Captive Asian elephants have often been observed to use branches to swat flies. The branches are modified by shortening and removing side branches. Recently, wild Asian elephants have been seen demonstrating the same tool-using and toolmaking behavior.
The environment must possess two characteristics in order for tool use to evolve among a population of animals. First, there must be some evolutionary advantage in tool use. For example, the animal must be more successful at finding food, avoiding predators, or reproducing. Second, objects in the environment that will make useful tools must be available. Chimpanzees use twigs, wasps use small stones, and finches use cactus spines.Without access to these objects, the tool-using behavior would never evolve. The following examples illustrate how Egyptian vultures, woodpecker finches, green herons, and chimpanzees gained an evolutionary advantage from tool use.
Egyptian Vultures
An Egyptian vulture, Neophron percnopterus, has been observed breaking open ostrich eggs, too hard to open by pecking, by throwing a stone held in its beak at the egg shell. The bird's aim is quite good. According to reports by Jane Goodall, the vultures will wander as far as 50 meters (165 feet) from the egg to find a suitable rock.
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