Female state and condition-dependent chemical signaling revealed by male choice of silk trails

Male mate choice is predicted in systems with high costs of mating, as for those with male nuptial gifts and/or sexual cannibalism. We ask whether males of the nuptial gift-giving spider Pisaura mirabilis exert preferences for mates varying in their reproductive potential based on chemical information during mate search. Males were presented with binary trails consisting of silk lines and substrate-borne chemicals deposited while females were walking, from females varying in 1) body condition (high vs. low), 2) developmental state (subadult vs. adult), and 3) mating state (unmated vs. mated). If female chemical signaling co-varies with individual state, we expect males to choose trails of females that are 1) in higher body condition, indicating higher fecundity, 2) adults, which can successfully reproduce, and 3) unmated, to avoid sperm competition. We show that female signaling is condition-dependent, with males being more likely to follow trails of higher body condition females, but not dependent on female mating state. Males also tended to prefer trails of adults over subadults. Choice did not depend on male individual body condition. Our findings suggest costs to chemical signaling in nutritionally deprived females, often considered negligible, and their potential as reliable indicators of individual quality. Selection may favor male preferences for more fecund partners given the energetic investment nuptial gifts entail. Nutritional and reproductive benefits of multiple mating to females and high share of paternity for males, may instead select against signaling of female mating state, and/or male discrimination and choice.Animals can rely on chemical information for their mate choice decisions. We show that male spiders are able to discriminate the reproductive value of a potential partner based solely on trails consisting of silk lines and body odor, which are left by female while walking. Males preferentially followed trails of adult females in higher body condition, representing more fecund higher quality mates.