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A Clark’s nutcracker (Nucifraga columbiana) flies to the top of a pine tree and selects one of the many cones. She twists and pecks at the stem until the cone breaks free from the branch and, with one foot, holds the cone in the crotch of a branch. She then repeatedly hammers her long bill in between the scales of the cone. After forcing out one of the seeds, she tips her head back a bit, clicks the seed in her bill a few times, and closes her bill. A few minutes later, the shredded cone drops to the snow, the nutcracker having extracted several dozen seeds. Each time she closes her bill, the nutcracker makes a choice: she either swallows the seed or places it in a small pouch of skin under her tongue. The seeds placed in her pouch are destined for a site several kilometers away, where she buries them under a bit of dirt or leaf litter. In the autumn, she may bury 33,000 seeds in this manner, only to return to uncover them a few months later during the harsh mountain winter. This form of food storing or caching typifies an interesting and wide-ranging set of decisions faced by animals: intertemporal choices.
The term “intertemporal” choice refers to decisions in which the benefits associated with different outcomes occur at different times. For instance, for each seed, the nutcracker must choose between eating it now versus waiting to consume it in the winter. Often, there exists a trade-off between the size of the benefit and the cost (time delay), such that larger benefits accrue after longer delays. Thus, the decisions of interest are between obtaining immediate or short-term rewards and investing in a grander future.