Population status of Caiman crocodilus (Crocodylia: Alligatoridae) in Caño Negro, Costa Rica

Abstract

Caimans were censused by countig eyeshines with a headlamp from April to July 1986 in Caño Ne- gro National Wildlife Refuge, in northern Costa Rica. Estimated caiman population in the preliminary study area was 229 in the dry season and 23 in the wet season. Caiman density during the dry season was calculated in 3 sites as 83, 100, and 166 cai- mans/hectare. Total caiman population in the refuge was estimated in 1988 (2129) and 1989 (2438) during the dry season. Mean number of caimans per km of river was 53,0/km for 50,2 km of habitat in 1989. Percent of caimans that were visible during a count was 89,0 % (SD=6,62). We calculated the total caiman population at 3000 (2700-3300) within all transects in 1989. Caimans dispersed from dry season canals and lagoons into wet grasslands and swamps during seasonal flooding. Surveys used to estimate total caiman population should be made during the dry season when cai- mans are concentrated in open bodies of water. Annual fluctuations in caiman numbers occurred between survey sites. Variable nesting success probably caused the juvenile size class to greatly in- crease or decrease between years.