Effects of habitat complexity on giant water bug ( Belostoma ) functional response to rams-horn snail prey ( Helisoma )

Outcomes of predator–prey interactions depend on biotic and abiotic factors. Habitat complexity, for example, mediates predator functional response type and parameters (attack rate and handling time). However, the relationship between habitat complexity and functional response varies across ecosystems. We assessed interactions between the giant water bug, Belostoma sp., and its prey, rams-horn snails, Helisoma trivolvis , across four prey densities ( N = 2, 4, 8, 16 snails) and three habitat complexity levels (No-complexity, Low-complexity, High-complexity) to understand how complexity affected the functional response. We also tested effects of predator and prey body size on number of prey killed. Belostoma exhibited a Type III functional response in all habitat complexity treatments. Attack rate tended to increase with increasing complexity. Handling time was different among treatments, being lowest in the No-complexity treatment and highest in the Low-complexity treatment. Belostoma body size was positively related, while Helisoma body size was inversely related, to the number of Helisoma killed. We show habitat complexity does not affect the shape of predator functional response but impacts response parameters in the Belostoma–Helisoma system. We reaffirm that attack rate, handling time, and mortality outcomes for prey within predator–prey interactions are affected by abiotic factors through habitat complexity.