At the top of the food chain, humans have long believed ourselves to be the brainiest life on the planet. But growing research shows we might have some competition—and that "intelligent" doesn't always mean what you think. Take our quiz to see how smart you are about the planet's cleverest critters.
Alex the African grey parrot knew more than 50 objects and the names of seven shapes and colors. When he died, his trainers brought a new bird named Griffin on board. Griffin eventually demonstrated intelligence levels and communication skills equivalent to those of a 3-year-old child.
Crows are some of the best puzzle solvers on the planet. The New Caledonian variety, considered the most intelligent of all birds, can not only solve puzzles, but can even fashion tools—without ever having used or seen the tools used previously.
"Elephants never forget" isn't far from the truth at all. There are documented accounts of some individuals remembering each other after more than three decades spent apart. Matriarchs in a group of elephants are also able to identify and keep track of up to 30 other members of the group.
Koko the gorilla famously understands around 2,000 words and can sign 1,000 words herself, according to her caretaker. Some scientists doubt these claims, however.
A 2006 study of an elephant named Happy revealed that these creatures can recognize themselves in the mirror. Aside from humans, apes and dolphins, no other living creatures are known to possess this level of self-awareness.
In 2010, a journal article presented a study of Chaser, another dog of the same breed that could identify more than 1,000 objects simply by hearing their names. Before Chase, another border collie named Rico made headlines when he showed researchers he knew around 200 words.
In a remarkable display of emotional intelligence, rats will release other rats from cages, even though the act poses no apparent immediate benefit for the cage opener. One hundred percent of female rats and 70 percent of male rats studied eventually opened cages for trapped rats, and many even shared food with their newly freed friends.
Around 82 percent of variation in primate intelligence can be explained by brain size and variety of diet. Eating a wider range of foods requires more intelligence, because it means the primate must learn to identify and find these foods in different places and seasons.
Presented with the numbers one through nine flashing randomly around a computer screen, chimps can instantly repeat the exact placement and sequence after the numbers disappear. In tests that pitted their performance against humans, even people known for their impressive memories, chimps still come out way ahead.
Bees perform an elaborate and precise movement to communicate. Known as a waggle dance, it reveals the distance and direction of good nectar sources to fellow hive members.
With their "vampire" name, these creatures may not strike you as particularly generous. However, because these bats die after 2 days without food, the females frequently share with other bats to keep everyone going in times of food scarcity. In fact, they also demonstrate high social intelligence by remembering who's shared with them in the past, showing that they're more likely to reciprocate to bats who have been generous to them. For what it's worth, male vampire bats never share their food.
There's really no limit to dolphin intelligence, and their ability to communicate with one another is well-established. Turns out, dolphins also know how to use tools to their advantage, wrapping sea sponges around their beaks (or snouts) to protect themselves from stings, bites, and claws while they search the sea floor for food.
In 2014 researchers discovered that a group of red deer living in the Czech Republic had learned not to cross an electric fence on the nearby German border—except the fence had been gone for two decades. The only explanation seemed to be that the deer had learned from one another that it wasn't safe to go there.
You know how humans use singsong voices and silly terms to communicate with babies? Turns out some animals do it, too. Songbirds and certain types of monkeys have both been shown to sing or communicate with their offspring more slowly, musically and repetitively than they do with other adult animals.
Cockatoos are amazing lock pickers. In one study, the birds could get through five different levels of locks -- slides, pins, latches, bolts and wheels -- in order to reach a delicious cashew locked inside. When scientists took the locks apart and reorganized them, the cockatoos figured out the new arrangement as well.
The Clark's nutcracker, a tiny bird weighing only a few ounces, hides anywhere from 5,000 to 100,000 seeds each year. The bird then triangulates the location of each seed based on nearby landmarks -- and uses that information to remember where most of the seeds are buried once winter hits.
Gila woodpeckers really can get their food "to go" by making a bowl out of tree bark for carrying honey home.
In the 1990s, a seven-year-old sea lion named Rio was said to demonstrate an understanding of, if A=B and B=C, then A=C (and, then, C=A). No joke: Rio learned to pair images of different objects, and then made the leap in logic between images that he hadn't seen or paired together before. Some researchers dismiss these results, but others believe more than just sea lions have this ability...Rio was just the first to be tested by animal behaviorists.
In a landmark 1959 study, researchers found that rats can learn to push a lever to earn food. Even more importantly, they will stop pushing the lever if they learn that by gaining food for themselves, they are delivering a powerful shock to another rat. This and similar studies suggest that rats possess a sense of empathy.
Repeated studies have shown that monkeys can not only count, but can also rank groups of items by size or quantity. Surprisingly, when the studies were replicated with pigeons, they performed just as well as the monkeys.
Dog intelligence tests suggest that canines can count and can do some simple math. For example, if an object is placed on a table, then a screen is lowered, then another object is placed behind the screen while a dog is watching, the dog expects to see two objects when the screen is raised. Tests show that dogs react differently if an object has been secretly removed or added before the screen is raised.
In some ways, scientists suspect that domestication made dogs dumber. In studies of wolves, the animals were found to understand numbers and counting better than domestic dogs. Perhaps being cared for in the home dulls your senses, while caring for yourself in the wild keeps the brain sharper.
The Japanese macaque, also called the snow monkey, has been seen dipping sweet potatoes into seawater. It's not entirely clear whether this is to wash the potatoes or make them saltier, but the custom apparently started with one individual before spreading across the colony as a learned behavior.
Chimps use rocks to crack nuts, and they use sticks for hunting or soaking up water to drink. While scientists have long thought that chimps only started using tools in the 19th century, recent discoveries have found primate tools dating back more than 4,000 years -- to the late Stone Age.
These mega lizards, like Komodo Dragons, have proven they can count to six in experiments using snails. Given six snails to eat, they will remember the number so that if they are given fewer snails the next time, they will continue searching for the missing quantity.
Dogs may have a reputation for being so much smarter than their feline counterparts, but studies show that the two species perform equally well on memory tests. Both cats and dogs have episodic memories, indicating self-awareness.
Every bottlenose dolphin has a unique whistle. The sound not only identifies the animal, very much like a name, but also provides clues to his location and even his state of mind.
A seal found in Maine, who was raised by a local couple, became famous when the media found out he could talk -- with a thick Maine accent. He appeared on TV and radio before dying at the age of 14. Videos of Hoover talking can be found online for skeptics who need a little convincing.
You may think of them as bird brains, but chickens actually recognize numbers and counting in a linear fashion, like humans. They know that bigger numbers go to the right and smaller numbers go towards the left when presented with a card featuring a number of dots, for instance.
The average dog can understand around 165 words -- about the same as a two-year-old child. By age three, most children have surpassed dogs, both in terms of vocabulary and one other skill that dogs simply can't grasp -- recognizing themselves in a mirror.
While crows and many other birds demonstrate remarkable social intelligence and problem-solving skills, it's starlings who are known as the most talented mimics and song virtuosos. One famously copied an unpublished tune that Mozart whistled in a pet store, convincing the composer to adopt it. In this case, a study of the Chomsky hierarchy in linguistics showed that starlings are able to insert 'words' and clauses within their 'sentences' to create new meanings: "The bird flew away" can become "The bird the cat chased flew away," etc. This ability to create theoretically infinite but grammatically correct and meaningful sentences was long thought to be strictly human domain.