The Influence of Predator Mating Status on Chemically-mediated Antipredator Responses in the Wolf Spider Pardosa milvina
The wolf spider, Pardosa milvina exhibits effective defensive responses (reduced activity) in the presence of chemical cues (silk and excreta) from the co-occurring larger wolf spider Hogna helluo. Adult female wolf spiders vary considerably in their propensity to feed based on their age, mating status, and reproductive state. After mating, but before egg sac production, female lycosids typically become much more voracious and often double their body weight in preparation for producing a large egg sac. Also, silk-bound sex-pheromone production by females is high prior to mating, but decreases quickly after mating. We hypothesized that Pardosa may benefit by discriminating between chemical cues from a mated vs. unmated female Hogna, and exhibit defensive behaviors proportional to the level of risk. Using an automated video-tracking system (Noldus Ethovision), we measured Pardosa activity levels in the presence of silk and excreta from an adult female Hogna under four different mating treatments (N = 17/21/treatment): 1)Hogna cues from a female that was unmated, 2) cues from a female with one-insertion from a male during copulation, 3) cues from a female with two insertions, and 4) cues from a female that received a full mating. Pardosa activity level across these treatments was also compared to a control substrate lacking predator cues. Pardosa activity was significantly lower on most substrates containing Hogna cues relative to the control substrate. Substrates from fully mated females had the lowest activity level of all treatments but was not significantly lower than other treatments with female predator cues. Our results suggest that Pardosa cannot discriminate between mated and unmated adult female Hogna based on chemical information alone.
