Habitat preference and movement of the wolf spider Pardosa milvina)
We measured habitat preference of the wolf spider Pardosa milvina across different developmental stages (juveniles, subadult males, subadult females, adult females, adult females with egg sacs, adult females w/ spiderlings) within different crops (tilled corn, no-till corn, no-till soybean, and a fallow field). We used three methods to measure preference: field censuses, laboratory habitat choice tests, and direct observations of spider movement within different tillage and crop types. Within a 10.5 ha strip crop system, we censused P. milvina within 0.5m2 rings from May 30-July 26, 2002 (N = 654). We also sampled at 0, 5, 10, 25, 50, and 100 meters from a hedgerow and quantified litter depth, plant density and meteorological variables. Spiders of all developmental stages preferentially avoided hedgerows. We found significant differences in distance from hedgerow, crop type, and tillage practice in spider density. Spiders at different developmental stages also exhibited significant differences in habitat preference. We also measured time spent in one of two habitat types for all developmental stages and both sexes under laboratory conditions. All developmental stages and both sexes preferentially avoided bare soil, but the strength of preference was significantly different by age and sex (N = 438). Nine 2 m2 plots were constructed containing three different substrate types; bare soil, grass, and no-till soil with corn stubble. Flags were placed every 20 cm forming a grid within each plot. Wild male, female, adult and subadult, spiders were caught, marked, and placed within the center of each plot (N = 180). We then measured time to leave the plot, speed, distance traveled, and space use. We found a significant difference is preference by substrate type, as well as a difference in movement depending on sex and age of the spider. Results indicate that P. milvina habitat preference varies by sex, age and reproductive status of the spider and that tillage practices greatly effects spider density and movement.