Impact of food predictability on social facilitation by foraging scavengers

Foraging individuals may use either personal information derived from their own previous experience or social information obtained vicariously. When resources are unpredictable, personal information may be of little use, as illustrated by Gyps vultures that historically rely on unpredictable carrion and social foraging strategies. But human activities may increase resource predictability, for example, the implementation of feeding stations makes food patches more spatially predictable for scavengers. We explored the impact that different levels of resource predictability might have on the use of personal or social information in foraging strategies. We developed an individual-based spatially explicit model of foraging Gyps vultures in the presence of feeding stations to explore different search strategies as well as different management scenarios. Changes in food predictability may affect social foragers, and their adaptation to new conditions is likely to depend on their ability to use different types of information. In our work, when resources were predictable, individuals using previously acquired personal information ("Trapliners") were more successful than those relying on social information ("Networkers"). The situation was reversed when there were few predictable resources. Local enhancement, a social cue from feeding conspecifics that was available to all strategies, did not benefit Trapliners who were more aggregated than Networkers and suffered more strongly from competition on the food resources. In large populations, even when some resources were predictable, Trapliners were not more successful than other strategies.