Ritualized male–male combat resulting from intraspecific food competition in three Agkistrodon species

Abstract

Male–male combat occurs in many snake species and is often thought to result from competition for mates. We argue a more thorough assessment of the contexts in which combat occurs is warranted for snakes. We made field video observations of Agkistrodon conanti in central Florida, A. piscivorus in eastern North Carolina, and A. contortrix in eastern Kentucky. These observations were made in frequently used foraging sites; near drying ephemeral ponds in Florida and North Carolina and in a forested area with abundant emerging cicadas in Kentucky. In all three populations, males engaged in ritualized combat. In four instances, a variety of lines of evidence including season, local food resource abundance, local female abundance, and postcombat behaviors all indicated that access to food resources, rather than mating opportunities, was the catalyst for agonistic behavior. Behaviorally, food-induced combat appears nearly identical to mating-induced combat. Simplistic assumptions about the environmental contexts that induce combat may lead researchers to make inaccurate conclusions concerning the duration of the breeding season and the frequency of intraspecific competition for food in snake species. We outline a rigorous set of criteria that should be used to determine the context of male–male combat bouts. Videos showing the examples of combat discussed are available at http://www.momo-p.com/showdetail-e.php?movieid=momo231230ac01a, http://www.momo-p.com/showdetail-e.php?movieid=momo231230ac02a, http://www.momo-p.com/showdetail-e.php?movieid=momo231228ap01a, and http://www.momo-p.com/showdetail-e.php?movieid=momo231230ap01a.