Tool use by non-humans
Tool use by non-humans is a phenomenon in which a non-human animal uses any kind of tool in order to achieve a goal such as acquiring food and water, grooming, combat, defence, communication, recreation, or construction. Originally thought to be a skill possessed only by humans, some tool use requires a sophisticated level of cognition. There is considerable discussion about the definition of what constitutes a tool and therefore which behaviours can be considered true examples of tool use. A wide range of animals, including mammals, birds, fish, cephalopods, and insects, are considered to use tools.
Primates are well known for using tools for hunting or gathering food and water, cover for rain, and self-defence. Chimpanzees have often been the object of study in regard to their usage of tools, most famously by Jane Goodall, since these animals are frequently kept in captivity and are closely related to humans. Wild tool use in other primates, especially among apes and monkeys, is considered relatively common, though its full extent remains poorly documented, as many primates in the wild are mainly only observed distantly or briefly when in their natural environments and living without human influence. Some novel tool-use by primates may arise in a localised or isolated manner within certain unique primate cultures, being transmitted and practised among socially connected primates through cultural learning. Many famous researchers, such as Charles Darwin in his 1871 book The Descent of Man, have mentioned tool use in monkeys.
Among other mammals, both wild and captive elephants are known to create tools using their trunks and feet, mainly for swatting flies, scratching, plugging up waterholes that they have dug, and reaching food that is out of reach. In addition to primates and elephants, many other social mammals particularly have been observed engaging in tool use. A group of dolphins in Shark Bay uses sea sponges to protect their beaks while foraging. Sea otters will use rocks or other hard objects to dislodge food and break open shellfish. Several mammals of the order Carnivora have been observed using tools, often to trap prey or break open the shells of prey, as well as for scratching and problem-solving.
Corvids are well known for their large brains and tool use. New Caledonian crows are among the only animals that create their own tools. They mainly manufacture probes out of twigs and wood to catch or impale larvae. Tool use in some birds may be best exemplified in nest intricacy. Tailorbirds manufacture 'pouches' to make their nests in. Some birds, such as weaver birds, build complex nests utilising a diverse array of objects and materials, many of which are specifically chosen by certain birds for their unique qualities. Woodpecker finches insert twigs into trees in order to catch or impale larvae. Parrots may use tools to wedge nuts so that they can crack open the outer shell of nuts without launching away the inner contents. Some birds take advantage of human activity, such as carrion crows in Japan, which drop nuts in front of cars to crack them open.
Several species of fish use tools to hunt and crack open shellfish, extract food that is out of reach, or clear an area for nesting. Among cephalopods, octopuses are known to utilise tools relatively frequently, such as gathering coconut shells to create a shelter or using rocks to create barriers.
Definitions and terminology
The key to identifying tool use is defining what constitutes a tool. Researchers of animal behaviour have arrived at different formulations.In 1981, Beck published a widely used definition of tool use. This has been modified to:
Other, briefer definitions have been proposed:
Others, for example Lawick-Goodall, distinguish between "tool use" and "object use".
Different terms have been given to the tool according to whether the tool is altered by the animal. If the "tool" is not held or manipulated by the animal in any way, such as an immobile anvil, objects in a bowerbird's bower, or a bird using bread as bait to catch fish, it is sometimes referred to as a "proto-tool".
When an animal uses a tool that acts on another tool, this has been termed use of a "meta-tool". For example, New Caledonian crows will spontaneously use a short tool to obtain an otherwise inaccessible longer tool that then allows them to extract food from a hole. Similarly, bearded capuchin monkeys will use smaller stones to loosen bigger quartz pebbles embedded in conglomerate rock, which they subsequently use as tools.
Rarely, animals may use one tool followed by another, for example, bearded capuchins use stones and sticks, or two stones. This is called "associative", "secondary" or "sequential" tool use.
Some animals use other individuals in a way which could be interpreted as tool use, for example, ants crossing water over a bridge of other ants, or weaver ants using conspecifics to glue leaves together. These have been termed "social tools".
Borderline examples
Play
Play has been defined as "activity having no immediate benefits and structurally including repetitive or exaggerated actions that may be out of sequence or disordered". When play is discussed in relation to manipulating objects, it is often used in association with the word "tool". Some birds, notably crows, parrots and birds of prey, "play" with objects, many of them playing in flight with such items as stones, sticks and leaves, by letting them go and catching them again before they reach the ground. A few species repeatedly drop stones, apparently for the enjoyment of the sound effects. Many other species of animals, both avian and non-avian, play with objects in a similar manner.Fixed "devices"
The impaling of prey on thorns by many of the shrikes is well known. Several other birds may use spines or forked sticks to anchor a carcass while they flay it with the bill. It has been concluded that "This is an example of a fixed device which serves as an extension of the body, in this case, talons" and is thus a true form of tool use. On the other hand, the use of fixed skewers may not be true tool-use because the thorn is not manipulated by the bird. Leopards perform a similar behaviour by dragging carcasses up trees and caching them in the forks of branches.Use of bait
Several species of bird, including herons such as the striated heron, will place bread in water to attract fish. Whether this is tool use is disputed because the bread is not manipulated or held by the bird.Captive orcas have been observed baiting and catching a bird with a regurgitated fish, as well as showing similar behaviour in the wild.
Learning and cognition
Tool use by animals may indicate different levels of learning and cognition. For some animals, tool use is largely instinctive and inflexible. For example, the woodpecker finch of the Galápagos Islands use twigs or spines as an essential and regular part of its foraging behaviour, but these behaviours are often quite inflexible and are not applied effectively in different situations. The mechanisms driving other tool use, e.g. chimpanzee tool-use, are still debated. Whilst some may argue that behaviours such as using twigs to "fish" for termites, may be developed by watching others use tools and may even be a true example of animal teaching, studies with captive chimpanzees have found that many of these species-typical behaviours are individually learnt by each chimpanzee. Tools may even be used in solving puzzles in which the animal appears to experience a "Eureka moment".In mammals
Primates
Tool use has been reported many times in both wild and captive primates, particularly the great apes. The use of tools by primates is varied and includes hunting, collecting honey, processing food, collecting water, weapons and shelter.Tool manufacture is much rarer than simple tool use and probably represents higher cognitive functioning. Soon after her initial discovery of tool use, Goodall observed other chimpanzees picking up leafy twigs, stripping off the leaves and using the stems to fish for insects. This change of a leafy twig into a tool was a major discovery. Prior to this, scientists thought that only humans manufactured and used tools, and that this ability was what separated humans from other animals. In 1990, it was claimed the only primate to manufacture tools in the wild was the chimpanzee. However, since then, several primates have been reported as tool makers in the wild.
Both bonobos and chimpanzees have been observed making "sponges" out of leaves and moss that suck up water and using these for grooming. Sumatran orangutans will take a live branch, remove twigs and leaves and sometimes the bark, before fraying or flattening the tip for use on ants or bees. In the wild, mandrills have been observed to clean their ears with modified tools. Scientists filmed a large male mandrill at Chester Zoo stripping down a twig, apparently to make it narrower, and then using the modified stick to scrape dirt from underneath his toenails. Captive gorillas have made a variety of tools.