Differences in memory capabilities in invasive and native crayfish.

The memory capabilities of individuals of four species of crayfish (two invasive species and two native species) were tested in the laboratory. Individuals of the invasive Orconectes rusticus and the native O. virilis were tested in Michigan, and the invasive Procambarus clarkii and the native Austropatmobius pallipes were tested in Italy. Following pairing of conspecific alarm odour and a novel odour (goldfish odour), individuals were tested one day, one week, and either three weeks later (Italy) or two and four weeks later (Michigan) for inhibition of feeding responses by goldfish odour. In all four species, exposure of animals for just two hours was sufficient to establish an association between the novel odour and elevated predation risk. In both species pairs, individuals of the invasive species showed evidence of retention of the learned association longer than did individuals of the native species. The results are consistent with the general hypothesis that invasive species have a greater capacity for behavioural plasticity.