Effects of learning on food selection and searching behaviour of deer

A review of feeding habits in black-tailed deer (Odocoileus hemionus columbianus Richardson) reveals considerable variation among animals, locations, and seasons. Since the processes affecting food selection are poorly understood, we explored the concept of optimal foraging as a means of predicting foraging behaviour of black-tailed deer. Food preference was initially determined for three foods under ad libitum conditions. We then studied the feeding behaviour of two deer using the same foods in a 0.5-ha enclosure and examined the effects of experience, density, and distribution of their preferred food on diet selection. When deer had to search for food, diet selection remained the same as ad libitum preference when preferred foods were abundant. Both animals became more efficient (intake per distance travelled) at finding preferred foods with increased experience in a particular food distribution. This was accomplished by repeating search paths that had been effective during previous trials. Consequently, performance was poor when the food distribution was changed. Under controlled conditions, memory of previous foraging events can play a role in food selection by deer. Description of a foraging bout as a static process ignoring its internal dynamics may be convenient but misleading.