Predator/Prey Interactions

University of Wisconsin-Madison limnologist David B. Lewis conducted a study of predator prey interactions between freshwater snails and Crayfish.  His work was published in, Trade-Offs Between Growth And Survival: Responses Of Freshwater Snails To Predacous Crayfish (Lewis, 2001).  Lewis' snail of choice to study this interaction was Amnicola limosa. Two questions where posed by Lewis, one "whether the habitat association of snails is influenced by Crayfish, owing either to a behavioral response or to differential vulnerability among habitats. Second, I examine whether the growth of snails is affected by their responses to predation risk from Crayfish (Lewis, 2001)." 

Lewis observed that snails live more on bottom sediments where food is more plentiful when lakes lack abundant Crayfish populations (Lewis, 2001).  In lakes with abundant Crayfish populations snails tended to crawl up vegetation and other such elevated objects where food was scarce to avoid predation.  He also observed that more snails survived in habitats with abundant crawl up area than habitats with no or little crawl up area (Lewis, 2001).  His experiments backed his observations and he came to the conclusion that, "Crayfish likely impose a growth cost on snails through both direct and indirect pathways (Lewis, 2001)."  They do this by scaring snails vertically where they are not allowed to forage freely.

In one of his experiments entitled, "Differential Mortality", he compared A. limosa to Campeloma crassula (because of there similar morphologically but differing size, C. crassula being much larger) to, "Infer whether field patterns of snail distribution could derive from differential vulnerability among habitats (Lewis, 2001)."