Prey of two species of jumping spiders in the field

Abstract

This is an observational study that describes the use of prey by jumping spiders (Phidippus audax and Salticus scenicus) in the field. Spider diets in the field were examined in terms of prey size and taxonomic family. Five percent of S. scenicus diet and 23% P. audax diet were comprised of other spider species. P. audax's predations on S. scenicus as well as S. scenicus feeding on juvenile P. audax were also observed (mutual predation). In addition, these spiders largely shared common prey, providing evidence of mutual intraguild predation in the field. To explicitly analyze the patterns of prey utilization in prey size, three likelihood models were constructed: 1) no difference in prey between large and small spiders, 2) disproportionate difference in prey size between spider size classes, and 3) proportional difference in prey size between spider size classes. Model selection indicated that both species of spiders utilized a distinct distribution of prey size based on their own size. P. audax's prey-size distribution was disproportionately different to their own size classes whereas such evidence was absent for S. scenicus. This difference between prey-size distribution is likely due to the morphological constraints of spiders (i.e., small spiders cannot attack large prey). Furthermore, large spiders included large prey as part of their diet in addition to small prey, rather than more exclusively shifting to forage on large prey. The field observation revealed potentially general and important species interactions that are not commonly explored in current intraguild predation (IGP) models.