BEHAVIORAL INTERFERENCE FOR PERCH SITES IN 2 SPECIES OF INTRODUCED HOUSE GECKOS

The introduced house geckos, Hemidactylus turcicus and Cyrtopodion sca brum exist in sympatry in Galveston, Texas. The nightly perch choices of each species in captivity were recorded, first in species-segregate d enclosures, then with species mixed. While segregated by species, PI . turcicus occupied vertical wails more frequently than ground or rock perches. Cyrtopodion scabrum perched predominantly on rocks. While mi xed in the enclosures, the proportion of individuals not visible incre ased independently for both species, while the proportion of both spec ies occupying their respective preferred perches decreased. Perch heig hts did not differ between species, regardless of whether the species were segregated or mixed in the enclosures. The observed changes in us e of space while in sympatry may be due to competitive interference be tween these two species, and may reflect the situation in Galveston, w here C. scabrum appears to be gradually displacing H. turcicus in area s near the docks, where these two species previously existed in sympat ry.