THE INTERACTION OF TEMPERATURE, DISSOLVED-OXYGEN AND PREDATION PRESSURE IN AN AQUATIC PREDATOR-PREY SYSTEM

We examined the effects of the physical environment on the outcome of predatory encounters between tadpoles of the frog Rana clamitans and t he fishing spider, Dolomedes triton. These species co-occur in pond ha bitats that vary widely in dissolved oxygen and temperature. Water tem perature and oxygen levels have complex effects on the behavior of anu ran larvae. Behavioral responses induced by shifting physiological req uirements can increase the risk of predation on tadpoles. We experimen tally manipulated treatment levels of both dissolved oxygen and temper ature in trials conducted between individual predators (Dolomedes) and single prey (Rana). Environmental conditions had significant effects on the behavior of tadpoles that increased the risk of attack by Dolom edes. Under the low oxygen condition, more tadpoles were eaten, and th e total amount of time spent at the surface and the number of times su rfaced per minute were significantly greater. For Dolomedes, increased tadpole activity resulted in the increased expression of several pred atory behaviors. We found significant treatment and interaction effect s on the expression of both resting and ambush postures. In addition, survival analyses showed a significantly earlier expression of predato ry behaviors in decreased oxygen level treatments.