Profile
I am a marine ecologist with long standing interests in the use of satellite tracking to examine marine animal movements and the impacts of climate change on marine systems. Working closely with Dr Nicole Esteban, my current work in the Chagos Archipelago includes assessment of the movements of both adult and juvenile green and hawksbill turtles. The long-term tracks show that for green turtles, females nesting on Diego Garcia may migrate to foraging sites across the Western Indian Ocean and travel indirect routes to these targets indicting migrating turtles only have a relatively crude map sense in the open ocean (https://doi.org/10.1016/j.cub.2020.05.086). Compared to post-nesting green turtles, hawksbill turtles travel much shorter distances to foraging sites on the Great Chagos Bank and other banks in the region, showing the broader ecological importance of these little studied habitats.
Our long-term records of sand temperature on nesting beaches in the Chagos Archipelago have revealed that shading of nests by vegetation helps to reduce incubation temperatures, helping to ensure both fairly balanced hatchling sex ratios as well as high egg survival (http://dx.doi.org/10.1038/srep20339). Further, we have shown that sea turtle nests across the archipelago are fairly resilient to the marine heatwaves that have devastated coral reefs in the region (https://doi.org/10.1098/rsbl.2021.0038). Long-term monitoring shows encouraging upward trends in the annual number of nests (https://doi.org/10.1017/S0030605319001108).
Among the topics we are exploring in ongoing work are the diet of turtles, foraging turtle densities using drone surveys, nest site selection and the vulnerability of nesting areas to sea level change.
In 1873, Charles Darwin marvelled at the ability of sea turtles to find isolated island breeding sites, but how turtles navigate remains perplexing. Our satellite tracking work has helped solve this riddle, showing turtles can reorient in the open ocean, but only at a crude level.
Biography
My Project
Other interests
I help to lead a collaborative global project (Megamove.org) to compare the patterns of movement across multiple taxa including sea turtles, sharks, marine mammals and birds including an assessment of the threats these animals face. Megamove has been endorsed by the UN Ocean Decade for Sustainable Development
My Publications
Nest Site Selection in Sea Turtles Shows Consistencies Across the Globe in the Face of Climate Change
Stokes, H.J., Esteban, N., Hays, G.C. (2024). Nest site selection in sea turtles shows consistencies across the globe in the face of climate change. Animal Behaviour.
A Pulse Check for Trends in Sea Turtle Numbers Across the Globe
Hays, G.C., Schofield, G., Papazekou, M., Chatzimentor, A., Katsanevakis, S., Mazaris, A.D. (2024). A pulse check for trends in sea turtle numbers across the globe. iScience.
Individual Variation in Home-Range Across an Ocean Basin and Links to Habitat Quality and Management
Hays, G.C., Rattray, A., Shimada, T., Esteban, N. (2024). Individual variation in home-range across an ocean basin and links to habitat quality and management. Journal of Applied Ecology.
Predation of Sea Turtle Eggs by Rats and Crabs
Stokes, H.J., Esteban, N., Hays, G.C. (2023). Predation of sea turtle eggs by rats and crabs. Marine Biology.
Synergistic Use of UAV Surveys, Satellite Tracking Data and Mark-Recapture to Estimate Abundance of Elusive Species
Stokes, H.J., Mortimer, J.A., Laloë, J.-O., Hays, G.C., Esteban, N. (2023). Synergistic use of UAV surveys, satellite tracking data and mark-recapture to estimate abundance of elusive species. Ecosphere.
