Influence of prey availability on seasonal fluctuation in body condition in the wolf spider, Pardosa milvina (Araneae: Lycosidae)
2013
Schmidt, Jason M. | Harwood, James D. | Rypstra, Ann L.
Foraging by an organism varies over the season in response to environmental conditions. Predatory arthropods, such as spiders, are frequently in a food-limited state despite their polyphagous habits and may feed opportunistically to enhance rates of growth, survival and reproduction. We predicted that, to circumvent food limitation, spider foraging would be related to prey availability. We examined the extent to which body condition of spiders, a correlate of recent foraging, was related to prey availability and habitat type. Wolf spiders Pardosa milvina (Hentz 1844) were collected between May and October in two habitat types, corn and soybean fields. To assess changes in spider condition, we calculated and compared multiple body condition indices derived from morphometric measures of individual spiders. Prey abundance was monitored over the same period using a vacuum suction sampler. Body condition indices provided qualitatively equivalent results. Interestingly, juvenile males were in better condition than adult males, but the opposite was the case for juvenile versus adult females. Although the availability of potential prey generally increased over the growing season, changes in body condition fluctuated independently of prey, suggesting that Pardosa milvina have life history differences in foraging and demand for resources that may influence foraging decisions.
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