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Evolution of Tool Use

While no single explanation can account for the appearance of all examples of tool use by animals, it seems probable that many examples could have originated as a result of accidents involving the performance of a pre-existing behavior pattern in a new situation. Animals that are unable to feed on food items that they could see but not capture and consume may have redirected their activities to naturally occurring objects near them, and if these activities proved to be rewarding, by allowing the animal access to a food source, the behavior would be reinforced and thus likely repeated .

In the case of darwin’s finches, a finch that is unable to secure insect larvae or adults that they could see but not reach in a deep crevice of wood may have performed redirected behavior in gathering twigs for building a nest in the breeding season. While still carrying a collected twig, a finch could be re-attracted to the crevice and start to jab the twig into the space, accidentally dislodging the insect. Thus the finch could in this way learn to associate the twig use with the reward of food and begin to habitually use tools in this type of situation. Other finches may have learned the same behavior independently, or from observing the original finch. While this theory is speculative, it could explain the development of tool-using behaviors in feeding animals in many different environments and situations.

It is interesting that animals that use tools seem pre-adapted for this behavior. Many primates have grasping hands, and birds have nimble beaks that can easily manipulate objects. Furthermore, both of these animals have behavioral patterns that involve object manipulation, such as nest building in the above example, as well as a high level of exploratory and learning abilities that can be seen as a foundation for tool use. It is important to note that an animal does not necessarily need to display insight in order to benefit from the observation of a companion, because it is often enough for an animal to simply attend to the activities of another and have its attention directed to some object or part of the environment it would have previously ignored by doing so.

Most species that learn to use feeding tools are social animals and/or have a period of close parent-offspring relationship that would facilitate learning from observation. All tool-using birds and primates feed in groups, suggesting that socially facilitated behavior could provide the basis for learned tool-use. Also, young animals that have been subject to selection pressures to learn a variety of things directly or indirectly from their parents may be especially likely to acquire tool-using behavior as a result of watching others .

Elephants

In regards to elephant physiology, the elephant brain seems very well suited to use and manipulate tools, based on similar studies on brain areas involved in tool use in humans. In fact, elephants have been cited as having the highest frequency and diversity of tool use of any non-primate species . Both African elephants (Loxodonta africana) and Asian elephants (Elephas maximus) possess a cerebellum that comprises approximately 18.6% of their brain, which is 1.8 times larger than in humans. This is mostly attributed to coordinated trunk movements that could aide in tool-use, as the cerebellum has also been associated with tool-use in human studies in regards to the fine manipulation needed to use tools. Elephants have a well-developed frontal and parietal lobe, which are the areas of the brain most associated with specific reasoning and spatial reasoning, respectively . Also, elephants have a disproportionately large temporal lobe. This is mostly linked to the great memory of elephants, but also plays a role in tool use and manipulation in studies with humans . These features of the elephant’s brain physiology, combined with the prehensile organ of the elephant’s trunk, make these animals particularly well-adapted for tool-use.

Elephants are very social animals.

Elephants show an ability to manufacture and use tools with their trunk and feet. This tool use is most associated with body care, specifically in the removal of ectoparasites and in thermoregulation. Both wild and captive Asian elephants use branches to swat flies or scratch themselves. Eight of 13 captive Asian elephants, maintained under a naturalistic environment, modified branches and swatted with the altered branch, indicating this species is capable of the more rare behaviour of tool manufacture. There were different styles of modification of the branches, the most common of which was holding the main stem with the front foot and pulling off a side branch or distal end with the trunk. Elephants have also been observed digging holes to drink water, then ripping bark from a tree, chewing it into the shape of a ball thereby manufacturing a "plug" to fill in the hole, and covering it with sand to avoid evaporation. They would later go back to the spot to drink.

Asian elephants may use tools in insightful problem solving. A captive male was observed moving a box to a position where it could be stood upon to reach food that had been deliberately hung out of reach. Also, elephants show plasticity in their tool-using behavior. While grazing on grass, an elephant will often pluck the clump of grass from the ground and strike the grass against its leg to remove excess dirt. If the elephant notices water nearby, however, it will use the pond to wash off the dirt instead. This adaptable response is illustrative of an intellectual process occurring in the elephant's brain, instead of a programmed result of genetics . Elephants have also been known to drop large rocks onto an electric fence to either ruin the fence or cut off the electricity.

Social learning is thought to be a key component of tool use in elephants. Elephants have an extensive developmental dependency on adults, and thus the opportunity for social learning is massive. In a study done by Hart et al., elephants of 9 and 18 months old showed different levels of tool-use aptitude. The 18-month-old elephant removed a side branch and was coordinated in using the branch to swat flies in comparison to the uncoordinated response of the 9-month-old. This difference in aptitude is thought to reflect the difference in the amount of time these young have had to learn .

In regards to the evolutionary significance of tool use in elephants, it is suggested that the tool use may compensate for a ‘lack of biological equipment’ . Large size and small surface area are good adaptive traits for aquatic animals in retaining heat (a recent ancestor of the elephant was likely a semi-aquatic animal like the Hippo), but it creates the problem of overheating for the terrestrial elephant, as well as providing little protection from flies and other skin irritants due to a lack of fur. These problems may have led to the development of behaviors for overall body care such as cooling, fly swatting, and scratching that all involve tool use. Biting by flies can incur fitness losses to the elephant in the form of loss of blood and the possible introduction of diseases. Therefore, tool use to prevent these fitness losses could have been favored by natural selection. Furthermore, an elephant’s particular feeding niche and the possession of the trunk as a prehensile organ may have predisposed these animals to tool-using behavior. Most of an elephant’s food, like long grasses, branches, and even whole trees, are potential tools in other circumstances. Interestingly, Hart et al. report that all elephants that were observed fly switching with branches were foraging at the time.

Bears

Moulting Brown bears in Alaska have been observed using rocks to exfoliate.

A brown bear.

In a current study at Washington State University, researchers have demonstrated that Grizzly Bears can manipulate objects in their environment to reach a food reward that is inaccessible to the bears otherwise. The experiment is conducted in two phases; the first phase involves observing whether a bear will use a properly positioned sawed-off tree stump to reach up and get the food reward down. Once the bear has been successful in the first portion of the experiment, the tree stump is then moved away from the hanging food reward and placed on its side. The bear must then move the stump into position with the proper orientation to gain access to the food, in order to show that it can manipulate inanimate objects in several steps to achieve a goal. While it’s still too early on in the study to reach scientific conclusions, several of the bears have proven to be adept at manipulating the tree stump to gain access to the food.