Fitness costs and benefits of chemically-mediated antipredator behavior in the wolf spider Pardosa milvina (Araneae: Lycosidae)
Abstract:Animals may exhibit a variety of defensive behaviors in the presence of predator chemical cues. Such behavior offers immediate fitness benefits but may also incur substantial foraging and reproductive costs. We measured shifts in space use (vertical climbing) by the wolf spider Pardosa milvina induced by chemical cues (silk and excreta) from a co-occurring predatory wolf spider Hogna helluo. We then measured foraging and reproductive costs as well as survival benefits of this behavior. For two weeks, we maintained mated adult female Pardosa in plastic containers with one of three treated peat moss substrates: (N = 25/treatment): 1) container previously occupied by a conspecific for three days, 2) container previously occupied by an adult Hogna for three days, and 3) peat moss devoid of either cue (control). We measured prey capture efficiency, body condition, egg sac production, egg sac weight, and egg number for individuals in each treatment. We also counted the number of Pardosa that survived and exhibited climbing behavior in the presence of a live Hogna with and without silk and excreta cues. Pardosa climbed container walls significantly more often in the presence of Hogna silk and excreta relative to other treatments. Pardosa exposed to Hogna cues coupled with live Hogna survived significantly longer than spiders that had no predator cues available. Pardosa placed in containers with Hogna cues, but no Hogna lost weight more quickly, ate fewer prey, were in poorer body condition, produced lighter egg sacs, and fewer eggs than spiders in control or conspecific treatments. Key words: Pardosa milvina, Hogna helluo, chemical cues, antipredator, wolf spider, Lycosidae, reproductive costs, survival benefits