Original photo by Rudney Uezu/ Unsplash

Humans may be considered the most intelligent animals on Earth, but other species are not far behind. Scientists measure animal intelligence by looking at an animal’s self-awareness, self-control, and memory, all of which influence how well a creature processes information and solves problems. Judging an animal’s smarts is still a gray area, however. It’s pretty difficult to get a large number of wild animals together for a controlled behavioral experiment, and sometimes the tests scientists devise to judge a species’ intelligence don’t jive with the way animals perceive things. But the species included here have consistently impressed us with their smarts.

View of an African gray on a tree branch.
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African Gray Parrots

African grays are the chattiest of all the parrots, but their skills go beyond mimicry. They can actually associate meaning with the human sounds they make; one bird named Alex could count to six in English, correctly identify five shapes and seven colors, and differentiate objects by material, color, and more. To top it all off, he’d correct other parrots in the lab in English as they tried to do the same — and loved commanding humans, too. Separate studies have found that African gray parrots have excellent deductive reasoning and teamwork skills.

A couple of loving and colorful pigeons mating.
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Pigeons

Pigeons are wildly misunderstood birds, and they’ve only been considered a nuisance for the last century or so. The ordinary city pigeon is actually a feral descendant of domesticated pigeons that humans no longer had a use for, and the city birds eventually developed a reputation as unsanitary. But their navigational abilities are unparalleled — you’ve probably heard of a homing or messenger pigeon — and, like corvids, they can recognize faces. Recent research has shown that they learn in a method similar to an artificial intelligence model, and after some training are able to recognize patterns and make decisions.

Bonobo standing waist-deep in water.
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Bonobos

Bonobos are similar to chimpanzees in that they’re both very closely related to humans and highly intelligent. While chimps are better at solving physical problems and using tools, bonobos are more socially intelligent and better at solving tasks that require theory of mind — a human developmental step that enables seeing things from another’s point of view. Bonobos are also notable for their generally peaceful societies that resolve conflicts more often through sex than violence.

Don breed horse running on the field.
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Horses

Horses are great learners and can communicate with human beings through symbols. In one study, horses were able to express whether or not they wanted a blanket on by nudging a board with relevant icons. In another, they were able to determine whether or not a human attendant knew where a carrot was hidden — if they didn’t, they would attempt to guide the human toward it using visual and tactile signals, like touching them or lightly pushing them.

One famous horse, Clever Hans, probably couldn’t do arithmetic, read, or spell, as his owner claimed he could. But he did, inadvertently, demonstrate the ways that horses are smart — it turned out he appeared to have more advanced knowledge because he was picking up on subtle, possibly unconscious cues from his owner.

Common raccoon in mangrove forest.
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Raccoons

Unlike many species, raccoons have thrived as humans have expanded into their habitat. They’re both highly adaptable and extremely clever. One experiment showed that raccoons could use water displacement to gain access to a marshmallow that was floating too low for them to grab. Other research as far back as 1913 showed that raccoons were able to identify a specific light source even after getting distracted — something that rats and dogs in the same study could not.

A school of gray dolphins in the ocean.
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Dolphins

Dolphins have one of the largest brains relative to body mass in the animal kingdom, which is thought to be partly responsible for the mammals’ highly developed intellect. Captive dolphins are taught tricks, have been trained to detect underwater explosives, and have even starred in TV sitcoms. They can also recognize themselves in a mirror, a basic test of self-awareness that indicates intelligence. Wild dolphins have been observed using tools, hunting cooperatively, and communicating in a variety of squeaks, squawks, and whistles, all pointing to dolphins’ cognition.

A close-up of a black raven sitting atop an outdoor landscape.
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Ravens

In some Native American folklore, ravens are known as tricksters — a reputation that may stem from these birds’ intelligence. Ravens and their relatives in the family Corvidae, which include crows and jays, have the same brain-to-body-size ratio as apes, suggesting a high level of cognition. Ravens are known for their complex social behaviors, such as holding apparent grudges against people who cheat them (a sign of their memory) and enacting “funerals” over dead members of their species, from which they pick up social information. They even recognize human faces. Corvids also understand cause and effect, plan for the future, and make and use tools, like fashioning sticks to help them extract food from tight spaces.

Two black chimpanzees turning and looking at the camera.
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Chimpanzees

Jane Goodall’s observations of chimpanzees using blades of grass to tease tasty termites out of their mound revolutionized our views of animal intelligence. And since her discovery in 1960, chimps have shown that their cognitive abilities rank pretty close to our own. In addition to the grass, chimps create special tools from leaves, twigs, and tree branches for different tasks. They also throw rocks at trees, perhaps to communicate to other chimps across a large area, and crack open nuts against anvil-like stones. Recently, scientists observed wild chimpanzees applying squashed insects to wounds as a form of self-medication. In addition, chimps interact with complex vocalizations and gestures and have even learned to “speak” with trainers in rudimentary pictorial or sign languages.

A close-up of a pig looking up at the camera.
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Pigs

Pigs’ intelligence hasn’t been studied as thoroughly as that of primates, rodents, and birds, but analyses suggest that their performance on some psychological tests is on par with dolphins. A 2009 study found that seven out of eight pigs could process reflections of objects in a mirror and use the information to find food hidden behind a wall. Pigs can discern objects based on different characteristics and remember their choices over time, which demonstrates long-term memory. They can also prioritize which memories are important, like how to access desired food when presented with different options. Anecdotally, pigs have appeared to show empathy for humans, such as when naturalist Sy Montgomery’s normally active 750-pound porker, Christopher Hogwood, became quiet and docile while Montgomery grieved the loss of loved ones.

A close-up of an Octopus vulgaris.
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Octopuses

What octopuses lack in exoskeletons, they make up for in brains. These eight-armed cephalopods not only have the biggest brain-to-body-size ratio among invertebrates, but they also have multiple brains — a central neurological organ and one “mini-brain” in each arm. Octopuses can perceive and react to information quickly — by suddenly changing their color and pattern to camouflage themselves, for example — which suggests superior cognitive abilities. They’re famous for getting into and out of tight spaces, unscrewing jar lids, manipulating objects to solve puzzles, stealing crabs out of fishermen’s traps, and even escaping their aquarium tanks. A 2010 study of eight giant Pacific octopuses found that they could even recognize individual people.

Two elephants in an open field in the wilderness.
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Elephants

Elephants are famed for their excellent long-term memory, a key indicator of animal intelligence. They can also solve practical problems. In a famous 2010 study, Kandula the Asian elephant figured out how to reach food on a high branch by pushing objects, like a large plastic cube, under the food and then using the cube as a step stool. Another well-known experiment found that elephants can grasp the need for cooperation and alter their behavior to achieve a shared goal. Observations of elephant social groups over decades have revealed tight relationships between different elephant generations, in which ecological knowledge is transferred from matriarchs to younger individuals.

Nicole Garner Meeker
Writer

Nicole Garner Meeker is a writer and editor based in St. Louis. Her history, nature, and food stories have also appeared at Mental Floss and Better Report.