Caracterização do micro-habitat dos ninhos e predação dos ovos de Podocnemis erythrocephala em áreas de desova no Rio Ayuanã, AM

Abstract

Turtles of the Family Podocnemidae are an important source of protein for rural people in the Amazon Basin. The illegal commercial trade in turtles has reduced many populations of turtles to near extirpation locally. Podocnemis erythrocephala, restricted primarily to black water rivers, have been consumed by the rural communities for decades, and despite their relative abundance in the region of the Rio Negro, rural people are commenting about the decline of this species locally. The objective of this study is to collect information valuable for the future management and conservation of this species in Rio Negro Basin, in particular data concerning the reproductive ecology of this species in a tributary of the Rio Negro, the Rio Ayuanã. In the 2004 e 2005 nesting seasons a total of 93 and 174 nests were studied respectively. I collected morphological data of nests, eggs, and hatchlings. The areas of open Campina had the greatest abundance of nests. The sex ratio of the hatchlings was not different from 1:1. The distance from the nests to the forest was the only variable that characterized the microhabitat of the nests (0 to 20m from the forest edge). There was a positive correlation between the mass of the eggs and the number of eggs per nest. There was also a positive correlation between the hatching success and the length of incubation of the eggs. I observed that nests that were more widely dispersed, 20 to 25m between nests, had lower predation rates (45%) while those less dispersed, to 15m, had higher predation rates (70 to 80%). The open beach was the habitat with the lowest predation rate. The vegetation cover was the only factor that influenced the number of predated nests. Predators attacked 48.43% of the nests which had only olfactory cues. Whereas predators predated only 33.33% of the nests which offered only visual cues. Those nests which had both visual and olfactory cues were more heavily predated, 52%.