Foraging ecology of the cave cricket Hadenoecus subterraneus: Effects of climate, ontogeny, and predation (Kentucky).

摘要

Cave crickets (hereafter, crickets) periodically forage on the surface throughout the year. From 1995–2000, I examined the impact of abiotic and biotic factors on a hypothesized sequence of decisions crickets make before and during foraging bouts at three study caves in Mammoth Cave National Park. I found a significant positive correlation between numbers of exiting crickets and surface temperatures during cold months. Thus, foraging bouts are likely infrequent during cold months.; I used experimental food patches to examine where crickets fed and how much they consumed. Numbers of crickets feeding at my food patches were negatively correlated with average precipitation during the growing season. This suggested annual net primary productivity affects availability of crickets' natural food. In addition, crickets used my food patches more in winter than in summer. Crickets' highly distensible crop, when full, significantly affected jumping ability in large crickets but not small. Yet there was no significant correlation between crickets' food intake and food patch distance from cave entrances. This suggested crickets' perceived predation risk cost/benefit ratio when foraging were low.; Season significantly affected crickets' food intake. In summer, a significant reduction in their food intake and the total biomass of crickets at my food patches suggested interspecific exploitative competition occurred at one of my study caves. In winter, among all three study caves a significant positive correlation between total cricket biomass at my food patches and food intake suggested crickets' perceived predation risk was reduced with increasing numbers of feeding conspecifics; this may be due to the ‘dilution effect’.; Finally, I found cricket antipredator behavior is likely related to the frequency, density, and lethality of their predators. Crickets' egg-laying behavior is undoubtedly an evolutionary response to reduce high predation pressure from a cave adapted beetle that eats its eggs. However, cricket behavior was unaffected by orb-weaving spiders in caves which only occasionally catches them. At some caves entrances crickets run a gauntlet of cave salamanders when exiting/entering but their feeding was unaffected. On the surface, crickets' feeding was little affected by predation risk from white-footed mice even though mouse density increased near cave entrances.