The Consequences of Being Territorial: Spiders, a Case Study

Abstract

The potential for energy-based territoriality to limit population numbers is demonstrated here for a population of the desert spider Agelenopsis aperta (Gertsch). Enclosure experiments run on groups of spiders subjected to different feeding histories and representing two different populations demonstrate that territory size is a fixed characteristic of specific populations which is not influenced by temporal changes in prey abundance or in the numbers of competitors present. Data are presented which further show that territory size is adjusted over evolutionary time to lows in prey availability (times of greatest stringency). The inflexible nature of territorial behavior resulted in the saturation of one habitat offering a limited number of adequate web sites. Removal experiments showed that approximately 35% of the population occupying this habitat in 1978 existed as floaters. Floaters suffered marked daily losses in fitness relative to the gains exhibited by territory holders (measured as changes in bod...