High accuracy tracking reveals how small conservation areas can protect marine megafauna

Abstract

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 d 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% utilization 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 hundreds of kilometers from the tagging site. Our results show that, for some large marine vertebrates, even small protected areas of only a few square kilometers 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.

Satellite Tracking of Post-nesting Green Sea Turtles (Chelonia mydas) From Ras Baridi, Red Sea

“…However, the current designated protected areas alone will not provide protection for all members of the foraging aggregations because marine turtles display complex movements within and among large and/or disjunct foraging areas throughout the year (Hawkes et al, 2006;Shimada et al, 2016;Dujon et al, 2018). The designation of additional smaller protected areas that contain a range of habitats would benefit foraging turtles of different age/size classes as well as other marine species (Hays et al, 2021), particularly along the narrow coastal foraging areas located to the North and South of Jeddah. Because the destinations of the 16 post-nesting green turtles indicate that these turtles are using more areas than are currently within the designated management areas of the Red Sea, a review of existing and proposed management areas with a view to assess their effectiveness in protecting at-risk species and to provide habitat for multiple marine species is warranted (Rouphael et al, 2015;Gajdzik et al, 2021).…”

“…In combination with other methods (e.g., genetics), satellite tracking of marine turtles can be used to better define the uniqueness of nesting populations and shared use of habitat (Godley et al, 2010;Hart et al, 2012Hart et al, , 2020Bourjea et al, 2015;Jensen et al, 2019). In addition, satellite tracking of marine species has contributed to identifying important foraging areas (Pilcher et al, 2014;Stokes et al, 2015Stokes et al, , 2019, threatening processes (Hays et al, 2003;Hart et al, 2018), and helped with development of conservation and management options (Hays et al, 2014(Hays et al, , 2019(Hays et al, , 2021Pendoley et al, 2014;Hays and Hawkes, 2018).…”

Space‐use patterns of green turtles in industrial coastal foraging habitat: Challenges and opportunities for informing management with a large satellite tracking dataset

“…High fidelity and the tendency of green turtles to return to their foraging areas when displaced or following breeding migrations, may limit their resilience to local disturbances such as human development and extreme weather events (Shimada et al, 2016b; Shimada et al, 2020). In low density foraging areas where individuals of multiple age and size classes share habitat and show prominent residency, the protection of a few key sites at pertinent times is likely to confer considerable long‐term conservation benefits (Scott et al, 2012; Schofield et al, 2013; Hays et al, 2021). Identification of these sites and periods should consider habitat requirements for individuals at several life history stages and dynamic oceanographic and biological processes that characterize variations in resource availability including rainfall events, tidal flow regimes, senescence and reproduction of primary producers.…”

Confirmed feasibility of a satellite tracker attachment method on small juvenile hawksbill turtles Eretmochelys imbricata

“…The continued development of smaller trackers could eventually make the need for neoprene redundant; however, the likely size of a tag to fit one scute would be difficult to specify as the size and shape of scutes can vary greatly between individuals. Moreover, the 'bumpiness' of the individual scutes (Sal mon et al 2018) prevents a tracker from sitting well on just one scute alone; hence previous tracking studies have often targeted larger juveniles (Hays et al 2021) to which the tracker could be attached more easily. Sanding or scoring of the carapace is common during satellite tracker attachment (Balazs et al 1996), presumably to reduce the biofilm and increase surface area for better adhesion and longevity of tracker attachment (Hoffman 2020).…”