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.
Sentinel Species ResearchThe Ecology of Sea Turtles in the Indian Ocean Region
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
Travel routes to remote ocean targets reveal the map sense resolution for a marine migrant
Hays, G.C., Atchison-Balmond, N., Cerritelli, G., Laloë, J.O., Luschi, P., Mortimer, J.A., Rattray, A., and Esteban, N., (2022) Travel routes to remote ocean targets reveal the map sense resolution for a marine migrant. Journal of the Royal Society Interface
A Global Review of Green Turtle Diet: Sea Surface Temperature as a Potential Driver of Omnivory Levels
Esteban, N., Mortimer, J.A., Stokes, H.J. et al. A global review of green turtle diet: sea surface temperature as a potential driver of omnivory levels. Mar Biol 167, 183 (2020). https://doi.org/10.1007/s00227-020-03786-8
Open Ocean Reorientation and Challenges of Island Finding by Sea Turtles During Long-Distance Migration
Hays, G.C., Cerritelli, G., Esteban, N., Rattary, A. and Luschi, P. (2020) Open ocean reorientation and challenges of island finding by sea turtles during long-distance migration. Current Biology.
A Review of a Decade of Lessons From One of the World’s Largest MPAs: Conservation Gains and Key Challenges
Hays, G.C., Koldewey, H.J., Andrzejaczek, S., Attrill, M.J., Barley, S., Bayley, D.T.I., Benkwitt, C.E., Block, B., Schallert, R.J., Carlisle, A., Carr, P., Chapple, T.K., Collins, C., Diaz, C., Dunn, N., Dunbar, R.B., Eager, D.S., Engel, J., Embling, C.B., Esteban, N., Ferretti, F., Foster, N.L., Freeman, R., Gollock, M., Graham, N.A.J., Harris, J.L., Head, C.E.I, Hosegood, P., Howell, K.L., Hussey, N.E., Jacoby, D.M.P., Jones, R., Pilly, J.S., Lange, I.D., Letessier, T.B., Levy, E., Lindhart, M., McDevitt-Irwin, J.M., Meekan, M., Meeuwig, J.J., Micheli, F., Mogg, A., Mortimer, J.A., Mucciarone, D.A., Nicoll, M.A., Nuno, A., Perry, C., Preston, S.G., Rattray, A.J., Robinson, E., Roche, R., Schiele, M., Sheehan, E.V., Sheppard, A., Sheppard, C., Smith, A.L., Soule, B., Spalding, M., Stevens, G.M.W., Steyaert, M., Stiffel, S., Taylor, B.M., Tickler, D., Trevail, A.M., Trueba, P., Turner, J., Votier, S., Wilson, B., Williams, G., Williamson, B., Williamson, M.J., Wood, H. and Curnick, D.J. (2020) A review of a decade of lessons from one of the world’s largest MPAs: conservation gains and key challenges. Marine Biology.
Addressing Tagging Location Bias to Assess Space Use by Marine Animals
Hays, G.C., Rattray, A. and Esteban, N. (2020) Addressing tagging location bias to assess space use by marine animals. Journal of Applied Ecology.