Evaluation of population status of Caiman crocodilus (Linnaeus, 1758) in Caño Negro Wildlife Refuge started in 1986. However, only information related with abundance and size of the population is known. The objective of this study was to evaluate population structure and sex ratio of C. crocodilus. We captured 145 caimans in 22 nocturnal spotlight surveys from May/2004 to May/2005. Most of caimans were less than 60 cm in length and between 150 to 180 cm. The average sex ratio was 1:6.06 female/male, being one of the highest differences reported for this species. If this sex ratio persists, there is going to be a decrease in the population viability in a short and long term period.
Caiman crocodilus; Population structure; Sex ratio; Caño Negro; Costa Rica
