Demographic and growth analysis of broad snouted caiman (Caiman latirostris) in a disturbed environment in southeastern Brazil.

Abstract

Crocodilian life history traits exhibit strong size and age dependence, which is determined, ultimately, by how fast individuals grow. Crocodilian population dynamics are dependent on environmental conditions such as local temperatures and hydrology. From February 2010 to October 2011 we conducted monthly spotlight surveys to study a broad-snouted caiman population at the Três Marias Hydro-electric Reservoir, southeast Brazil. A total of 12 spotlight surveys were conducted (17.3 to 48.0 km in length), and animals were captured, measured and marked whenever possible. Data were obtained on population size, sex structure, survival, distribution and growth. The number of caimans counted, including hatchlings, varied from 6 to 78 per survey. Marked individuals showed a growth rate that varied between 0.0 and 0.3 cm*day-1 SVL, and between -6.0 and 8.0 g*day-1 body mass. Polyphasic growth was associated with rainfall and water level, which in turn were associated with changes in temperature and diet. The species seems to be resistant to the ecological impacts of damming, an important conservation conclusion considering the large number of hydroelectric dams within the species’ range in Brazil.