Abstract
On the Amazon floodplain, the main predators of black caiman (Melanosuchus niger) 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 during 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. Careful 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 to be necessary to initiate attacks by any other species of predator. Results based on camera traps and vestiges differed, but use of vestiges was adequate for identifying the principal predators on eggs in black caiman nests and, in many circumstances, the vestiges may be better for estimating predation by humans. In this study, opening nests and handling eggs did not increase the number of attacks on black caiman nests.
Highlights
Susceptibility of reptile and bird nests to attacks by predators may vary with incubation phase and parental behavior [1,2]
We investigated the following questions: (1) Does the probability of egg predation on black caiman nests vary throughout the incubation period? (2) Does the proportion of time that females attend nests affect the probability of predation? (3) Does predation by one species of predator influence predation by other species? (4) Do the proportions of nests attacked by different predators estimated from records of vestiges reflect the proportions of nests effectively attacked by those predators? (5) Does opening nests and handling of eggs for research purposes make them more vulnerable to predation?
Predation was recorded in 32% of the 658 black caiman nests we monitored in Mamiraua Sustainable Development Reserve (MSDR)
Summary
Susceptibility of reptile and bird nests to attacks by predators may vary with incubation phase and parental behavior [1,2]. Black caiman nest predation (Melanosuchus niger) eggs are jaguars (Panthera onca), tegu lizards (Tupinambis teguixim), capuchin monkeys (Sapajus macrocephalus) and humans (Homo sapiens) [3,4]. It is not known if the intensity of attacks by predators varies throughout the incubation period or whether some nests are more vulnerable than others. Black caimans nest annually in the dry season (from September to January in Central Brazilian Amazonia) and the incubation period can extend up to 90 days [5,6]. Nests of black caiman are mostly located in flooded forests (varzea) around isolated water bodies where the water level rises later in the season [8]
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