Meeting Abstract

P1.60  Thursday, Jan. 3  The effects of prey availability and conspecific density on emigration in Pardosa milvina WRINN, K.M.*; SCHMIDT, J.M.; RYPSTRA, A.L.; Miami University; Miami University; Miami University, Hamilton wrinnkm@muohio.edu

Optimal foraging theory focuses on the decisions made by individuals concerning whether to stay in a particular patch and feed or to move on. These choices may be mediated by factors such as the amount of food in a patch, distance between patches, and the hunger of the individual, as well as presence of potential competitors or predators. We measured the effects of two of these factors, prey availability and competition (conspecific density), on emigration of the wolf spider Pardosa milvina. This species is commonly found in high densities in agroecosystems across the Midwest. Experiments were conducted in soybean fields and consisted of four groups, 1) no prey, low spider density 2) high prey, low spider density, 3) no prey, high spider density, and 4) high prey, high spider density. The appropriate combinations of prey and marked spiders were placed in circular metal enclosures (1m diameter) with tiny holes to allow emigration into pitfall traps outside. Twenty-four hours later, the number of spiders remaining in each enclosure was recorded along with the number of individuals that had tried to emigrate. Results showed that lack of prey increased the proportion of spiders emigrating. However, density of conspecifics had little effect on emigration. This indicates that prey density may be a driving role in emigration of these spiders in the agricultural fields, while competition (conspecific density) is secondary.