Resource partitioning of space and its relationship to body temperature in Anolis lizard populations

An index is introduced that allows both the use and availability of space as a resource to be quantified in a manner that parallels the way that the use and availability of food resources are quantified in community ecology. This index provides the 'resource axis' for space resources that pertains to the thermal implications of micro-climate. The index is called the Grey Body Temperature Index (GBTI) and it is the equilibrium temperature that an inanimate reference object attains in the space being quantified. For this study the inanimate reference object is a grey lizard-shaped object weighing 5 grams. Formulae to calculate the GBTI from measurements of air temperature, wind speed and solar radiation are derived from an energy balance equation. The technique is illustrated with Anolis lizard populations from Grenada and St. Kitts. It is shown that the two lizard species in Grenada partition space as a resource with respect to GBTI and that the two species in St. Kitts do not. The determination of the availability of space along the GBTI axis is illustrated for a site in St. Maarten.