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An experimental study of the predator-prey behavioral response race.
Sih, Andrew1, 1 University of California-Davis, Davis, CA
ABSTRACT- Space use by predators and prey, and in particular, patterns of spatial overlap between predators and prey are crucial elements of the predator-prey interaction. Numerous studies have shown that if prey are fixed in space (e.g., prey are immobile), then predators tend to forage in areas with more prey. The outcome is a positive spatial association between predators and prey. Conversely, numerous other studies show that if predators are spatially fixed (e.g., caged), then prey avoid areas with more predators. The result is then a negative spatial association between the two. Surprisingly few studies, however, have looked at the dynamics of the behavioral response race that occurs in the common, natural situation where both predators and prey can respond to the other. When should prey win the race (resulting in a negative spatial association between the two), and when should predators win (as indicated by a positive spatial association)? Here, I first review the basic idea of some extant game theory on this predator-prey behavioral race, and then present experiments examining this interaction involving treefrog tadpole prey (Hyla regilla) and predatory salamander larvae (Ambystoma tigrinum). The experiments address: 1) whether tadpoles in the absence of predators follow the matching prediction of simple ideal free distribution; 2) whether tadpoles avoid caged predators; and 3) the outcome of the race (i.e., the pattern of spatial association between tadpoles and salamanders) when both are free to respond to the other. Some results corroborated existing theory; however, some other results did not fit the predictions of existing theory. These suggest new, broader approaches to modeling the predator-prey race.
Key words: amphibian ecology, predator-prey behavior