The use of tools is an extraordinarily diversified and widespread phenomenon among insects, birds, and mammals. ~ Edward O. Wilson
Employing tools, especially their manufacture to intended uses, demonstrates goal orientation and tactical thinking. The same applies to other strategies that confer gain, irrespective of tool use.
Tools garner a more favorable impression than subtle subterfuges simply because they are artifacts of manipulation. Hard evidence is reassuring to the empirically minded.
Tool use is intelligent when learned patterns of tool use are predicated on the formation and manipulation of internal representations. Many other behaviors, not involving tools, are also predicated on internal representations and are also intelligent. ~ American zoologist Benjamin Beck
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Almost everywhere they live microbes jostle for space and compete for resources. Some bacteria evolved a speargun that they can use to inject a toxic cocktail into rivals, thus eliminating them. The weapon is a sheath containing a sharp-tipped spear. The sheath comprises over 200 connected, cogwheel-like protein rings assembled around the inner rigid spear. When a bacterium fires, the sheath rapidly contracts and pushes the toxic spear out of the cell, which then penetrates a neighboring cell, where it releases deadly toxins.
Pavement ants are fond of honey. If they find a bee’s nest, they’ll drop dirt on the guard bees at the entrance to a hive, knocking them silly or dead; so the raid begins.
Florida harvester ants make pellets by combining sand grains which they dip into honey. The pellets absorb the honey and are then carried back to the nest.
Dolichoderine ants bombard the entrance of the nests of their competitors. A troop will stone emerging ants as they leave the entrance to prevent them from foraging.
As an aid to capture, antlions flick sand grains at prey that fall into their pits.
A female sand wasp builds a nest for her eggs in sandy ground. She digs a vertical shaft in which she will lay her egg. Then the wasp provisions the burrow with a caterpillar she has paralyzed. As a finishing touch, the sand wasp plugs the nest, else the food supply might attract hungry mouths. She covers the hole with sand, but there is the danger of disturbance if the sand is too loose, so the wasp searches for a pebble not quite as large as her head. Holding the stone in her mandibles, she tamps down the sand until it is well-packed; whereupon her maternal task is accomplished.
Other wasp species – in the Ammophila and Sphex genera – pick up a suitable object in their jaws, whether pebble or wood chip, and use it to tamp down a bit of soil to seal and conceal a laid egg.
Funnel ants use bits of leaf or wood to soak up semi-liquid foods, such as fruit pulp, or the body fluids of prey. Funnel ants then carry the sponge back to the colony nest. This lets them transport up to 10 times as much liquid as they could carry otherwise.
Funnel ants tend aphids that live on plant roots, providing much of their sustenance. Subsisting in a subterranean lifestyle, these ants rarely appear on the surface.
Funnel ants were named from their practice of building funnel-shaped openings to their underground abodes. Hapless arthropods drop in for dinner, with themselves as the main course. The antlion pit ploy independently evolved in ants.
There are some 4,000 species of assassin bugs, which characteristically use subterfuge to lure their prey, whereupon they literally suck the life out of them.
One assassin bug lives up to its name with its termite fishing techniques. To disguise its own scent with termite pheromones, an assassin bug picks up bits from near a termite nest and rubs them over its body.
This lets the bug approach a nest opening without setting off a general termite alarm. Having caught a termite and sucked out its tasty innards, an assassin bug will dangle the corpse at the nest opening, baiting other termites to investigate, and thereby become the bugs’ next morsel. One assassin bug with a hearty appetite was seen serially consuming 31 termites with these tricks.
A masked hunter, a type of assassin bug, takes on the guise of a walking dust bunny by picking up and covering itself with various debris, from dust to dead bugs. Bed bugs and flies take the curious bait for a short-lived date.
Assassin bugs that are bee killers collect plant resin on their front legs; then, patiently poised on flowers, use the sticky stuff to grab and hold bees.
Certain assassin bugs in Asia and Australia lure ants with a special sugar-producing structure on their abdomens. The predator places itself on an ant pathway and waits. A victim, drawn to the sweet scent, consumes a bit of the assassin bug’s secretion, which is laced with a tranquilizer that immobilizes the ant. Dinner is served.
Another assassin bug, the Australian thread-legged bug, looks like a small walking stick. It is light enough to walk on a spider web undetected. The thread-legged bug is wily enough to steal spider-captured food from a web when the resident spider is not paying attention. It may even play the silk threads of a spider web like an insect struggling to escape, then attack the resident spider and suck it dry.
Sea urchins drape themselves with shell fragments, algae, pebbles, or other debris for camouflage.
Boxer and hermit crabs use stinging anemones as a shield: prying or picking them up and holding them to ward off attackers or placing them so that an anemone might attach itself onto the crab’s shell to act as a protective device. The crabs are careful in detaching the small anemones from their original substrate, as they are useless as tools if injured.
Hydrozoa are a diverse group of tiny marine animals. Some are solitary, others genetically gregarious. The Portuguese man o’ war is a colonial hydrozoan.
While certain hydrozoa are inveterate drifters, some live sedentary lives: the misnamed fire coral deposits a calcareous skeleton and settles in a coral reef, ignoring its taxonomic differences to true corals by blending in.
Countless species of hydrozoa latch onto something to make a living, whether seagrass blades, animal shells, or just bare rock. Conversely, some hydrozoa are latched onto, and used to fish.
Decorator crabs earned their title by stylishly employing materials to hide from or ward off predators. Some decorators do more than that with selective clientele.
Decorating spider crabs prize a certain hydrozoan which has sticky polyps that can readily capture planktonic prey. The crabs purposely place these hydrozoa on the legs they wave in the current to catch their meals. The hydrozoa are better placed for foraging than they might otherwise be, but they lose a goodly share of the profits to their investors.
Tool use varies greatly among vertebrates. For some, it is as simple as spitting water, which is not actually simple at all.
Archerfish are terrific spitters. On the prowl near the water’s surface, they prey on insects and other small fare on land – grasshoppers, butterflies, spiders – by accurately shooting a tight spout of water from their mouths, stunning the target with their spit.
With luck, the meal-to-be plops into the water for convenient pickup. Otherwise, if the prey is within jumping reach, an archerfish will leap out of the water and grab lunch.
It takes a powerful punch to knock an insect off its leaf. An insect in repose is usually firmly anchored, with a force 10 times its body weight. Yet, in a fraction of a second, an archerfish pops one off its perch.
The impact of an archerfish spit is 3,000 Watts/kilogram; well above the maximum vertebrate muscle power of 500 W/kg.
Amplification of muscle power occurs outside the archerfish: by creating a hydrodynamic instability in its spit stream, akin to that used for inkjet printing. The archerfish modulates the velocity of the jet coming out its mouth to achieve a gradual increase of mass and velocity accumulated at the head of the jet. The technique forms a single, large, water drop that abruptly smacks the prey with a powerful punch.
Archerfish load up according to the size of the prey: using more water for larger, heavier targets. An archerfish may squirt a single shot or spray a fusillade.
An archerfish must accurately gauge its prey’s distance for the jet to coalesce into maximum impact. Knowledgeable archers may aim just below their prey, to knock it straight down into the water instead of whisking it away in a straight-on shot.
Experienced spitters have close to a 100% hit rate. By stark contrast, young archerfish don’t have the knack.
Spitting skill is not innate. Accuracy takes practice. Fry hunt in small schools, improving the odds of shooting a meal; though inexperienced individuals cannot successfully hit a target if it is moving even a centimeter a second.
Target-shooting lessons can come at someone else’s expense. Archerfish live in groups and have fantastic observational learning ability.
Inexperienced archerfish extensively watch others to learn technique. After watching 1,000 attempts, regardless of success, novices have learned enough to make successful shots at rapidly moving targets.
Observational learning ability is termed perspective-taking. An archerfish can mentally assume the viewpoint of the fish it is watching to fully appreciate the experience.
Archerfish pick out their stationary targets using the same mental search strategies that humans employ in trying to discern objects in a cluttered background. For moving targets, they adjust the trajectory of their jets based upon the speed that the target is moving: aiming farther ahead if the prey is flying faster.
Archerfish compensate for the optical distortion produced by the water-to-air transition. This requires learning the physics involved with distance, relative position, and target size.
If a target is flying low, archerfish use the sophisticated stratagem of turn-and-shoot. The fish fires while simultaneously rotating its body horizontally to match the lateral movement of the target. Thus, the ejected jet of water tracks the target on its airborne path.
Archerfish are adept entomologists: visually identifying insects to know whether they are tasty (and stingless), and nutritious enough to go to the bother. If dinner is not in the air, archerfish readily forage like any other fish lacking the skill to spit.
Archerfish also use their spitting ability underwater to stun prey hiding in sediment. The fish alter the blast to suit the type of sediment.
Archerfish use the same dynamic mechanism to produce aerial and underwater jets. They employ the same basic technique to adjust their jets in both conditions. ~ German animal physiologist Jana Dewenter et al
How archerfish are able assess sediment characteristics before taking a shot is not known. Doubtlessly it is an acquired skill.
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Archerfish are not the only fish interested in tasty tidbits that fall in. Halfbeaks will happily steal the fruits of archerfish labors.
This rivalry prompted adaptations. Archerfish evolved to predict the trajectory of a falling prey, launching themselves where it will it hit the water while still coming down. This allows archerfish to beat halfbeaks by an average of 163 milliseconds: a close race. That is during the day. At night, halfbeaks have the advantage. Archerfish rely upon their vision to get a jump start.
Halfbeaks have 5 times as many sensory cells on their backs as archerfish. This gives halfbeaks greater accuracy in detecting the waves of prey which have hit the drink.
Archerfish win when they can use vision, but halfbeaks win in the dark. ~ German marine biologist Stefan Schuster
An orange-dotted tuskfish off Palau digs a clam out of the sand, carries it to a rock, and repeatedly slams the clam against the rock until the shell is crushed enough for the fish to get at the clam. Tuskfish are in the wrasse family, one of the largest and most diverse families of marine fishes.
Wrasses are typically inquisitive. All are carnivorous, with sharp eyes and a sensitive sense of smell. Various wrasse have been observed using tools.
Some fish – including the South American cichlid and the brown hoplo – lay their eggs on leaves, which they move to a more protected area if the present home ground appears threatened.
Amphibians and reptiles are not big tool users. Horned frogs bury themselves in the ground as a hunting technique. If they aren’t completely covered, they’ll pitch lumps of dirt on their backs using their feet.
Crocodiles lure birds using fish bait. After eating much of a fish, chunks will be left floating on the water’s surface. A crocodile will submerge itself underwater, with only its eyes sticking out, awaiting a scavenger to fly down and help itself to the scraps. Similarly, to lure avian nest builders, crocodiles put suitable sticks on their snouts.
Herons, gulls, and kingfishers break food up to serve as fishing bait. Great herons drop leaves or small sticks into moving streams and then run downstream to snatch any small fish that their lure has attracted. Burrowing owls place dung out as bait for dung beetles, then wait motionless for their arrival.
An African black egret uses its body as a tool: forming a tent-like canopy with its wings to create a shaded area from the blazing African Sun, drawing unsuspecting fish looking for a place to shelter. Black egrets do not make wing tents in the early morning or when it is cloudy. Instead, they merely stroll along to find fish.
Egyptian vultures drop stones on ostrich eggs to break the tough shell. On the wing Australian black-breasted buzzards drop rocks on emu eggs to crack them.
There have been many reports of other birds dropping objects to desired effect, including a male osprey bombing an intruder osprey with rocks, and a sulfur-crested cockatoo dropping twigs onto a pair of bat hawks sitting on a lower branch of a tree.
A song thrush at its anvil – hammering a snail-shell against a rock – is a familiar sight in European gardens. The thrush knows just how to crack away to loosen a snail’s grip on its shell. Naked snails are slimy, so a thrush wipes the snail off on the ground, to remove as much mucus as possible, before swallowing it.
Black kites are called fire hawks by indigenous Australians. The kites pick up smoldering sticks from a brush fire, drop the twigs on unburned grass, then swoop to feed on the small animals fleeing the fresh fire.
Bald eagles are known to thrown stones, as are black-breasted buzzards. Bristle-thighed curlews have been seen flinging coral pieces to break eggs.
White-winged choughs drop or throw previously consumed mussel shells to break fresh mussels. Choughs also use shells to pound on the next mussel meal.
Wild Australian brush turkeys accurately kick dirt and debris to thwart attack – such as against a lace monitor lizard.
Woodpecker finches use twigs or cactus spines to pry insects out of crevices and cavities in trees, as do pygmy nuthatches and mountain chickadees. Using these picks lets them reach otherwise inaccessible prey, largely hidden from view.
Woodpecker finches, endemic throughout the Galápagos Islands, have no choice but to resort to tools: their tongue is too short to be of much use. At least half of this finch’s food is had through tool use, making woodpecker finches the most proficient tool users besides humans.
Woodpecker finches forage using different stratagems, depending upon the season and habitat. Insects in cracks and crevices are impaled or preyed out with a sharp stick or cactus spine.
Wood-boring grubs must first be accessed. A woodpecker finch begins by pecking a hole in the branch until it reaches the grubs’ den. The finch then flies off to select a suitable tool for excavation. Probing the tool deep into the hole either drives the prey out or is used as a lever to prize a grub to the surface.
Failing to find the perfect implement is no impediment to a woodpecker finch. If no suitable twig or spine is readily available, a bird selects a larger item and whittles it down to size, removing any side-projections in the process.
An African grey flycatcher was seen fishing for a winged termite with a grass blade by sticking it into a hole. The flycatcher pulled the blade out when a termite had grabbed it with its mandible.
Hyacinth macaws use wood slivers or leaves to wedge nuts open. Caged yellow-crowned parakeets use twigs to rake in seed that could not otherwise be reached.
Great herons drop one of their own feathers on to the water as fish bait. Unsuspecting prey respond to this novel object by closer inspection, nibbling to check for food potential; whereupon the heron stabs the fish and eats it.
A white stork mother gives her chicks a drink by squeezing damp moss with her beak. A male gila woodpecker dips a bit of bark into honey to soak it up, then takes the honeyed bark back to waiting nestlings. Brewer’s blackbirds soak grasshoppers in water to soften them up before taking them back to their fledglings at the nest. Over 30 species of birds have been observed dipping or soaking their food in water before swallowing it.
Dozens of different birds have been seen using tools. Finches, parrots, and corvids are notable for making tools, typically by pulling suitable twigs from trees. Individuals in practically all of the 120 species of corvids may cagily fashion and use a tool if the need arises and materials are available.
They are in a special situation with unpredictable resources. ~ Austrian ornithologist Alice Auesperg
The Tanimbar corella is a small white cockatoo endemic to the islands of the Tanimbar archipelago in Indonesia. Like most corellas, they live in social groups of 10–100, roost in tree holes, and mostly eat seeds and nuts.
The Tanimbar corella can solve problems involving sequential steps. This corella is also able to solve complex mechanical problems.
Besides learning from others, and by trial and error, corellas spontaneously innovate to make tools to accomplish desired tasks. They are quick to adapt their behavior when a situation changes.
Male Tanimbar corellas are better problem solvers than females. They need to be, as they must supply females with what they need at the nest.
Both sexes exhibit self-control for anticipated gain. An experiment showed that they would resist eating one nut (a pecan) given to them to trade up to a more desirable nut (a cashew).
The Tanimbar corella is a demanding pet. Being as smart as it is, this bird easily gets bored.
He must have been trained for this. As soon as the police got close, he started shouting. ~ Brazilian policeman
Brazilian vice cops took into custody a parrot who had alerted its owner of a drug raid by shouting: “Mum, the police!” Once arrested, the parrot refused to speak – determined not to be a stool pigeon.
For all its apparent cleverness, tool manufacture and use are not necessarily a sign of a smarter bird. Tool-using woodpecker finches are no more adept at tasks than other individuals in the same population that don’t bother with tools. The closely related small tree finch, which never picks up a tool, does just as well.
So, a tool is just a tool, and an unreliable indication of comparative intelligence. Tool use in captive birds and mammals is more prevalent than in wild counterparts because prison can drive anyone stir crazy.
With exceptions, mammals are not big tool users; no more than certain insects, such as ants. The most prominent exceptions are marine mammals, rodents, elephants, and some primates who often avidly use tools.
For primates, tool use is opportunistic. Upon finding a food resource better accessed using a tool, if the materials to make a tool are available, a monkey or ape can rather ingeniously figure out how to construct and use a tool to get at the food. If tool materials are not available, so it goes; but not always. A chimp may travel a kilometer to obtain the right material to use as a tool. Tasty treats are worth the trouble.
Numerous carnivores enlist the use of hard objects to help them break into protected food. Monkeys often crack open crabs and nuts with stones: either bashing the food against a rock, or vice versa. Sea otters do the same with the bivalves they eat.
Ever-nutritious eggs are especially prized. The trick is getting them open. Skunks and mongooses have special body movements that let them fling bird eggs against rocks with aplomb. Lions, though attracted to ostrich eggs, have no special method of opening them, and therefore often find such eggs a source of frustration rather than sustenance.
Even in mammal species inclined to tools, use is often cultural: limited to certain individuals or groups. In contrast, insects that use tools consistently do so.
Wolverines live in cold mountainous forests. They are opportunistic foragers that survive the harsh winters by caching food in preparation for the lean months. To prevent microbial and insect scavengers from eating their caches, wolverines smartly tuck their supplies into crevices that provide refrigeration. Caching cool is a tool.