Variação temporal na predação de ninhos de jacaré-açu (Melanosuchus niger, Alligatoridae) na Amazônia Central, Brasil

Abstract

In the Amazon floodplain, the nesting period of the black caiman (Melanosuchus niger) occurs in the dry season, when land areas are available. The incubation period can extend up to 90 days. The main threats to the success of nesting of black caiman are flooding and predation of nests. The main predators of black caiman eggs are jaguars (Panthera onca), tegu lizards (Tupinambis teguixim), capuchin monkeys (Sapajus macrocephalus) and humans (Homo sapiens). In this study, we investigated the relationship between predator attacks on nests and incubation period, and evaluated the influence of initial predation on subsequent predation in the Mamirauá Sustainable Development Reserve. We also evaluated the influence of presence of females near the nests and manipulation of nests on the occurrence of attacks. We compared results from data obtained with camera traps and vestiges left by predators on estimates of rates of predation by different predators. Egg predation was recorded in 32% of the 658 black caiman nests monitored for two years. Our results suggest that the probability of predation on black caiman eggs is relatively constant throughout the incubation period and that predation on eggs was lower when adults, presumably females, were present. The opening of nests and handling of eggs did not increase the number of attacks on black caiman nests. Nest opening by a predator appeared to increase the chances of a subsequent attack because most of the attacks on nests occurred soon after a predator first opened the nest. However, attacks by another species of predator do not appear tobe necessary to initiate attacks by any of the species of predator. Results based on camera traps and vestiges were generally similar, but of vestiges underestimates the number of species that attacked the nest in more than one predation event. This making the method ineffective for studies that seek information on all species of predators involved.