Levels of predation and genetically based anti-predator behaviour in the spider, Agelenopsis aperta

Abstract

Two populations of the spider, Agelenopsis aperta, experience markedly different levels of avian predation. Although there is no measurable level of avian predation on this species inhabiting a grassland habitat, estimated bird predation on A. aperta in a riparian (woodland) habitat rangesfrom 15 to 86% of the local population per week. Population variability in anti-predator behaviour was tested in an experiment using large amplitude vibrations in the web to simulate a predator. Individuals from the respective populations were tested at their web-sites in the field and second-generation individuals reared in the laboratory were tested in the laboratory for their responses to this stimulus. In both the field and laboratory, significant population differences were observed in the latency to return to a foraging mode following retreat into the protection of the web-funnel. The population exposed to predation pressure by birds exhibited the longer latency to return. Within this population, moreover, latency to return to a foraging mode covaried at an individual level with latency to respond to prey encountering the web-sheet.