Many of the most flexible examples of tool use in animals come from primates (the order that includes humans, apes, and monkeys). For example, many wild primates use objects to threaten outsiders. But there are many examples of tool use by other mammals, as well as by birds and other types of animals.
Tools are used by many species in the capture or preparation of food. Chimpanzees
use sticks and poles to bring out ants and termites from their hiding places. Among the
most complex tool use observed in the wild is the use of stones by Ivory Coast
chimpanzees to crack nuts open. They select a large flat stone as an anvil (a heavy block
on which to place the nuts) and a smaller stone as a hammer. Stones suitable for use as
anvils are not easy to find, and often a chimpanzee may carry a haul of nuts more than
40 meters to find a suitable anvil. The use of tools in chimpanzees is especially interesting
because these animals sometimes modify tools to make them better suited for their
intended purpose. To make a twig more effective for digging out termites, for example,
a chimp may first strip it of its leaves.
Surprisingly, there is also a species of bird that uses sticks to probe holes in the search
for insects. One of the species of Galapagos finch, the woodpecker finch, picks up or
breaks off a twig, cactus spine, or leaf stem. This primitive tool is then held in the beak
and used to probe for insects in holes in trees that the bird cannot probe directly with its
beak. Birds have been seen to carry twigs from tree to tree searching for prey.
Tools may also be used for defense. Hermit crabs grab sea anemones with their claws
and use them as weapons to repel their enemies. Studies have demonstrated that these
crabs significantly improve their chances against predators such as octopus by means of
this tactic. Also, many species of forest-dwelling primates defend themselves by throwing
objects, including stones, at intruders.
【題組】50. Forest primates and certain sea animals are mentioned in the passage as examples of animals that use tools for
(A) self-protection
(B) food preparation
(C) hunting prey
(D) building nests or home plants grow.
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