Divergence in foraging and predator avoidance behavior across the geographic range of native and non-native crayfish

There is growing evidence that species' traits may diverge during biological invasions; however, we still lack a general understanding of how the invasion process affects behavior. We used a biogeographic approach to compare foraging and antipredator behavior across a reciprocal invasion (in which each species invaded the native range of the other) of virile (Faxonius virilis) and rusty crayfish (F. rusticus). We hypothesized that the invasion process would select for individuals that invest more in foraging and less in defense than their native counterparts. We used laboratory experiments to examine crayfish boldness, activity, and foraging voracity and mesocosm experiments to examine antipredator behavior in response to fish. Non-native virile crayfish (Indiana, USA) were less bold, active and voracious than native virile crayfish (Wisconsin, USA), and they exhibited more antipredator behavior. Non-native rusty crayfish (Wisconsin) were more active in mesocosms and exhibited less antipredator behavior than native rusty crayfish (Indiana). Combined, these findings suggest a growth/mortality trade-off. Counter to our hypothesis, relative investment in foraging versus predator avoidance differed across regions and was not consistently associated with native or invasive populations. Thus, the substantial divergence in behavior we observed may by driven by local adaptation.