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Kansas State University

 

Konza Prairie Biological Station

 

Long Term Ecological Research

 

 

Jesus E. Gomez

2007 REU Student from the University of Puerto Rico at Humacao, PR

Title:
Hide-and-seek among wolf spider and grasshoppers: applying ecology of fear theory  to invertebrates [poster]

Abstract:
The past study was realized at Konza Prairie Biological Station at Kansas in which the ecology of fear theory used to describe the nonlethal interactions between major vertebrate carnivores and their prey. The theory was applied to spider (Lycosidae) and grasshoppers (Acrididae) community interactions. The goals of the past study were to determine if spider presence alters the spatial distribution of grasshoppers, to determine variability in grasshopper and spider density among sites, and their relationship to one another. We predicted that grasshoppers will feed more in areas with a lower predation risk, but that vegetation structure would affect the spider and grasshopper community interactions and abundance. The Ecology of Fear predicts that spider abundance should alter grasshopper feeding.  Spider abundance was determined using pitfall traps at nine sites.  Body sizes were measured to the nearest mm and each spider was identified to Family, Genus and Species level. Grasshopper densities were determined with ring count transects, and feeding distributions were measured using bioassays plot inside the spider pitfall trap plots. Vegetation biomass was determined for five 0.2 m2 clip plots (forbs & grass). Our results show that there is no relationship between vegetation biomass and spider or grasshopper density. The negative relationship between grasshopper and spider density suggests that biotic interactions are important. Spatial distribution of feeding by grasshoppers was influenced by spider density. The spatial feeding distribution of grasshoppers within the plot followed predictions of the Ecology of Fear.