Publicação

How high and low nesting season densities affect the patterns of nest site preferences and nest site fidelity of Caretta caretta, on Maio island, Cape Verde

Detalhes bibliográficos
Resumo:	When female sea turtles arrive to their natal regions to nest they encounter a heterogeneity of habitats. The choice of the place to lay the nest can affect enormously the survival and the future of the offspring. The assessment of female behaviour concerning nest placement and plasticity regarding this behaviour is important in the context of current climate change and has direct implications for selection of the nesting beaches to protect or manage. Maio island, in Cape Verde, is one of the main nesting islands of the archipelago for the loggerhead sea turtle, Caretta caretta, and it is known for its heterogeneity, with beaches of different sand colours (black, mixed and white) and lengths around the entire island. The subpopulation of loggerheads that nests there is classified as “Endangered” by the IUCN. Nevertheless, during the last years, the number of females arriving to the island appears to be increasing and, in 2018, the number of nests almost tripled, in comparison to 2017. This study aimed to compare the nest site distribution, amid these two contrasting years, and assess if the females with different body sizes select different nest sites. Overall, the results revealed that nests were not laid randomly across the island. Beach orientation was evidenced as the main variable influencing the selection of the nesting site in both nesting years, with the majority of individuals selecting beaches facing east and north east. This selection did not differ according to female body size. Regarding beach fidelity within the same nesting season, we found that individuals selected sites within a mean range of 8003 meters, in 2017, and 7035 meters, in 2018. The mean distance travelled per female between consecutive nesting events seemed to differ according to body size, since larger females tended to travel shorter distances than smaller females. Moreover, it was also tested if the hatching success varied among beach zones. Hatching success revealed to be similar between the vegetated and the mid-zone of the beach (42.5% and 41.3%, respectively). In the intertidal zone all nests were flooded by spring tide or lost to erosion. We also tested if each female showed fidelity regarding the nest placement along different beach zones and if they selected zones favourable to the development of embryos. An interesting result was that females tended to toggle between areas near the vegetation and in the open sand, avoiding the intertidal zone. Finally, the intensive monitoring effort allowed the identification of the most important beaches for loggerheads nesting each year on Maio island, as well as the identification of areas that will gain importance in a desirable future when “good” years will be the norm. Beaches facing east and north east of mixed and black sand colour received the highest number of nests in both years, while the areas amid Lagosteira - Pajoana; Casas Velhas -Djampadja; Praia do Morro - Salina Norte and Soca – Santana, , scattered around the island and not only on the east/ north east, were identified as potentially important areas. Jointly, these findings provide a more profound knowledge about the ecology of Caretta caretta and provide information that allow the implementation of more effective management plans.
Autores principais:	Oliveira, Ana Sofia Ribeiro de
Assunto:	Caretta caretta Áreas de conservação Ilha do Maio Fidelidade Distribuição dos ninhos Teses de mestrado - 2019
Ano:	2019
País:	Portugal
Tipo de documento:	dissertação de mestrado
Tipo de acesso:	acesso aberto
Instituição associada:	Universidade de Lisboa
Idioma:	inglês
Origem:	Repositório da Universidade de Lisboa