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Field Observations of Agonism in the Crayfish, Orconectes rusticus: Shelter Use in a Natural Environment

Martin, Arthur L. III., Moore, Paul A.
Ethology 2007 v.113 no.12 pp. 1192-1201
benthic organisms, crayfish, foods, habitats, lakes, limestone, predators
Crayfish are aggressive animals that compete to acquire resources such as shelters, food, and mates. Shelters are a primary resource that crayfish use for protection from conspecifics and predators. Despite the importance of this resource, no field research has been performed that studies the acquisition and control of this resource. The present study examines shelter use in a natural habitat and the impact that shelter ownership has on the intensity and outcome of agonistic encounters. A stationary underwater camera was used to observe crayfish, Orconectes rusticus, shelter use and agonistic interactions in a natural lake environment. These shelters were formed naturally in iron outcroppings found on the limestone and detritus benthos. Crayfish activity and shelter use was found to be dependent upon a circadian cycle with most of the shelter use occurring during the morning to early afternoon (05:00-13:00 hours). Agonistic encounters in the presence of shelters resulted in short, low intensity interactions. Interestingly, fight outcomes were not significantly affected by shelter ownership, but were primarily determined by size differential of combatants. This outcome may be due to the prevalence of shelters within this habitat. Contrary to laboratory studies, these results indicate that shelter ownership may not be an important factor in determining resource-holding potential in some habitats.