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An old joke circulates among animal behavior instructors. One can, the joke goes, divide the topics of animal behavior into four Fs: fighting, fleeing, feeding, and reproduction. This somewhat tired joke carries considerable truth. Animals behaving in nature surely must make decisions about conflicts, predator avoidance, feeding, and mating. Male crickets, for example, are notoriously combative. Studies have shown, however, that they escalate fights in some situations and retreat to fight another day in others (Beaugrand, 1997; Parker, 1974; Parker & Rubenstein, 1981). Squirrels, like many small animals, respond to the presence or absence of protective cover; for example, they will carry large food items into the safety of the bushes to consume them but eat small items immediately (Lima, Valone, & Caraco, 1985). Female widow birds prefer males with long tails, and evolutionary theorists have argued that tail length correlates with male quality (Andersson, 1982, 1994). So a female confronted with a short-tailed male faces a dilemma: mate now or keep looking. Notice that in all of these choice situations, time complicates the animal’s problem: Risk injury by fighting now or retreat to fight later; stay exposed to possible predation or invest time in moving to a safer place; settle for the short-tailed male or keep looking. Each of these situations, and indeed virtually any naturally occurring choice situation one can imagine, is an intertemporal choice problem. We define these as choice situations in which an animal’s alternatives vary in the time at which the animal realizes consequences and in the quality of those consequences once the animal secures them.
Although intertemporal choice applies to many domains (and all four Fs), we need to focus on a specific situation to make scientific headway, and for virtually all behavioral ecologists interested in intertemporal choice that focal situation is foraging. We can observe animal foraging choices easily (e.g., animals eat more often than they reproduce), and we can manipulate the time and magnitude of foraging options much more easily than we can manipulate mate quality or predation risk. Moreover, we have a large base of theoretical and empirical results that help us frame the intertemporal choice problem in the context of animal foraging behavior. Foraging is not only a convenient topic but also a fundamentally important one; actively seeking food is a basic part of animal existence that deserves our attention. In the first part of this chapter, we focus on adaptive aspects of intertemporal choice in animal foraging behavior, and especially on the problem of impulsivity, which we see as a central problem in intertemporal choice. In the second part of this chapter, we take a broader perspective, including domains other than food and extending beyond impulsivity to a more encompassing view of intertemporal choice. Within this general view, we explore the adaptive nature of impulsivity.