Differences in growth and foraging behavior of native and introduced populations of an invasive crayfish

The competitive displacement of native by introduced species has often been attributed to differences in growth and behavior of the invader with its competitors. However, is the contribution of these traits to invasion success due to different competitor species between the native and introduced ranges or to differences among populations of the invader? Here we compared the growth and foraging behavior of the rusty crayfish (Orconectes rusticus) from its native and introduced ranges when competing with congeners from both ranges (O. cristavarius and O. propinquus, respectively). Our results indicated that O. rusticus from the introduced range grew significantly more than native O. rusticus and that there was no effect of competitor species on the growth of O. rusticus. Thus, the contribution of higher growth rates to the invasion success of O. rusticus was a result of population differences of O. rusticus in contrast to differences between congeners across both ranges. Foraging activity and recruitment to bait were higher in introduced versus native populations of O. rusticus when competing with O. cristavarius, but, not when competing with O. propinquus. Rather, O. propinquus significantly recruited to bait first when competing with either population of O. rusticus. However, 57% of the time that O. propinquus was first to find the bait, introduced O. rusticus aggressively pirated the bait from O. propinquus. In contrast, native O. rusticus were never observed pirating bait from O. propinquus. We suggest that this behavior may, in part, explain the higher growth observed in introduced populations of O. rusticus. The differences in behavior between O. rusticus populations depending on the competitor species may be due to behavioral flexibility that may drive higher growth rates in introduced populations of this species.