HABITAT SELECTION BY SPHAERODACTYLUS NICHOLSI (SQUAMATA: GEKKONIDAE) IN CABO ROJO, PUERTO RICO

We studied habitat selection by the litter-dwelling gecko Sphaerodactylus nicholsi in the Cabo Rojo National Wildlife Refuge in southwestern Puerto Rico to determine how this small diurnal species exists in an apparently xeric habitat. We divided the 240 ha refuge into 956 quadrats each measuring 50 m × 50 m and selected 60 quadrats at random to search for geckos. The 60 quadrats yielded 33 discrete locations with sphaerodactylids that we called occupied sites. Occupied sites were located beneath the dense canopies of broad-leaved evergreen trees and were completely shaded. The average area of an occupied site was 103 m². We paired each occupied site with a nearby random site and compared relative sphaerodactylid density and habitat variables to determine features important in habitat selection. Occupied sites were in dense shade of evergreen trees and contained trees that produced large seeds or fruits; random sites commonly were exposed to sunlight, either directly or filtered through a thin deciduous canopy. Occupied sites had significantly lower daytime substrate temperatures, more leaf litter, less grass, less bare ground, and an order of magnitude more sphaerodactylids than the random sites. The four random sites with sphaerodactylids also had dense shade. Despite its small size, diurnal habit, and apparent vulnerability to dehydration, S. nicholsi thrives through selection of the scattered patches of relatively mesic environment within a xeric landscape.