Effect of water level on insect-tadpole predator-prey interactions

Abstract

Predator-prey interactions are affected by environmental conditions. We examined the effect of changes in water level on the predator-prey interactions in a food web comprising of a top predator (dragonfly naiad), one mesopredator (backswimmer), and prey tadpoles of species that differ in microhabitat occupancy (neustonic and benthic). The results revealed that under high water level conditions (HWL), predators took longer to attack the neustonic tadpoles (Microhyla nilphamariensis) relative to the low-water-level condition (LWL). Dragonfly larvae mostly attacked the benthic tadpoles (Euphlyctis cyanophlyctis) when the water level was high. Nevertheless, under LWL, dragonfly larvae equally attacked both benthic and neustonic tadpoles. Interestingly, dragonfly larvae frequently attacked mesopredators (i.e., backswimmers) when they were presented together with neustonic tadpoles. These results demonstrated that changes in water level influence predator-prey interactions in the pond ecosystem where neustonic tadpoles faced lower risk under HWL. The reduction of water level favored the survival of benthic prey tadpoles. The presence of mesopredator (backswimmers) reduced the predation risk of neustonic tadpoles. These results help to understand how the differences in predation risks shape anti-predator responses in these prey tadpoles.