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Aspectos da migração, do nicho isotópico e do sucesso reprodutor da tartaruga verde no arquipélago dos Bijagós
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Abstract(s)
A tartaruga-verde é uma espécie ovípara que se distribui pelos oceanos e zonas costeiras tropicais, subtropicais e temperadas quentes, com grande capacidade migratória entre áreas de alimentação e reprodução. Esta espécie conta com uma dieta variada ao longo da sua vida, passando de carnívoras/omnívoras enquanto juvenis para maioritariamente herbívoras enquanto adultos. São espécies sem cuidados parentais, e as crias, após emergirem dos ninhos, fixam a assinatura geomagnética do lugar de origem, onde regressam para se reproduzir quando adultas. A tartaruga-verde é alvo de várias ameaças antropogénicas, ao longo da sua vida, sendo protegidas em vários países. O arquipélago dos Bijagós, Guiné-Bissau, alberga uma grande população nidificante de tartarugas-verdes, de importância mundial. Neste estudo pesquisaram-se o nicho trófico e as rotas migratórias após reprodução desta população, e determinou-se o seu sucesso reprodutor, taxa de predação e impacto da inundação sobre os ninhos. Através de análises dos isótopos estáveis e colocação de transmissores de GPS por satélite identificaram-se as áreas de alimentação desta população, nomeadamente os Bijagós, Senegal, Gâmbia e Mauritânia. As tartarugas-verdes dos Bijagós ocuparam uma posição mais alta na cadeia trófica e apresentaram um nicho trófico menos amplo, em relação às da Mauritânia. Na ilha de Meio verificou-se uma alta taxa de predação e de inundação dos ninhos, contribuindo para um baixo sucesso reprodutor, ao contrário da ilha de Poilão, onde o sucesso de eclosão foi alto.
The green turtle is an oviparous species that is distributed in throughout the tropical, subtropical and temperate warm oceans and coastal areas, with great a migratory capacity between feeding and reproduction areas. This species has a varied diet throughout its life, changing from carnivores/omnivores as juveniles to mostly herbivores as adults. They do not display parental care, and the hatchlings, after emerging from their nests, imprint the geomagnetic signature of their natal beach, where they return to reproduce as adults. The green turtle faces several anthropogenic threats throughout its life, being protected in several countries. The Bijagós archipelago, Guinea-Bissau, is home to a large breeding population of green turtles, of global importance. In this study, the trophic niche and the post-breeding migratory routes of this population were researched, and the reproductive success, predation and inundation rates on the nests were determined. Through the analysis of stable isotopes and the deployment of GPS satellite transmitters, the feeding areas of this population were identified, namely the Bijagós, Senegal, Gambia and Mauritania. The green turtles of the Bijagós occupied a higher position in the trophic chain and presented a less wide trophic niche, in relation to those of Mauritania. In the island of Meio there was a high rate of predation and flooding of the nests, contributing to a low reproductive success, unlike in the island of Poilão, where the hatching success was high.
The green turtle is an oviparous species that is distributed in throughout the tropical, subtropical and temperate warm oceans and coastal areas, with great a migratory capacity between feeding and reproduction areas. This species has a varied diet throughout its life, changing from carnivores/omnivores as juveniles to mostly herbivores as adults. They do not display parental care, and the hatchlings, after emerging from their nests, imprint the geomagnetic signature of their natal beach, where they return to reproduce as adults. The green turtle faces several anthropogenic threats throughout its life, being protected in several countries. The Bijagós archipelago, Guinea-Bissau, is home to a large breeding population of green turtles, of global importance. In this study, the trophic niche and the post-breeding migratory routes of this population were researched, and the reproductive success, predation and inundation rates on the nests were determined. Through the analysis of stable isotopes and the deployment of GPS satellite transmitters, the feeding areas of this population were identified, namely the Bijagós, Senegal, Gambia and Mauritania. The green turtles of the Bijagós occupied a higher position in the trophic chain and presented a less wide trophic niche, in relation to those of Mauritania. In the island of Meio there was a high rate of predation and flooding of the nests, contributing to a low reproductive success, unlike in the island of Poilão, where the hatching success was high.
Description
Dissertação de Mestrado apresentada no
ISPA – Instituto Universitário para obtenção de grau
de Mestre em Biologia Marinha e Conservação
Keywords
Migração Predação Tartaruga-verde Migration Predation Green turtle