Fine-scale substrate use by a small sit-and-wait predator

Substrate choice is one of the most important decisions that sit-and-wait predators must make. Not only may it dictate the prey available but also the cover for the predator which may conceal it from prey or its own predators. However, while on a particular substrate the behavior and use of that substrate may vary widely. When naïve, newly emerged crab spiderlings Misumena vatia (Thomisidae) occupied flowering goldenrod Solidago canadensis, their behavior differed markedly on inflorescences with relatively sparse and densely packed flower heads as well as on experimentally thinned and unthinned inflorescences. Initially, the spiderlings most often hunted at the thinned sites and hid among the dense flower heads at the unthinned sites, a difference that disappeared in all broods tested after 2--3 h, possibly because of the growing hunger of the initially concealed individuals. Prey capture (dance flies) in the thinned sites initially significantly exceeded that in unthinned sites but subsequently did not differ. However, spiderlings encountered their principal predator, the jumping spider Pelegrina insignis, significantly more often on unthinned than thinned inflorescences. Even though usage patterns initially differed strikingly, spiderlings did not differ in their rates of quitting the two types of sites. These results suggest a trade-off between foraging and predator avoidance that changes in response to increasing hunger over time. Copyright 2006.