Anolis Cupreus: The Response of a Lizard to Tropical Seasonality

Abstract

Seasonal changes in the population ecology of Anolis cupreus, a sexually dimorphic lizard, were studied over a 2—yr period in a deciduous and riparian forest ecosystem in western Costa Rica. This tropical environment undergoes strong seasonal changes, including a 6—mo yr dry season during which maximum air temperatures, hours of daily sunshine, and heavy winds occur. Many aspects of the ecology of A. cupreus undergo striking seasonal changes in response to this climatic seasonality. Both sexes were sexually active for about 6 mo of the year, with the ♀ cycle coinciding with the wet season. Fat body cycles in both sexes were inversely related to the reproductive cycles. Males and ♀ ♀ attain sexual maturity at 1 yr or less, and the population apparently undergoes an annual turnover. Population density was high (> 1,200 anoles/ha) in the dry season, but in part because of changes in the structural habitat of ♂ ♂ and territorial behavior, density was much lower in the wet season. In the dry season social interactions were rarely seen, both sexes perched at or near ground level, and ♀ ♀. In contrast, in the wet season social interactions occupied a majority of the ♂ ♂ time as they defended territories and courted ♀ ♀. At this time of the year ♂ ♂ perched much higher than ♀ ♀ fed primarily on the ground; ♂ ♂ obtained at least half their food up to 6 m aboveground in the wet season. Because of seasonal changes in perch heights and size of prey items eaten, intrasexual (seasonal) values of place x food niche overlap were lower than intersexual values. The response of this anole to stressful climatic conditions is analogous to that of its Temperate Zone congener, Anolis carolinensis. Whereas A. carolinensis hibernates to avoid low winter temperatures, A. cupreus becomes inactive during periods of high winds and air temperatures.