Variation in native crayfish agonistic response to the invasion of the rusty crayfish Orconectes rusticus (Girard, 1852)

The consequences of biological invasions warrant continued research on the mechanisms underlying the spread of exotic species, yet interspecific behavioral interactions are largely overlooked as a contributing factor or consequence of introductions of exotic species. Our study evaluates how native crayfish species, Cambarus bartonii (Fabricius, 1798) and Orconectes propinquus (Girard, 1852), respond behaviorally to the invasion of the rusty crayfish, Orconectes rusticus (Girard, 1852) in the Upper Susquehanna River Basin, NY, USA using experiments in a semi-natural setting. We found significant effects of species, sex, year, novelty to invasion, and abiotic environment on the proportion of time native crayfish species exhibited agonistic behavior toward invading rusty crayfish. Cambarus bartonii females were generally more aggressive than males, particularly in year two, but the opposite was true for O. propinquus as males were more aggressive than females. Behavioral variation in recipient crayfish communities is a potential mechanism influencing the spread of introduced crayfishes although future study is necessary to assess the relative extent of such influence. The mechanisms driving the spread of invasive species are clearly complex and interactive, but the development of effective management plans is limited by the completeness of our understanding, which thus far has been lacking a substantial ethological component.