Tool use by animals is a subject of enormous controversy, for the simple reason that it's difficult to draw a line between hard-wired instinct and culturally transmitted learning. Do sea otters smash snails with rocks because they're intelligent and adaptive, or are these mammals born with this innate ability? Are elephants really using "tools" when they scratch their backs with tree branches, or are we mistaking this behavior for something else? On the following slides, you'll learn about 11 tool-using animals; you can decide for yourself just how smart they really are.
Coconut Octopuses
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Plenty of marine invertebrates hide opportunistically behind rocks and corals, but the coconut octopus, Amphioctopus marginatus, is the first identified species to gather materials for its shelter with apparent foresight. This two-inch-long Indonesian cephalopod has been observed retrieving discarded coconut half-shells, swimming with them up to 50 feet away, and then carefully arranging the shells on the seafloor for later use. Other octopus species also (arguably) engage in tool use, ringing their dens with shells, stones, and even bits of discarded plastic garbage, but it's unclear if this behavior is any more "intelligent" than, say, the nests built by terrestrial birds.
Chimpanzees
An entire article can be written about tool use by chimpanzees, but just one (grisly) example will suffice. In 2007, researchers in the African nation of Senegal documented over 20 instances in which chimpanzees used weapons while hunting, jabbing sharpened sticks into the hollows of trees to impale cowering bush babies. Weirdly enough, adolescent females were more likely than adolescent males, or adults of either sex, to engage in this behavior, and this hunting technique wasn't particularly successful, only one bush baby being successfully extracted.
Wrasses and Tuskfish
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Wrasses are a family of fish characterized by their small sizes, bright colors, and uniquely adaptive behaviors. One species of wrasse, the orange-dotted tuskfish (Choerodon anchorago), was recently observed uncovering a bivalve from the sea floor, carrying it in its mouth some distance away, and then smashing the unfortunate invertebrate against a rock--behavior that has since been replicated by the blackspot tuskfish, the yellowhead wrasse and the six-bar wrasse. (It doesn't really count as an example of tool use, but various species of "cleaner wrasses" are the car-wash attendants of the sea, gathering in groups to scour parasites off larger fish.)
Brown, Grizzly and Polar Bears
It sounds like an episode of We Bare Bears: a team of researchers from Washington State University dangled tasty doughnuts just out of the reach of captive grizzly bears, testing their ability to put two and two together and push over a nearby plastic box. Not only did most of the grizzlies pass the test, but brown bears have also been observed using barnacle-covered rocks to scratch their faces, and polar bears are known to hurl rocks or chunks of ice when acting out in captivity (though they don't seem to avail themselves of these tools when in the wild). Of course, anyone whose picnic basket has been swiped knows that bears are especially crafty scavengers, so this tool-using behavior may not be much of a surprise.
American Alligators
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Folks in the southeastern U.S. have long known that alligators and crocodiles are smarter than other reptiles, like snakes and turtles. Now, for the first time, naturalists have documented evidence of tool use by a reptile: the American alligator has been observed gathering sticks on its head during bird nesting season when there is fierce competition for nest-building materials. Desperate, unwary birds see the sticks "floating" on the water, dive down to retrieve them, and are turned into a tasty lunch. Lest you interpret this behavior as yet another example of American exceptionalism, the same M.O. has been employed by the appropriately named mugger crocodile of India.
Elephants
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Although elephants have been equipped by evolution with natural "tools," namely their long, flexible trunks, these mammals have been observed using primitive technology as well. Captive Asian elephants have been known to stomp on fallen branches, ripping off smaller side branches with their trunks, and then using these tools as primitive backscratchers. Even more impressively, some elephants have been seen covering up small watering holes with "plugs" made of stripped tree bark, which prevents the water from evaporating and also keeps it from being drunk by other animals; last but not least, some especially aggressive elephants have breached electric fences by battering them with large rocks.
Bottlenose Dolphins
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"Sponging" bottlenose dolphins don't borrow money from relatives; rather, they wear small sponges on the ends of their narrow beaks and burrow down into the seafloor in search of tasty grub, well-protected from painful injuries inflicted by sharp stones or offended crustaceans. Interestingly, sponging dolphins are primarily female; genetic analysis hints that this behavior originated generations ago in a single, unusually intelligent bottlenose and was passed down culturally through her descendants, rather than being hard-wired by genetics. Sponging has only been observed in Australian dolphins; a similar strategy, using empty conch shells rather than sponges, has been reported in other dolphin populations.
Orangutans
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In the wild, orangutans use branches, sticks, and leaves the way humans use utensils, screwdrivers and power drills. Sticks are the main all-purpose tool, wielded by these primates to pry tasty insects out of trees or dig seeds out of the neesia fruit; leaves are used as primitive "gloves" (when harvesting prickly plants), like umbrellas in driving rain, or, folded into tubes, as small megaphones that some orangutans use to amplify their calls. There are even reports of orangutans using sticks to measure the depth of water, which would imply a cognitive ability far in advance of any other animal.
Sea Otters
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Not all sea otters use stones to pulverize their prey but the ones that do are extremely nimble with their "tools." Sea otters have been seen wielding their stones (which they store in specialized sacs underneath their arms) as hammers to smash snails, or as "anvils" resting on their chests on which they dash their hard-shelled prey. Some sea otters even use stones to pry abalones off undersea rocks; this process can require two or three separate dives, and individual otters have been observed striking these unfortunate but tasty invertebrates as often as 45 times in the course of 15 seconds.
Woodpecker Finches
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One must be careful ascribing tool-using ability to birds, as these animals are hard-wired by instinct to build nests. Still, genetics alone doesn't quite explain the behavior of the woodpecker finch, which uses cactus spines to jostle tasty insects out of their crevices or even to impale and then eat larger invertebrates. Most tellingly, if the spine or twig isn't exactly the right shape, the woodpecker finch will fashion this tool to suit its purposes, which seems to involve learning by trial and error.
Dorymermex Bicolor
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If it can be difficult ascribing tool-using behavior to birds, it's an order of magnitude more difficult to attribute the same behavior to insects, the social behavior of which is hard-wired by instinct. Still, it seems unfair to leave Dorymermex bicolor off this list: these ants of the western U.S. has been observed dropping small stones down the holes of a competing ant genus, Myrmecocystus. No one knows where this evolutionary arms race is heading, but don't be surprised if millions of years down the line earth is inhabited by giant, armored, fire-spitting insects modeled after the alien arthropods in Starship Troopers.