Juvenile crab spiders (Mecaphesa asperata) use indirect cues to choose foraging sites

Abstract

Direct assessment of food resources may be unreliable if those resources fluctuate or are not easily detected. Foragers under such conditions may instead use indirect cues to assess the quality of potential foraging sites. Young individuals may be particularly likely to use indirect cues to compensate for their inexperience and to reduce assessment costs. We investigated the cues juvenile crab spiders (Mecaphesa asperata) use when selecting foraging sites. First, we examined whether spiderlings' site preference was influenced by prey abundance, a direct cue of site quality. We next investigated whether juvenile crab spiders assessed potential sites using indirect cues, including flower quality, cues left by conspecifics, or conspecifics themselves. We found spiderlings did not use prey abundance to assess foraging sites, but instead used indirect cues when choosing where to forage. Spiderlings preferred sites that would attract larger numbers of their arthropod prey, choosing blooming inflorescences over both senescing inflorescences and inflorescences with buds. Hungry spiderlings, unlike individuals that had recently fed, also used cues left by conspecifics, preferring sites on which a conspecific had previously foraged. Finally, spiderlings avoided sites with larger numbers of conspecifics, but were attracted to sites with relatively low abundances of conspecifics, indicating that spiderlings are able to weigh the possibility of improving their foraging success by joining conspecifics against the potential costs of being in larger groups. We show here that young, relatively inexperienced animals do not always directly assess prey abundance when choosing foraging sites, but that these individuals are capable of detecting and using a variety of indirect cues to evaluate foraging site quality.