Do innate food preferences and learning affect crop raiding by American black bears?

American black bear (Ursus americanus) populations have been expanding geographically, in part because bears are learning to exploit agricultural landscapes where crops provide an easy and calorically rich foraging opportunity. Consequently, crop depredation has become a growing problem for farmers and wildlife managers. Bears may raid crops because of insufficient natural foods, a drive to increase body mass, or because they discovered the crop fields while looking for other foods. We tested whether simple food preferences, in the absence of other competing factors present in the wild, influence autumn foraging choices. We conducted food-choice trials with 9 captive black bears in 2010 and 2011 to assess preference among primary autumn food options found in northwestern Minnesota, USA, which is a site of present bear-range expansion. Food choices offered in the trials were acorns (preferred natural food), field corn (Zea mays), and 2 kinds of sunflowers (confection and oil; Helianthus annuus). We measured preferences among the 4 food types, through time, and between sexes. Males immediately preferred oil sunflowers, which provided the highest caloric input. Females exhibited a notable shift from the early trials, where acorns were highly preferred, to later trials where sunflowers were preferred, which was suggestive of learning. We postulate that in the wild, male bears, being more determined to enhance caloric intake, seek out whatever foods best meet this need, thus ranging farther and being less wary of threats or novel tastes. Females initially may be less willing to expand their diet with unfamiliar foods, but our experiments indicate that after some experience, they find anthropogenic foods increasingly appealing.