Scared to Death: Prolonged Exposure to Predator Chemical Cues
Increase Mortality in Wolf Spiders
The wolf spider Pardosa milvina shows effective antipredator behavior (reduced activity) in the presence of chemical cues (silk and excreta) from a larger syntopic species of wolf spider, Hogna helluo. We measured the effects of prey availability and prolonged exposure (21 days) to Hogna cues on Pardosa body condition and survival. We used a 3x4 factorial design (N = 225; 17-23/treatment) with three feeding levels (1 prey/wk, 4 prey/wk, or unlimited food) and four predator cue exposure levels (constant exposure to fresh Hogna silk and excreta, constant exposure to Hogna cues that were not renewed, intermittent exposure to fresh cues [intervals of 2 days with cues-2 days without], and no predator cues). We found that the presence of renewed or non-renewed predator cues significantly increased mortality of Pardosa relative to intermittent or no predator cue exposure. Feeding level did not significantly affect mortality. Both feeding level and predator treatment significantly influenced body condition over the testing period. Intermittent exposure to predator cues had no significant impact on body condition. Pardosa appears able to behaviorally compensate for periods of high predation risk when risk is temporally variable; however, prolonged exposure to predator cues may have indirect but lethal effects on prey. Indirect lethal effects may not be frequently observed under field conditions because of the mitigating effects of temporal variation in predation risk. Nonetheless, our results suggest that the long-term influence of predator-induced stress on prey survival may often be underestimated.
