Effect of prey- and predator size on the capture success of an aquatic snake

Large aquatic snakes typically do not include small prey into their diet. This is hypothesized to be so because small preys are difficult to catch in an aquatic environment. Also an effect of snake size on capture success is plausible, with large snakes having a lower capture success then small snakes for similarly sized prey. We tested the effect of snake- and prey-size on the capture success of the specialized aquatic snake Natrix tesselata. No effect of snake size on capture success was found for the size range that was tested. Possibly size becomes only important from a minimum absolute size (larger than the maximal size tested in our study) onwards. Unexpectedly, Natrix tesselata needs fewer attempts to capture small fish. In contrast, N. maura, a congeneric more generalist species, needs fewer attempts to capture larger fish. A possible explanation for this conundrum lies in difference in the degree of specialization between these two species. An in-depth study of the hydrodynamics of this snake-prey system could provide ways to evaluate the importance of size effects.