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 (mammals, invertebrates, fish), collecting honey, processing food (nuts, fruits, vegetables and seeds), 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, the primatologist Jane 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.
Taxonomic range
Chimpanzees and bonobos
Chimpanzees are sophisticated tool users with behaviours including cracking nuts with stone tools and fishing for ants or termites with sticks. These chimpanzees not only use these sticks to fish out their meal, but they in fact build their own 'tool kits' to do so, as observed in the Republic of Congo. They first use a smaller stick to break open the termite or ant mound, then use a large stick to make holes in the prey's colony, and then insert a 'fishing probe' into the hole and pull out all the termites or ants that have gathered on the stick. Chimpanzees were found to deliberately choose plants that provide more flexible tools for termite fishing. There are more limited reports of the closely related bonobo (Pan paniscus) using tools in the wild; it has been claimed they rarely use tools in the wild although they use tools as readily as chimpanzees when in captivity, It has been reported that females of both chimpanzees and bonobos use tools more avidly than males. reported a case when two female chimpanzees had the keys to their cage accidentally left at least away from it, and managed to use objects at hand as improvised tools to retrieve them and get out.Complex Tool Activity according to L. A. Firsov's observations. Wild chimpanzees predominantly use tools in the context of food acquisition, while wild bonobos appear to use tools mainly for personal care (cleaning, protection from rain) and social purposes. Wild bonobos have been observed using leaves as cover for rain, or the use of branches in social displays.
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 (UK) 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.
Hunting
Chimpanzees sharpen sticks to use as weapons when hunting mammals. This is considered the first evidence of systematic use of weapons in a species other than humans. Researchers documented 22 occasions when wild chimpanzees on a savanna in Senegal fashioned sticks into "spears" to hunt lesser bushbabies (Galago senegalensis). In each case, a chimpanzee modified a branch by breaking off one or two ends and, frequently using its teeth, sharpened the stick. The tools, on average, were about long and in circumference. The chimpanzee then jabbed the spear into hollows in tree trunks where bushbabies sleep. There was a single case in which a chimpanzee successfully extracted a bushbaby with the tool. It has been suggested that the word "spear" is an overstatement that makes the chimpanzees seem too much like early humans, and that the term "bludgeon" is more accurate, since the point of the tool may not be particularly sharp. This behaviour was seen more frequently in females, particularly adolescent females, and young chimps in general, than in adult males.
Chimpanzees often eat the marrow of long bones of colobus monkeys with the help of small sticks, after opening the ends of the bones with their teeth. A juvenile female was observed to eat small parts of the brain of an intact skull that she could not break open by inserting a small stick through the foramen magnum. On another occasion, an adult female used three sticks to clean the orbits of a colobus monkey skull after she had just eaten the eyes.
In Gombe National Park in 1960, Jane Goodall observed a chimpanzee, David Greybeard, poking pieces of grass into a termite mound and then raising the grass to his mouth. After he left, Goodall approached the mound and repeated the behaviour because she was unsure what David was doing. She found that the termites bit onto the grass with their jaws. David had been using the grass as a tool to "fish" or "dip" for termites. Soon after this initial discovery of tool use, Goodall observed David and other chimpanzees picking up leafy twigs, stripping off the leaves, and using the stems to fish for insects. This modification of a leafy twig into a tool was a major discovery: previously, scientists thought that only humans made and used tools, and that this was what separated humans from other animals.
Other studies of the Gombe chimps show that young females and males learn to fish for termites differently. Female chimps learn to fish for termites earlier and better than the young males. Females also spend more time fishing while at the mounds with their mothers—males spend more time playing. When they are adults, females need more termite protein because with young to care for, they cannot hunt the way males can.
Populations differ in the prevalence of tool use for fishing for invertebrates. Chimpanzees in the Tai National Park only sometimes use tools, whereas Gombe chimpanzees rely almost exclusively on tools for their intake of driver ants. This may be due to difference in the rewards gained by tool use: Gombe chimpanzees collect 760 ants/min compared to 180 ants/min for the Tai chimpanzees.
Some chimpanzees use tools to hunt large bees (Xylocopa sp.) which make nests in dead branches on the ground or in trees. To get to the grubs and the honey, the chimpanzee first tests for the presence of adults by probing the nest entrance with a stick. If present, adult bees block the entrance with their abdomens, ready to sting. The chimpanzee then disables them with the stick to make them fall out and eats them rapidly. Afterwards, the chimpanzee opens the branch with its teeth to obtain the grubs and the honey.
Chimpanzees have been observed using a pair of tools to accomplish a task: a stick to dig into an ant nest and a "brush" made from grass stems with their teeth to collect the ants.
Collecting honey
Chimpanzees eat honey of four bee species. Groups of chimpanzees fish with sticks for the honey after having tried to remove what they can with their hands. They usually extract with their hands honeycombs from undisturbed hives of honey bees and run away from the bees to quietly eat their catch. In contrast, hives that have already been disturbed, either through the falling of the tree or because of the intervention of other predators, are cleaned of the remaining honey with fishing tools.
Processing food
Tai chimpanzees crack open nuts with rocks, but there is no record of Gombe chimpanzees using rocks in this way. After opening nuts by pounding with a hammer, parts of the kernels may be too difficult to reach with the teeth or fingernails, and some individuals use sticks to remove these remains, instead of pounding the nut further with the hammer as other individuals do: a relatively rare combination of using two different tools. Hammers for opening nuts may be either wood or stone.
Collecting water
When chimpanzees cannot reach water that has formed in hollows high up inside trees, they have been observed taking a handful of leaves, chewing them, and dipping this "sponge" into the pool to suck out the water. 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
There are few reports of gorillas using tools in the wild. Western lowland gorillas have been observed using sticks to apparently measure the depth of water and as "walking sticks" to support their posture when crossing deeper water. An adult female used a detached trunk from a small shrub as a stabiliser during food gathering, and another used a log as a bridge. One possible explanation for the absence of observed tool use in wild gorillas is that they are less dependent on foraging techniques that require the use of tools, since they exploit food resources differently from chimpanzees. Whereas chimpanzees and orangutans feeding involves tools such as hammers to crack open nuts and sticks to fish for termites, gorillas access these foods by breaking nuts with their teeth and smashing termite mounds with their hands.
Captive western lowland gorillas have been observed to threaten each other with sticks and larger pieces of wood, while others use sticks for hygienic purposes. Some females have attempted to use logs as ladders. In another group of captive gorillas, several individuals were observed throwing sticks and branches into a tree, apparently to knock down leaves and seeds. Gorillas at Prague Zoo have used tools in several ways, including using wood wool as "slippers" when walking on the snow or to cross a wet section of the floor.
Orangutans
Orangutans were first observed using tools in the wild in 1994 in the northwest corner of Sumatra. As with the chimpanzees, orangutans use tools made from branches and leaves to scratch, scrape, wipe, sponge, swat, fan, hook, probe, scoop, pry, chisel, hammer, cover, cushion and amplify. They will break off a tree branch that is about 30 cm long, snap off the twigs, fray one end and then use the stick to dig in tree holes for termites. Sumatran orangutans use a variety of tools—up to 54 types for extracting insects or honey, and as many as 20 types for opening or preparing fruits such as the hard to access Neesia malayana. They also use an 'autoerotic tool'—a stick which they use to stimulate the genitals and masturbate (both male and female).Anne E. Russon, Carel P. van Schaik, Purwo Kuncoro, Agnes Ferisa, Dwi P. Handayani and Maria A. van Noordwijk Innovation and intelligence in orangutans, Chapter 20 in Orangutans: Geographic Variation in Behavioural Ecology and Conservation, ed. Wich, Serge A., Oxford University Press, 2009 , p.293 There have been reports that individuals in both captivity and in the wild use tools held between the lips or teeth, rather than in the hands. In captivity, orangutans have been taught to chip stone to make and use Oldowan tools.
Orangutans living in Borneo scavenge fish that wash up along the shore and scoop catfish out of small ponds for fresh meals. Over two years, anthropologist Anne Russon observed orangutans learning to jab sticks at catfish to scare them out of the ponds and in to their waiting hands. Although orangutans usually fished alone, Russon observed pairs of apes catching catfish on a few occasions. On the island of Kaja in Borneo, a male orangutan was observed using a pole apparently trying to spear or bludgeon fish. This individual had seen humans fishing with spears. Although not successful, he was later able to improvise by using the pole to catch fish already trapped in the locals' fishing lines.