PARENT SESSION
Monday, August 7, 8:00-11:30 am
COS 3 - Foraging strategies and behavior
L-11, Lobby Level, Cook Convention Center
Presiders: R Whyte and L Hernández
Examination of the foraging tactics of a central place forager, Gopherus polyphemus, using correlated random walk models.
Halstead, Brian*,1, McCoy, Earl1, Stilson, Terri1, Mushinsky, Henry1, 1 University of South Florida, Tampa, FL
ABSTRACT- The gopher tortoise (Gopherus polyphemus) is a burrowing ectothermic herbivore in which sexual maturity is determined by size. Large adults are nearly immune from predation, but juvenile tortoises experience high predation rates. Attaining rapid levels of growth through consumption of high-quality forage plants is imperative for young tortoises. Juvenile tortoises spend most of each day in their burrows, emerging only occasionally to forage, and when they do emerge must balance foraging requirements and predation risk. A juvenile tortoise could employ foraging tactics to either forage close to its burrow, allowing rapid retreat into the burrow and risking insufficient forage consumption, or forage farther from its burrow, allowing sufficient forage consumption and risking increased exposure to predators. Foraging paths of juvenile gopher tortoises were observed in the field and analyzed using correlated random walk models. Because of the central place foraging habit of the gopher tortoise, the sinuosity of foraging paths was compared to the sinuosity of an optimal central place forager. Juvenile gopher tortoise foraging paths could not be distinguished from a correlated random walk, but mean squared displacement was greater than expected as individuals moved away from their burrows and less than expected as they returned. Sinuosity was less than expected for an optimal central place forager. Juvenile gopher tortoises travel a greater distance from their burrows when foraging than expected for a central place forager. Young tortoises may give up the security of remaining near their burrows during frequent foraging bouts to forage until satiation.
Key words: foraging tactics, correlated random walk models, Gopherus polyphemus