Shillington, C.: Energy Metabolism and Thermal Ecology of Male Tarantulas (Araneae: Theraphosidae)

Male tarantulas of North America engage in intense mate-searching activity during the mating season. They compete for opportunities to mate and their mating success depends largely on rapid walking. Because they are ectotherms, their biological processes are dependent on environmental temperatures, which influences body temperature (Tb). Tb, in turn, has pronounced effects on metabolic rates and activities like locomotion and may directly influence mating opportunities. Temperature and energetic considerations are of particular interest because these factors help define the behavioral capabilities of animals and influence and organism’s interactions with its biotic and abiotic environment. Field studies of active male tarantulas indicate that they are primarily thermoconformers and restrict activity periods to times when ambient and ground temperatures are within their preferred range of body temperatures. Because of exceedingly hot day-time temperatures, males retreat below ground into abandoned burrows or holes during daylight hours and emerge around sunset. Times of retreat and emergence are temperature dependent although light intensity is also an important factor. Resting metabolic rates measured in both male and female tarantulas increased with temperature and, after adjusting for body mass, males had significantly higher metabolic rates than females between 20 and 35 degrees Celsius.