Loading...
4 results
Search Results
Now showing 1 - 4 of 4
- Foraging behavior of juvenile loggerhead sea turtles in the open ocean: from Lévy exploration to area-restricted searchPublication . Freitas, C.; Caldeira, R.; Reis, J.; Dellinger, T.Most sea turtle species spend part of, or their entire juvenile stage in pelagic habitats. A key question is how pelagic turtles exploit their environment to optimize prey intake and max imize fitness. This study combined animal telemetry with remote-sensed environmental data to quantify the drivers and patterns of foraging behavior of juvenile loggerhead sea turtles in the pelagic eastern North Atlantic. Juveniles ranged in size from 34 to 58 cm straight carapace length. First-passage time (FPT) analysis, used to quantify search effort, indicated that turtles performed area-restricted searches at nested spatial scales of 10 and 50 to 200 km. High-usage areas, as quantified by FPT, were associated with increased dive activity and weak surface currents, as well as with oceanographic features (high chlorophyll a and shallower bathymetry) thought to stimu late prey availability. Conversely, low-usage areas (i.e. transit areas) were associated with deep, probably exploratory dives, typical from Lévy movement patterns. Further interpretation of dive data indicates greater dive activity in shallow depths (0 to 10 m) during the night and during tran sit. Conversely, greater activity at intermediate depths (10 to 50 m) was observed during daytime, under strong lunar illumination and in high-usage areas, suggesting these depths are major day time foraging layers. This study clarifies the foraging ecology of sea turtles during their develop ment phase in the open sea, providing evidence that these pelagic predators can adjust their for aging strategies and effort in response to the local conditions of their dynamic environment.
- Multidisciplinary oceanographic studies of a small island in the Southern California BightPublication . Caldeira, Rui Miguel Andrade; Hammer, William M.
- Surface behavior of pelagic juvenile loggerhead sea turtles in the eastern North AtlanticPublication . Freitas, Carla; Caldeira, Rui; Dellinger, ThomasSea turtles bask at the ocean surface, but little is known about the patterns and ecological context of surface behavior in the wild. This study investigated the surface behavior of ten juvenile loggerhead sea turtles (34 - 58 cm straight carapace length) satellite tagged in Madeira, in the pelagic eastern North Atlantic. During a total of 2273 tracking days, turtles moved through oceanic areas with a mean depth of ~3400 m. On average, turtles spent one third of the time at the surface (0 - 1 m depth), spending 43% of the time at the surface during the day and 29% of the time during the night. Generalized linear mixed modelling showed that the proportion of time at the surface was significantly larger during the day, particularly during spring and summer. Time spent at the surface during the day increased with elevated air temperatures and weak winds, probably to maximize the benefits of solar absorption. Conversely, the probability of being at the surface during the day decreased as horizontal search effort increased, suggesting a trade-off between basking and daytime foraging activities. At night, time spent at the surface was not associated with air temperature or wind speed but was instead positively associated with moon illumination. As turtles tend to dive deeper during clear nights, increased surface time may be needed to recover from deeper dives. This study presents important aspects of the behavioral ecology of the species during the oceanic juvenile phase. The findings reported here may be relevant for species management and conservation, including correction of census data and management of interactions with surface fishing gear and other anthropogenic activities.
- O papel do Observatório Oceânico da Madeira na promoção da literacia do oceanoPublication . Costa, Sónia; Caldeira, RuiA Literacia do Oceano é definida como a compreensão da influência que o oceano tem em nós e da nossa influência no oceano. Muitas instituições desenvolvem iniciativas nesta área. Na Região Autónoma da Madeira, o Observatório Oceânico da Madeira (OOM) tem atuado como facilitador e promotor deste tipo de literacia. Para isso, tem contado com o contributo de investigadores de várias áreas das ciências marinhas: Biodiversidade, Pescas e Maricultura, Modelação e Previsão Meteo-Oceanográfica, Teledeteção e Seguimento Remoto de animais marinhos. Entre 2016, ano em que iniciou ações educativas e de divulgação de ciência de forma regular, e 2019, o OOM contabilizou mais de 5500 alunos em cerca de 140 palestras, atividades teórico-práticas e lúdico-didáticas, foram ministrados 7 módulos formativos para professores e participou e organizou diversas iniciativas de aproximação da ciência ao público.