Variation in predator-induced behavioral changes in introduced and native populations of the invasive New Zealand mud snail (Potamopyrgus Antipodarum gray, 1843)

Predator detection and avoidance can be important factors determining the success of an introduced species. The New Zealand mud snail (Potamopyrgus antipodarum) exhibits avoidance behaviors when chemically detecting native piscine predators in New Zealand, and these behaviors appear specific to sympatric fish populations. Here we utilized three different introduced clonal populations of the New Zealand mud snail from North America, and various clones from New Zealand lakes, to examine the effect of a novel piscine predator, the blacknose dace (Rhinichthys atratulus), on behavior. Two of the introduced clones in North America are invasive (US1 and US2) while a third clone (US3) has not exhibited invasive tendencies. In a laboratory setting, we examined geotactic (vertical movement in response to gravity), photokinetic (differential speeds in response to light), and emergence behaviors of each clonal population in the presence and absence of a predator chemical cue. Geotaxis was measured by determining the vertical distance traveled in two minutes. Photokinesis was measured by quantifying the horizontal distance travelled in two minutes in light and dark conditions. Emergence time was determined by removing individuals from the water for five seconds and then replacing them in water and measuring the time to emerge from the shell. We found that the two invasive populations of the New Zealand mud snail (US1 and US2) detected and behaviorally responded to the novel predator utilizing positive photokinesis. The US1 population also showed some evidence of geotactically responding to fish odor. The introduced but likely non-invasive US3 population did not exhibit a detectable response to the odor of fish. Some evidence of photokinetic behavioral responses to the North American fish odor was also found in New Zealand native populations. Fish odor did not appear to influence the time it took for any population of snails to emerge from their shells. These results suggest that the ability to detect and respond to novel predators may be an important trait in the invasion success of New Zealand mud snails by potentially allowing snails to avoid novel predators.