The 13 Least Intelligent Animals in the World (2025 Edition)

People often marvel at how much—and how little—intelligence is displayed in the animal kingdom. Often the subject of research, animal intelligence is just plain tough to nail down. Mammals and birds are often regarded as having superior intelligence compared to reptiles, fish, and insects, but several of them behave and live in ways that just make us scratch our heads.

The animals on this list shine for all the wrong reasons. Nevertheless, their odd behaviors and lives are working for them; after all, they aren’t extinct (no matter how hard they may be trying to be). Just remember the words of one of the most brilliant human beings, Albert Einstein: “If you judge a fish by its ability to climb a tree, it will live its whole life believing that it is stupid.”

Let’s take this list of the world’s least intelligent animals (in no particular order) with a grain of salt and loads of laughter.

#1 Horned Lizard

Fat, lazy, toxic, and not worth the effort are how natural predators of the horned lizard might describe this reptile. Horned lizards appear to make very little effort to eat. They wait for unsuspecting prey to walk by, then snatch them up. They spend the rest of their time doing little else, hence their reputation for being lazy. Predators learn that horned lizards can inflate their bodies to twice their size to ward them off, and a special duct near their eyes shoots foul-tasting blood up to three feet away. The substance is toxic to canines (dogs, wolves, and coyotes). This creature’s uneventful daily life is what has earned its spot on this list. It just doesn’t seem to do anything useful.

#2 Cane Toads

Lack of discernment lies at the foundation of this rather primitive-behaving amphibian. Native to South and Central America and an invasive pest in Australia, cane toads will eat both living and dead matter and will attempt to breed with any creature that they can “tame,” even rats, lizards, and snakes, a task that isn’t terribly difficult. Cane toads’ skin and the parotoid glands behind their eyes secrete a toxic and hallucinogenic milky-white fluid known as bufotoxin when threatened. Their diet is actually the less strange behavior. If their reproductive zeal is rooted in propagating their species, it continues to confound scientists, as female cane toads can lay nearly 30,000 eggs in a single clutch several times a year—and they do!

#3 Bees

Bees live a remarkably structured existence most of the time. In the summer months, as temperatures and humidity rise, nectar, tree sap, and even rotting fruit can ferment to create ethanol. The bees that ingest too much of these fermented fluids will begin displaying behavior that resembles drunkenness. Like people, these intoxicated bees will show signs of impaired judgment: confusion about their whereabouts, difficulty flying, and slowed reactions to stimuli. When intoxicated bees return to the hive, guard bees will refuse entrance to these bees to the hive as fermented nectar could risk the entire hive and its operation. These refusals can turn violent, often with the disoriented bees losing their wings and legs. It seems even the natural word requires Alcoholics Bee-Anonymous.

#4 Killdeer Bird

The killdeer’s shrill two-syllable chirp is the Marvel comic equivalent of Captain America’s famous catchphrase: “I can do this all day.” Killdeers, particularly the males, cannot seem to take a moment of silence as they are seen and heard—day and night—screeching “kill-deer,” “kill-deer,” “kill-deer.” These birds also build their nests on the ground. Predators surely see these birds and their young as easy marks. The behavior of these birds upon a predator’s arrival near a nest further baffles the mind. Killdeers will taunt the predator.

Once they spot a predator, killdeers will leave their nest to approach the predator, at which point they will attempt to distract the predator by either running toward it screaming the notable call or using the “broken-wing display.” Both behaviors are mostly deployed during breeding season when their young are incubating, and the intensity of their display grows as the eggs get closer to hatching. These birds will finally flee just before the predator strikes, flying off to return to its nest.

#5 Secretary Bird

Looks can be deceiving. Don’t judge a book by its cover. Unfortunately for secretary birds, they look ridiculous and therefore have earned a reputation for being a bit dumb, regardless of the evidence. These birds resemble a creation from the imagination of an 8-year-old. They couldn’t possibly be real, or real and smart. Their head and body recall those of an eagle; their legs could belong to a stork, crane, or other thin, long-legged avian species. Secretary birds can stand as tall as, or taller than, 4 feet.

Despite their unusual appearance, these birds of prey are excellent hunters and utilize their lengthy legs and sharp talons to hunt prey and defend themselves. Secretary birds weigh, on average, about 7 pounds, but they can stomp with a force equal to 36.5 pounds and deliver a fatal blow in just 15 milliseconds.

#6 Northern Fulmar

It’s quite a wonder that northern fulmars, gull-like seabirds, enjoy “Least Concern” status on the IUCN Red List. Females lay one—yes, one—egg in a clutch. Their nests sit high on rocky or grassy cliffs along the coldest coasts in the world, the North Atlantic, North Pacific, and Arctic oceans. At hatching, their offspring is downy, completely dependent, and unable to fly in some of the harshest conditions on earth; their eyes are open, though, so not entirely helpless. These birds only return to land to lay that single egg and feed it.

These birds hold an ace under their wings. The northern fulmar’s proventriculus, a standard part of avian anatomy, does double duty. The proventriculus stores a stomach oil composed of wax esters and triglycerides that provide an essential source of sustenance during their long flights at sea, and this mixture serves as a potent deterrent to predators such as other birds and foxes. How? They can projectile vomit this substance onto them. Both adult and young fulmars can do this. This oil drenches the wings of predatory birds, spelling death for them as they will be unable to remove the oily blend and therefore fly. For land predators, the rancid odor left by the oil alerts potential future prey to their presence, giving potential meals an opportunity to escape the hungry clutches of starving hunters.

#7 Kakapo

Flightlessness seems to be the feature of note for many New Zealand birds. The kiwi bird is the country’s most famous emblem. There is, however, another flightless bird native to New Zealand; this one does not enjoy the regard and accolades of its very distant cousin. Articles abound online about how kakapos (Strigops habroptilus) are the ugly, red-headed stepchild of the avian world. The reason for the harsh verdict? They appear to have little to no regard for their own lives as they will freeze in the presence of mammalian predators. They simply don’t put up a fight. There is a perfectly good reason for this.

At one time, long ago, the nocturnal kakapo’s only predators were birds of prey. These birds typically hunt during the day, using their excellent vision to find their meals, when kakapos are the least active. During the day, their plumage allows them to easily blend into the vegetation. Things changed for kakapos with the introduction of a number of mammals, including dogs and cats, to New Zealand. Mammals often hunt at night and use their senses of smell and hearing to locate prey. Kakapos’ incredible ability to camouflage is just not an effective strategy to avoid this new category of predator. In other words, these birds were never meant to deal with mammalian predators. But, then again, these birds have had some time to learn a few things, and they haven’t.

#8 Norway Lemmings

No, Norway lemmings do not commit mass suicide, but they do display another behavior en masse. When the need arises, for example, their population becomes too large or resources become scarce, these lemmings will mass migrate in search of a more plentiful place to live; if their migration requires a water crossing, they’ll go through rather than around, and several often perish. These animals are very communal, so it would seem that they would learn or be able to ration resources better. Furthermore, though these animals “be but little, [they are] fierce.” Norway lemmings grow on average to be 6 inches long and weigh 4.5 pounds, but they regularly display aggression toward larger animals such as cats, dogs, and birds of prey. This does not appear to be a wise tactic, although they do have very strong teeth, which they use as a defensive weapon. This, of course, requires that these lemmings permit their predators to come close to them. It is believed that their distinctive white cheeks and chin draw their predators’ attention toward their mouths.

#9 Slow Loris

Cute doesn’t always translate to brains. Slow lorises are small, nocturnal primates with giant eyes and chubby faces that live in Southeast Asia. The adjective in their name refers to the slow, deliberate, and nearly silent movements they make, especially when threatened. Slow lorises do not flee those that would make them a meal. Instead, they remain motionless, and they can stay immobile for lengthy periods of time. It seems far more reasonable to flee, but this may not the brightest primate in the jungle (at least by human standards)—or is it?

These primates have a toxic bite, which is quite rare among mammals and downright special to this species of primate. In order to ward off predators, this would require slow lorises to allow them to get quite close—a strange and uncommon behavior for a prey animal. A secretion is produced in the brachial (or sweat) gland on their arms and becomes activated when it mixes with their saliva. And there is some evidence to suggest that their toxic bite is used to settle disputes between fellow lorises rather than to fend off predators.

#10 Koala

Good looks only get you so far, so they say. The koala has a reputation for being the cutest, cuddliest non-bear and for being one of the dumbest and laziest animals alive. The Australian marsupial spends its days, according to urban legend, getting high on eucalyptus leaves, which contain a number of toxins. While these toxins create a hurdle for other animals, they do not for koalas. Conserving energy is the name of the koala game. These animals have a very slow metabolic rate, which means they need a lot of time to digest their food and extract the necessary nutrients/energy from it. Their digestive system is up to the task. Like other mammals, koalas have a caecum (cecum), but theirs is nearly six feet long, and it aids in digesting the fibrous eucalyptus leaves. The perceived laziness of the koala is a strategy for conserving energy when they need it most: to flee a predator, for example. In other words, the koala’s best virtue is patience.

#11 Sloth

Sloths hit the big time after the Ice Age movies, thanks to the popularity of one of the main protagonists, Sid the Sloth. Portrayed as simple-minded and lazy (he always wanted Manny the Mammoth to carry him), Sid the Sloth somehow always managed to come out on top—and this was primarily attributed to dumb luck. This is keeping in line with the world’s impression that the slow-moving sloth is just not the sharpest tool in the shed. While sloths may not be winning any intelligence competitions with other tree-dwellers (i.e., primates), they are perfectly designed for the ecosystem in which they live.

The Central and South American tree dwellers have the lowest metabolic rates of any non-hibernating mammals, but they move three times faster in water than they do on land, float, and are incredibly strong, despite having 30% less muscle mass than other animals of a similar size. They don’t move quickly because their predators such as the harpy eagle can detect the most minute movements. Slow may suggest stupid, but that doesn’t really seem to be the case here, does it?

#12 Giraffes

The distance from hoof to nape on giraffes is greater than the length of their neck. In other words, giraffes cannot grab a quick, cool drink from a desert oasis without having to splay their front legs apart. Additionally, as the tallest mammal in the world, with a neck as long as 6 feet, it is assumed that this feature aligns perfectly with their habitat, meaning giraffes use their extreme height to reach the leaves of towering trees. This assumption would be incorrect: The savannas of East Africa, where they live, does not have very tall trees.

Long believed by humans to be one of nature’s dumbest creations, giraffes have proved to be a bit smarter than first believed. These animals communicate using moans and grunts at a frequency that we cannot readily hear. They also communicate with each other by using their eyes and touching each other. Also, their height isn’t entirely strange or useless. Their long legs provide them with an effective defense against pesky predators. Giraffes can kick, quite lethally, too, in every direction with accuracy. And if their legs get tired, giraffes will swing their necks like a billy club to ward off attacks.

#13 Panda

Like the other animals on this list, giant pandas suffer from a PR problem, often overlooked because they are considered one of the cutest, cuddliest creatures in the world. Pandas are simply regarded as brainless beauties for a number of reasons: They seem clumsy, lazy, and uncoordinated; they spend hours and hours eating bamboo, only to eat more; they are a bear that doesn’t hibernate; and they don’t seem to have an interest in sex and therefore the propagation of their species. Is it any wonder why this species is fighting extinction? They just do weird things—or do they?

It is posited that the reason for pandas’ clumsy behavior is that sometimes the easiest, fastest, lowest-energy way to get somewhere is to fall or roll there. Their rounded frames and short limbs may be just perfect for tumbling. They also seem to like it. Their unconventional mode of movement may also be linked to their diets. While technically carnivores, pandas eat a mostly herbivore diet. They can only digest about 17% of the 26-84 pounds of bamboo they eat daily, so they aren’t getting a lot of nutrients/energy from their meals. Nevertheless, they have an enlarged radial sesamoid bone, or “false-thumb,” that allows them to hold bamboo sticks in their palms (paws) and a complex suite of gut microbes to help with digestion. Much of what we know about pandas comes from studying them in captivity. Like people, pandas may find it difficult to show an interest in sex when under the watchful eye of research scientists.

A symbol for peace in China, pandas seem to do well in the wild—capable of defending themselves from predators, of finding mates and procreating, and happily tumbling about in their natural habitat without judgment. It seems pandas only seem stupid to us.