2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM

Paper No. 7
Presentation Time: 9:30 AM

Shared Responses to Resource Heterogeneity and the Origins of Foraging Behavior

KOY, Karen, Earth and Environmental Science, University of Illinois at Chicago, 845 W. Taylor Street, m/c 186, Chicago, IL 60607 and PLOTNICK, Roy, Earth and Environmental Sciences, Univ of Illinois at Chicago, 845 W. Taylor St, Chicago, IL 60607, LovleAnjel@hotmail.com

This study was designed to test the hypothesis that variations in foraging ichnofossil morphology are largely a response to spatial patterns in the resource environment. Modern organisms which forage amongst patches, such as Antarctic petrels, pocket gophers and rattlesnakes, have two distinct modes of movement: within-patch and between-patch movement. These different movement styles likely result from a difference in the cost-benefit balance an organism experiences while foraging. Within-patch movement occurs as a forager exploits the resources within a patch, and can take the form of complex spiraling or meandering movements termed area-restricted searching. Between-patch movement represents the non-directed or directed movements as a forager travels from one patch to another, whether or not it has detected and oriented towards a new patch. It consists of longer, straighter paths and prevents a forager from retracing its steps as it searches for a new patch to exploit.

Three different invertebrate species (pond snails, shore crabs, and soil nematodes) were placed within an arena with a single patch of food. All three invertebrates shared similarities in movement styles, and exhibited a difference between within- and between-patch path morphologies. The foragers' pathways within a patch are consistent with area restricted searching. Within-patch movement often resulted in spiraling and meandering pathways. Paths between patches more closely resemble a straight line, with longer paths between turns and smaller turns than within-patch movements. That these behaviors are shared by disparate invertebrate and vertebrate taxa indicates that the behavior is strongly selected for and may have evolved early in metazoan evolution.