Time scales of associating food and odor by predator communities in the field

Many animals use volatile chemicals to detect and locate their food, but they frequently have to cope with a large variation in volatile blends associated with food. It has often been suggested that they do this by learning the association between odors and the presence of food. Indeed, associative learning was demonstrated for a range of animals under laboratory conditions and individuals usually take seconds to hours to modify their behavior. However, it is poorly understood at which timescale field populations and communities of animal species respond. We studied this by exposing egg batches of arthropod herbivores, half of which were combined with a volatile, to a community of natural enemies in the field. We used mint oil as a volatile blend, which we showed not to be attractive in the laboratory for 2 predators that commonly occur in the field. The predation of egg batches with volatiles in the field was initially slightly lower than that of batches without volatiles, indicating that the odor was not innately attractive to the natural enemies. However, relative to the controls, the predation of eggs associated with volatiles increased significantly over a period of 4-5 days. This suggests that individuals in the community of natural enemies associated the presence of eggs with the volatiles. We observed 3 different types of predation, indicating that various groups of predator species were responsible for predation in the field. Our results show that communities of animals rapidly associate volatiles with food in the field.