Regional differences in growth rates of Orinoco crocodiles (Crocodylus intermedius) from the Venezuelan Llanos.

Populations of the Orinoco crocodile (Crocodylus intermedius) have not recovered from past exploitation, and current abundances cannot be used for assessing the suitability of habitats they occupy. Growth constitutes an alternative way of assessing habitat quality. Since 1990, more than 9000 captive-reared Orinoco crocodiles have been released into the Venezuelan Llanos. In the present study, the growth rates of 127 recaptured crocodiles from different regions were compared. All individuals from Middle Cojedes and the Aeolian savannahs grew slower than expected by the von Bertalanffy model, whereas individuals from Caños in the Apure floodplains grew faster than expected. These inferences are corroborated with growth rate measurements for crocodiles under four years of age, which were lowest in Middle Cojedes (average of 14.1 cm/ year) and highest at Caños (43.3 cm/year). Low growth rates can be explained by habitat deterioration due to human activities, and high growth rates in the Caños support that the lower reaches of whitewater rivers offer favourable conditions for the species. Crocodiles in high quality habitats may reach sexual maturity in six years, whereas more than a decade is required in poor-quality habitats. [ABSTRACT FROM AUTHOR]