Who I amAfter completing a degree in nature conservation in Pretoria, South Africa, I spent the first part of my career in the African bushveld, where I studied the movements of white rhinos, conducted anti-poaching patrols and guided on safaris. Several years later I took a temporary job as a botanical guide at Rocktail Bay on the northern coast of South Africa. During my first encounter with a nesting turtle on the beach, I was so inspired by these vulnerable creatures that I sensed a major fork in my career path. Soon I became hopelessly addicted to the ocean and spent all my spare time getting to know it.
After hastily completing my honours degree, I returned to Rocktail as a turtle researcher and stayed there for nearly two years. My persistent hunger for adventure eventually won me a four-month voluntary position at Aldabra, a remote, untouched coral atoll teeming with turtles and other marine life. I loved it so much out there that I ended up staying for five years, working as the chief scientific officer.
In 2006 I was offered an opportunity to conduct my PhD on the foraging ecology of the Critically Endangered hawksbill turtle at D’Arros Island and St Joseph Atoll in the Amirantes, a group of islands and atolls in the Seychelles. I spent the next five years following turtles around underwater and gaining an intimate understanding of the area and its surroundings. In 2011 I completed my PhD and took up the position of scientific director of the D’Arros Research Centre.
Where I workThe natural environment of D’Arros Island and St Joseph Atoll is among the most pristine and spectacular in the world. Scores of sharks, manta rays, turtles, stingrays and fishes inhabit the lagoon and the surrounding coral reefs, while flocks of seabirds roost in trees overlooking tranquil beaches. The D’Arros Research Centre, where we are based, is situated on the beach crest of D’Arros Island and overlooks the ocean. We often spot turtles, mantas, sharks and dolphins from our office! Just this morning, while we were preparing some research equipment, a hawksbill turtle emerged from the sea and nested right in front of the centre. As we watched it, a train of several manta rays passed by just 50 metres out to sea.
Although it’s the largest of the 17 islands that comprise the D’Arros and St Joseph chain, D’Arros is small enough that you can walk along its uninterrupted sandy beach and complete a circuit of the entire island in just two hours. About 30 people live here to maintain the infrastructure and conduct research, but all the remaining islands are uninhabited.
Daily activities from the centre are diverse and include regular scuba diving to monitor the coral reefs and download remote sensors, travelling on the boat to collect ID photos of manta rays and walking the beaches to tag turtles. We usually have several researchers, students and volunteers working on various projects and thus we enjoy a productive and pleasant atmosphere on the island.
What I doHawksbills are gentle, charismatic creatures whose global population has been decimated by more than 80% over the past century due to the demand for their shells (tortoiseshell actually comes from hawksbills). These Critically Endangered turtles spend most of their long adult lives at a particular foraging ground, where they maintain small home ranges and feed mostly on sponges. Every few years, however, females undertake epic oceanic migrations to nest on the same beaches that they themselves emerged from as hatchlings.
D’Arros and St Joseph are among the few places where the nesting population appears to be increasing because the private owners have protected the turtles since 1975. Indeed, ours is currently one of the biggest hawksbill rookeries in the Western Indian Ocean. Although significant resources have been allocated to protecting and studying these turtles while they nest at D’Arros and St Joseph, very little is known about their conservation status at the foraging grounds where they spend 85–95% of their adult lives. The reason is simple: the location of these habitats is still a mystery.
At present, satellite telemetry offers the only means to follow the long-distance movements of sea turtles. The tracking of post-nesting hawksbills from beaches of the granitic islands of the Seychelles Bank has shown that, in most cases, the turtles migrated to offshore sites within the confines of the same bank, less than 175 kilometres away. One turtle, however, migrated to Madagascar, covering a distance of 1,188 kilometres. The Amirantes Bank lies 200 kilometres south-west of the Seychelles Bank and is both smaller and more isolated. So, do female hawksbills nesting in the Amirantes show a similar tendency to use foraging grounds within Seychelles territory, perhaps even within the confines of the Amirantes Bank, or do they migrate further afield, perhaps as far as Madagascar (830 kilometres) or even the African mainland (1,500 kilometres)?
Information about the location of foraging grounds and the routes taken to reach them is vital for the effective protection of the species. At some foraging grounds the turtles may be the target of fisheries or be captured as by-catch in fishing gear, or they may face threats related to shipping, pollution or seismic exploration and petroleum mining. By tracking seven post-nesting females from D’Arros and St Joseph by satellite, we should learn much more about the life history of this Critically Endangered species and enhance its regional conservation status.
In the Seychelles, the hawksbill nesting season peaks between October and January, so we deployed the transmitters in January 2014 just before the females began their post-nesting migration. Although there were fewer nesting turtles around so late in the season, we managed to deploy all seven transmitters in eight days (15–22 January). To find these turtles, we circumnavigated the D’Arros beach roughly four times per day. Once we had located a turtle, we waited for her to finish nesting and then confined her inside a mobile wooden enclosure. We cleaned and prepared her carapace, then carefully glued a SPOT5 satellite tag (Wildlife Computers) to her back. After a minimum drying period of three hours, we released the turtle.
All seven turtles migrated to foraging grounds on the Seychelles Bank, 200 kilometres north-east of D’Arros and St Joseph. This is an encouraging result for hawksbill conservation because most of the sizable D’Arros and St Joseph nesting population appears to remain within the comparatively protected waters of the Seychelles. The government and local NGOs have invested generously in the protection of turtles and their habitats, and the nation’s territorial waters can be considered one of the safest for turtles in the Western Indian Ocean (especially on the Seychelles Bank, where foreign vessels are not permitted to fish). It is reassuring to know that the majority of these turtles do not migrate to other countries, where they are likely to find less protection, and that they do not undertake lengthy open-ocean migrations through a treacherous latticework of long-lines and trawl nets.
In terms of their detailed movements, the straight-line distance from D’Arros to the foraging grounds ranged between 135 and 366 kilometres and it took the turtles between 33 and 80 days to reach their destinations. Interestingly, it appears that two turtles lost their way and travelled 1,416 and 1,156 kilometres respectively!