Tool-Using Performances as Indicators of Behavioral Adaptability

Abstract

Use of an object by animals as a functional extension of their limbs in order to obtain food or to facilitate some other goal seeking activity has quite commonly been reported as an especially significant indicator of intelligence or complex learning ability. The present review has selected well authenticated examples of tool-using behavior from different types of animal, such as wasps, crabs, birds, subprimate mammals, and nonhuman primates, and examined the context of their occurrence and the apparent complexity of performance involved. These performances have been concerned with: a) attainment of food; b) offensive or defensive use against predators or intruders; c) miscellaneous functions such as self-grooming, courtship, nest-building. Categories (a) and (b) contain by far the most instances, and (c) has very few indeed. The problem, in attempting a comparative analysis of such instances, is to evaluate the performance within the whole context of the animal's capacities and the way these are expressed in various ecological settings. The evidence cited is primarily from naturalistic studies, that from restrictive settings, such as Zoo or laboratory, being adduced only in emphasizing discrepancies. As an example, baboons have, so far, not been seen to demonstrate tool-using in the wild in their food-seeking behavior, but they do so readily when given the opportunity in captivity. They thus have a potential which their natural surroundings perhaps only rarely bring into action, whereas chimpanzees demonstrate their capacity for this kind of performance in diverse ways both in the wild and in capativity. Certain performances by nonprimate animals, such as the Galapagos woodpecker finch or the California sea otter, indicate that tool-using of a very effective, though presumably restricted, kind can evolve in animals having a narrow habitat range, and in whom, therefore, other significant aspects of adaptability may be missing. Further, from assessing the many instances of category (b) and the very few instances of category (a) in wild monkeys and apes, it was tentatively suggested that the emotional offensive-defensive type of tool-using might have had primacy in evolution over that of food-getting and the other miscellaneous instances. A review of this sort, with a suggestion of this kind, is put forward anyway chiefly as an attempt at clarification which may lead to much further detailed studies, experimental and naturalistic, of the animals in question. As always in describing complex behavior and in deriving models or inferences from the description, the profusion and confusion of terminology are difficult to sort out neatly or clearly. But the objective of this review will have been achieved if, in deliberately avoiding the use of controversial terms, it has been possible to show the need for a fresh research approach to the comparative study of behavioral adaptability in animals with a view to working out much more satisfactorily than at present the bearing that such evidence may have upon fundamental questions of human evolution.