Anti-predator behavior of the wolf spider Pardosa milvina towards different sexes of the predator Hogna helluo.
The wolf spider, Pardosa milvina, reduces activity in the presence of chemical cues (silk and feces) from a larger predatory wolf spider, Hogna helluo. Female Hogna are significantly larger than males and may double their weight upon maturation whereas males do not. We predicted the following: 1) Female Hogna should present a greater predation risk to Pardosa than male Hogna, 2)Pardosa should reduce activity more in the presence of female rather than male Hogna chemical cues, and 3) Differences in Pardosa activity in the presence of male or female chemical cues should result in differential survival on each substrate when in the presence of a live predator. In the absence of predator chemical cues, Pardosa survived significantly longer in the presence of male Hogna compared to female Hogna. Hogna sexes were maintained on filter paper after which we presented the paper or a blank control to Pardosa. Pardosa decreased activity in the presence of chemical cues from either sex relative to the control and showed less activity in the presence of Hogna female cues relative to male cues. We assessed survival advantage of reduced activity due to male or female predator cues by placing Pardosa in containers previously occupied by a female Hogna, a male Hogna, or no Hogna. We then introduced a female Hogna into each container and measured predation latency. Pardosa survived significantly longer in the presence of female rather than male predator cues and had the lowest survival in the control treatment. We conclude that Pardosa show different levels of activity toward chemical cues of each sex of the spider Hogna helluo. We further suggest that Pardosa are mitigating potential fitness costs associated with antipredator behavior by exhibiting reduced activity relative to the perceived risk.
After Susquehanna: Leilani is currently at the University of Wurtburg in Germany.