Taxon:
Chelonia mydas

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Scientific Name
Chelonia mydas
Common Name
Green Sea Turtle
common green sea turtle
Taxa Group
Cheloniidae
Environment
Move Mode

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Author: Rattray, Alex ×

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    Data from: High accuracy tracking reveals how small conservation areas can protect marine megafauna
    (2021-07-21) Hays, Graeme C.; Mortimer, Jeanne A.; Rattray, Alex; Shimada, Takahiro; Esteban, Nicole
    Space use estimates can inform conservation management but relaying high-accuracy locations is often not straightforward. We used Fastloc-GPS Argos satellite tags with the innovation of additional data relay via a ground station (termed a “Mote”) to record high volumes (typically > 20 locations per individual per day) of high accuracy tracking data. Tags were attached in the Chagos Archipelago (Indian Ocean) in 2018-2019 to 23 immature turtles of two species for which there have been long-standing conservation concerns: 21 hawksbill turtles (Eretmochelys imbricata) and two green turtles (Chelonia mydas). Over long tracking durations (mean 227.6 days per individual), most turtles moved very little. For example, 17 of 21 hawksbill turtles remained continuously in the lagoon where they were equipped, with 95% and 50% Utilisation Distributions (UDs) averaging only 1.03 and 0.18 km2 respectively. Many individuals, and both species, could use the same small spaces, i.e., individuals did not maintain unique home ranges. However, three hawksbill turtles travelled 100s of km from the tagging site. Our results show that for some large marine vertebrates, even small protected areas of only a few km2 can encompass the movements of a large proportion of individuals over long periods. High accuracy tracking may likewise reveal the details of space use for many other animals that move little and/or use important focal areas and where previous low-accuracy tracking techniques have tended to overestimate space use.
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    Data package
    Data from: Study "Green turtles (Chelonia Mydas); Hays; Chagos Archipelago, Western Indian Ocean"
    (2024-01-23) Hays, Graeme C.; Esteban, Nicole; Rattray, Alex
    Estimating the absolute number of individuals in populations and their fecundity is central to understanding the ecosystem role of species and their population dynamics as well as allowing informed conservation management for endangered species. Estimates of abundance and fecundity are often difficult to obtain for rare or cryptic species. Yet, in addition, here we show for a charismatic group, sea turtles, that are neither cryptic nor rare and whose nesting is easy to observe, that the traditional approach of direct observations of nesting has likely led to a gross overestimation of the number of individuals in populations and underestimation of their fecundity. We use high-resolution GPS satellite tags to track female green turtles throughout their nesting season in the Chagos Archipelago (Indian Ocean) and assess when and where they nested. For individual turtles, nest locations were often spread over several tens of kilometres of coastline. Assessed by satellite observations, a mean of 6.0 clutches (range 2–9, s.d. = 2.2) was laid by individuals, about twice as many as previously assumed, a finding also reported in other species and ocean basins. Taken together, these findings suggest that the actual number of nesting turtles may be almost 50% less than previously assumed.