Passage I

Scientists conducted a study to examine the caching (storing food) and feeding behaviors of gray squirrels.

Prior to the study, acorns were collected from a park and sorted into types, first according to the species of tree they grew on—red oak, pin oak, or white oak—and then according to whether the acorn was undamaged, infested (contained insect larvae), or shelled (shell removed). Each acorn was stored at 2°C until the day it was to be used.

Study

The study was conducted over 75 consecutive autumn days. Beginning at the same time each morning, 225 acorns were placed, one at a time, at a given location in the park where the acorns had been collected. Each of the 9 acorn types was presented an equal number of times, and the order in which the acorns were presented was random. All the acorns were picked up by squirrels within 1 minute. Table 1 shows, for each acorn type, the percent of acorns that were cached, eaten, or rejected (dropped after being picked up) by the squirrels.

In addition, for each red oak acorn that was not rejected, the average distance (including both horizontal and vertical) the squirrel traveled before caching or eating the acorn was determined (see Table 2).

Adapted from M. A. Steele et al., “Caching and Feeding Decisions by Sciurus carolinensis: Responses to Weevil-Infested Acorns.” ©1996 by American Society of Mammalogists.