NESTING ECOLOGY OF CAIMAN-CROCODILUS IN CANO-NEGRO, COSTA-RICA

Despite the widespread distribution of Caiman crocodilus fuscus (=chia pasius) in Central America, few detailed studies of its reproduction a re available. In northern Costa Rica, brown caimans nested in riverine forest adjacent to rivers or canals during the early wet season. Thir ty-five nests were located and measured in 1988-1989; detailed egg par ameters were measured from 17 clutches. Mean incubation temperature of nine nests averaged 31.8 C (30.5-32.8 C). Individual nest temperature s ranged from 29.6 to 36.0 C. Egg temperatures increased by 3 C in fiv e nests during the nesting season, but temperatures in four other nest s remained nearly constant. Flooding accounted for high embryonic mort ality by destroying entire nests; egg predation was minimal. Hatching occurred in September and October during high water levels when aquati c habitat was abundant. Delayed hatching of some nests suggests that a stimulus may be useful to initiate hatching. Typically, parent caiman s opened nests to release the young. Hatchlings formed sibling groups near the nest site and often remained together for over 1.5 years. Mou nd nesting was favored by the optimal conditions of the wet season in Cano Negro. Wet season nesting increases the availability of resources and suitable habitat to hatchling caimans. Abundant habitat during th e wet season enables hatchling to avoid predation and cannibalism. The predominant use of riverine forests for nesting by caimans in Cano Ne gro has important ecological consequences and management implications.