Mathematical Simulation of Thermoregulatory Behavior in an Orb-Weaving Spider

Abstract

1. In order to better document the thermoregulatory effectiveness of observed behaviours compared to other possible behaviours, we develop a model of interception of solar radiation. We demonstrate its use with data from a population of the orbweaving spider Nephila clavipes inhabiting a mid-altitude Mexican desert. 2. Nephila clavipes exhibits three behaviours that appear related to thermoregulation in this extreme climate: microhabitat selection, orb-web orientation and postural adjustments. 3. Large females more often built in open spaces without shade and small juveniles built within shrubs in shaded web sites. Webs built by large females tended to have a north-south orientation, whereas among small juveniles there was no correlation in web orientation. 4. Only individuals in unshaded sites exhibit postural thermoregulation, in which the spider's abdomen tracks the elevation of the sun. The simulation revealed that interception of solar radiation by large females was reduced by solar tracking, but that the north-south orientation of the orb did not reduce the interception of solar radiation relative to an east-west orientation.