Predator avoidance behaviour in response to turtles and its adaptive value in the freshwater snail Planorbella campanulata
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The Author(s) 2018. We investigated predator avoidance behaviours in the freshwater planorbid snail Planorbella campanulata when exposed to varied cues of risk of predation by turtles (Chelydra serpentina, Chrysemys picta marginata, Trachemys scripta elegans and Clemmys insculpta). Experiments were conducted to address the following questions: (1) What are the behavioural responses of these snails to turtles? (2) What chemical cues elicit responses? (3) How do predator and prey size affect prey vulnerability and reactivity to predators? (4) Are behavioural responses of snails effective in reducing predation by turtles? We found that P. campanulata snails responded to turtles by burying in the substratum. Snails buried occasionally (0-30%) in response to cues from nonforaging turtles, but frequently (30-98%) in response to actively-foraging turtles including a nonnative turtle species. Burial was not elicited by chemical cues from injured physid snails (Physella acuta). Small snails were more vulnerable to turtle predation and had a commensurately higher propensity to bury. Additionally, the propensity for snails to bury was related to turtle size. Smaller turtles stimulated more burial, perhaps due to the ungainly manner with which they ate snails, which released more snail injury cues compared to larger turtles. However, larger turtles consumed more snails. Buried snails suffered considerably less predation than snails forced to remain unburied. Therefore, the burial response appeared to be adaptive on balance, but imperfectly so.
