Tools are used by some animals, particularly primates, to perform simple tasks such as the acquisition of food, or grooming. Originally thought to be a skill only possessed by humans, tool use requires some level of intelligence. Primates have been observed exploiting sticks and stones to accomplish tasks. Numerous bird species have also been noted as capable of using tools. The behaviour has also been observed in dolphins, elephants, otters, birds and octopuses. Tools may be used by animals for construction.[1] Humans are the only animals known to build their own tools to accomplish a certain task, whereas animals appropriate found material like rocks or sticks.
Opposable thumbs are a benefit in tool use, though creatures without hands have managed to use other body parts to their advantage, notably the mouth.
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The key to identifying tool use is defining what constitutes a tool. Researchers of animal behavior have arrived at different formulations.
"An object that has been modified to fit a purpose" or "An inanimate object that one uses or modifies in some way to cause a change in the environment, thereby facilitating one's achievement of a target goal".—Hauser, 2000
"the use of physical objects other than the animal's own body or appendages as a means to extend the physical influence realized by the animal"—Jones and Kamil, 1973[2]
"an object carried or maintained for future use"—Finn, Tregenza, and Norman, 2009.[3]
Tool use implies that an animal has knowledge of the relationship between objects and their effects.
If an object is placed out of reach on a towel that itself is in reach, dogs, cats, and children will pull the towel to bring the object closer to them.
Sticks can be used to break into termite nests for food or even to fight rivals. They are sometimes used for grooming. Stones can be used, again, to fight rivals. However, they may also be used by more intelligent animals to carve bits of wood.
Some species such as the Woodpecker Finch of the Galapagos Islands use particular tools as an essential part of their foraging behavior. However, these behaviors are often quite inflexible and cannot be applied effectively in new situations. Several species have been shown to be capable of more flexible tool use. A well-known example is Jane Goodall's observation of chimpanzees "fishing" for termites in their natural environment, and captive great apes are often observed to use tools effectively. Several species of corvids have also been trained to use tools in controlled experiments, or use bread crumbs for bait-fishing.[4]
The animals that make the widest use of tools are humans, which have developed mechanical, electric and electronic tools for multiple purposes, far in advance of even the most advanced non-human animals.
Research in 2007 shows that chimpanzees in the Fongoli savanna sharpen sticks to use as spears when hunting, considered the first evidence of systematic use of weapons in a species other than humans.[5][6] Chimpanzees and bonobos were observed in the 1970s using sticks as probes to collect ants and termites. Dr. Jane Goodall, on Nov. 4, 1960, observed a chimpanzee using a grass stalk to extract termites. Also they have been observed cutting down the stick with their fingers and teeth so that it can fit into a hole in the ants' nest. They have even been observed using two tools, a stick to dig into the ant nest and a "brush" made from grass stems with their teeth to collect the ants.
In one troop of chimpanzees, it was observed that a female was using a stick to break into a bee hive to acquire honey. Both bonobos and chimpanzees have also been observed making "sponges" out of leaves and moss that suck up water and are used as grooming tools.
Gorillas have been observed using sticks to measure the depth of water and as "walking sticks" to support their posture when crossing deeper water.[7]
Orangutans have also been observed using sticks to measure the depth of water. It has also been observed that orangutans in Sumatra use sticks to acquire seeds from a certain fruit. This is because the lining of the inside of the fruit has hairs that sting. On the island of Kaja, a male orangutan was observed using a pole to acquire fish from a net after observing local humans spear fishing.[8]
Tool use has been observed in capuchin monkeys both in captivity and in their natural environments. In a captive environment, capuchins readily insert a stick into a tube containing viscous food that clings to the stick, which they then extract and lick.[9] Capuchins also use a stick to push food from the center of a tube retrieving the food when it reaches the far end,[10] and as a rake to sweep objects or food toward themselves.[11]
Wild capuchin monkeys in many areas use stone hammers and anvils to crack nuts and encased seed.[12][13] They transport stones and nuts to an anvil for this purpose.[14] Capuchins also use stones to excavate tubers and sticks to flush prey from inside rock crevices.[15]
Many birds have been shown to be capable of using tools. According to Jones and Kamil's definition, an Egyptian vulture dropping a bone on a rock would not be using a tool since the rock cannot be seen as an extension of the body. However, the use of a rock manipulated using the beak to crack an ostrich egg would qualify the Egyptian vulture as a tool user. Many other species, including parrots, corvids and a range of passerines, have been noted as tool users.[16]
New Caledonian Crows have been observed in the wild using stick tools with their beaks to extract insects from logs. While young birds in the wild normally learn this technique from elders, a laboratory crow named "Betty" improvised a hooked tool from a wire with no prior experience.[17] The Woodpecker Finch from the Galapagos Islands also uses simple stick tools to assist it in obtaining food. In captivity, a young Cactus Finch learned to imitate this behaviour by watching a Woodpecker Finch in an adjacent cage. Crows in urban Japan have innovated a technique to crack hard-shelled nuts by dropping them onto cross walks and letting them be run over and cracked by cars. They then retrieve the cracked nuts when the cars are stopped at the red light. In some towns in America, crows would drop walnuts onto busy streets and hope the cars would crack the nuts. Striated Herons (Butorides striatus) and Hooded Crows (Corvus cornix) use bait to catch fish.[18]
Seagulls have been known to drop live oyster shells on paved and hard surfaces so that cars can drive over them and break the shell. So many get dropped that it is hard to drive down pavements safely near waterways. Certain species (e.g. the Herring Gull) have exhibited tool use behavior, using pieces of bread as bait with which to catch goldfish, for example.[19]
Common ravens are one of only a few species who make their own toys. They have been observed breaking off twigs to play with socially.[20]
Many owners of household parrots have observed their pets using various tools to scratch the back of their necks, including bottle caps.
As of 2005[update], scientists have observed limited groups of Bottlenose dolphins around the Australian Pacific using a basic tool. When searching for food on the sea floor, many of these dolphins were seen tearing off pieces of sponge and wrapping them around their "bottle nose" to prevent abrasions.[21] Bottlenose dolphins have also been observed using conch shells to trap small fish, then lifting the shells out of the water causing the fish to fall into the dolphin's mouth.[22]
Dolphins are often seen engaging in playful behavior and create tools to use for entertainment. They have been observed blowing bubbles, which they form into rings to play with. After creating the bubble ring, a dolphin will use its nose and body to maintain the shape of the bubble and keep it from floating to the surface.
Sea otters have been observed using stones to hammer abalone shells off rocks. They hammer at a rate of 45 hits in 15 seconds or 180 rpm, and do it in two–three dives.[23]
Several species of wrasses have been observed using rocks as anvils to crack bivalve shells.[24]
As of 2009, the octopus is the only invertebrate animal which has been conclusively shown to use tools. At least four specimens of the Veined Octopus (Amphioctopus marginatus) have been witnessed retrieving discarded coconut shells, manipulating them, transporting them some distance, stacking them and then reassembling them to use as a shelter. This discovery was documented in the journal Current Biology and has been filmed on video. This can be seen as tool use because it uses the shells as an extension of its skin for protection against predators.
Elephants show an ability to use tools despite having no hands. Instead, they use their trunk much like one would an arm. Elephants have been observed digging holes to drink water and then ripping bark from a tree, chewing it into the shape of a ball, filling in the hole and covering it with sand to avoid evaporation. They would later go back to the spot for a drink. They also often use branches to swat flies or scratch themselves.[25] Elephants have also been known to drop large rocks onto an electric fence to either ruin the fence or cut off the electricity.[26] Elephants in captivity have been observed moving objects from one location to another in order to use them as stools to stand upon to access food that is otherwise out of reach.[27]
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