Sexual Identification of Caiman latirostris Hatchlings by Cloacal Inspection

Abstract. Sexual identification of crocodilians is important in population studies and provides useful information for conservation and management plans and monitoring populations over time. It is possible to distinguish between male and female Caiman latirostris by cloacal palpation or eversion of the penis in individuals larger than 75 cm total length, but smaller animals possess a barely differentiable cliteropenis. In hatchlings, sex determination methods involve surgical examination, necropsy, or analysis of cranial dimorphism, which cannot be applied in the field. We classified hatchlings of C. latirostris by observing the color and shape of their genitals. The penis is a milky white organ with a rounded shape at the tip and a purple hue at the end, whereas the clitoris is shorter, whitish, and has a pointed end. The procedure was tested on hatchlings from three nests at the “Proyecto Yacaré” study area (Santa Fe province); half of the eggs of each nest were incubated at a constant temperature of 31°C (producing females) and the other half at 33°C (producing males). To observe the sexual organs by cloacal inspection, we used a modified instrument whose function during palpation is like that of a finger applied in large animals to evert the penis or clitoris. In the first days after hatching we correctly scored the sex of 80% of the individuals. The number of correct identifications was slightly lower for males than for females. This technique might be a useful tool for field studies, as it allows the sex of small caimans to be estimated in situ.