, bonobos have been taught to use sign language and symbols. National Geographic writes of "the bonobo Kanzi, for instance, [who] carries his symbol-communication board with him so he can talk to his human researchers, and he has invented combinations of symbols to express his thoughts."

6. Squirrels

squirrel on branchSquirrels are social learners. (Photo: ehpien/flickr)

Anyone who has ever seen a squirrel dart across a crowded street has wondered if they are aware of the danger. It turns out they may be — but if there is food on the opposite end of the street, they may not care. Squirrels are fast learners, according to a recent study from Science Daily, and they learn from their peers. Stealing food is a trick that squirrels pass along.

7. Elephants

An elephant walks in the African savannaElephants will use tools and can be clever thieves. (Photo: Johan W. Elzenga/Shutterstock)

Elephants have a reputation for smarts. Elephants have been observed using tools such as sticks to pick at ticks or using palm fronds to swat at flies. As the Nature Institute points out, "many young elephants [in the wild] develop the naughty habit of plugging up the wooden bell they wear around their necks with good stodgy mud or clay so that the clappers cannot ring, in order to steal silently into a grove of cultivated bananas at night." The elephants will then gorge on the banana while the nearby farmer is none the wiser.

8. Cows

A herd of cows in AustraliaCows are not only smart animals; they're also very emotional. (Photo: Marc Dalmulder/flickr)

Cows seem like placid animals merely concerned with chewing their cud. As it turns out, they possess a rich and complex emotional life. The Times reports that scientists have found that cows have friends and enemies. Further, "Cows are also capable of feeling strong emotions such as pain, fear and even anxiety — they worry about the future."

9. Bees

A bumblebee sucking nectar on an echinacea purpurea flower headBees are smartest in groups, relying on swarm intelligence to get things done. (Photo: Alexandra Giese/Shutterstock)

Bees exhibit what experts call classic swarm intelligence. A single bee may not be smart in the classical sense, but a hive of bees is. As National Geographic reports, swarm intelligence works when no single creature sees "the big picture." Rather, each works on simple rules in one location. But what happens when bees disagree? It turns out that they can hold a democratic "dance-off" to make a hive decision.

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