A novel environment drives modification of predator avoidance behavior in invasive rusty crayfish (Orconectes rusticus)

Background/Question/Methods

Biological invasions provide an opportunity to examine the importance of adaptation in determining strength of predator-prey interactions. A prey species may be adapted to coping with a predator in its native range, but new strategies may be required for avoiding the same predator in a novel environment. Rusty crayfish (Orconectes rusticus), native to streams in the Ohio River Drainage, were introduced to lakes in Wisconsin and Michigan in the 1960s. The native and introduced ranges have unique physical characteristics and biota which may impact interactions between crayfish and fish. Smallmouth bass (Micropterus dolomieu), voracious predators of crayfish, are native to both locations. Crayfish from invasive populations may display traits that are beneficial for spread, such as increased investment in reproduction and growth and decreased investment in predator avoidance. Therefore, we expected that invasive O. rusticus would spend less time in shelter, recruit to food more quickly, and be more active in the presence of fish than native O. rusticus. To test for behavioral differences, we collected adult crayfish from three drainages in Ohio and three lakes in Wisconsin and Michigan. We conducted experiments examining shelter use and food acquisition with fish absent, and time spent foraging with smallmouth bass present.

Results/Conclusions

Crayfish from invasive populations spent less time in shelter and were more active in the presence of smallmouth bass compared to crayfish from native populations. These behavioral responses suggest that rusty crayfish from native populations invest more in avoiding predation from fish than crayfish from invasive populations. More research is needed to determine whether predation risk is similar between the native and introduced ranges. In addition, crayfish from native populations recruited to food more quickly than crayfish from invasive populations. This result may be due to differences in food availability between the environments in the native and introduced range, or differences in interspecific competition. Behavioral differences observed between rusty crayfish from native and introduced populations suggest that novel environmental conditions can drive changes in predator-prey interactions that promote changes in anti-predator behavior. Whether these differences are genetically based or are due to behavioral plasticity will be addressed in future studies.