“They look prehistoric!” The startled observers of sea turtles on the beaches of French Guiana are closer to the truth than they realise. The first forms of sea turtle appeared during the Lower Cretaceous over 120 million years ago. And the anatomy of certain fossils that have been found suggests that they looked like the turtles which are around today. Isn’t there something fascinating in imagining that the ancestors of these marine reptiles could have lived alongside the dinosaurs? And that unlike the dinosaurs, certain species managed to survive the great extinction crisis 65 million years ago which wiped out a considerable number of living organisms from the surface of the planet. Sea turtles have managed to adapt to the major changes in climate and geomorphology that have affected the Earth through the ages, to colonise the oceans, and so arrive in our present day when finally, due to human folly, they are threatened with extinction. The overexploitation of marine resources, the urbanisation of sites where they lay their eggs, the pollution of the oceans, poaching, etc, mean that sea turtle populations are gradually declining and may eventually die out.

Today there are seven species all belonging to the order of chelonians, divided into two families: the Cheloniidae and the Dermochelyidae. The latter family only has one species, the leatherback sea turtle (Dermochelys coriacea). As its name indicates this turtle has leathery skin on its back (from the Greek dermo meaning skin and the Latin corium meaning leather). Unlike the six other species of Cheloniidae it is not covered in scales.

French Guiana – a hotspot

What does French Guiana have to do with all this? Thousands of female green, leatherback, and olive ridley sea turtles have chosen the sandbars along the Guiana Shield to come and make their nests and lay hundreds of thousands of eggs, a process which is obviously essential for the survival of the species. When it comes to conserving sea turtles, French Guiana is clearly a priority area.

When in the late 1960s the beaches in Western French Guiana were recognised as sites of global importance for egg-laying by leatherbacks, a vast study programme of these animals was set up. Over the course of the following decade a team from the French National Museum of Natural History, with the support of the WWF and the French Ministry of the Environment, started counting the nests and identifying the female leatherbacks on all the beaches in Basse-Mana, which now form the Amana Major Reserve. With sometimes as many as 1000 sea turtles observed in one night, the region’s importance for the species was confirmed and resulted in one of the largest conservation projects ever seen in French Guiana, the Kawana campaigns. Seasonal campaigns on Yalimapo and secluded beaches carried out with the involvement of the Kalina community of Awala-Yalimapo and drawing on the support of hundreds of volunteers resulted in a real dynamic around the leatherback, and emblematic figure of French Guiana, which aroused the interest of the media, tourists, and by a ricochet effect, of partners.

New laying sites around Cayenne

At the time of the first campaigns, the scientific community was far from imagining that a few decades later an even more important phenomenon would be occurring on the other side of the territory. In the past, the presence of sea turtles in the East was frequently observed, but never in large numbers. In the late 1990s the thickening of the sandbars and the observation of turtles laying eggs right next to houses aroused the curiosity of members of Kwata (an association in French Guiana for nature protection). After having spent several nights exploring the beaches of Cayenne and Montjoly it became clear that leatherbacks were once again laying around the capital and, what was even better, olive ridleys were also observed nesting there. Historically, olive ridleys were known to lay their eggs in Suriname and French Guiana, but species numbers had been falling alarmingly since the late 1970s.

With the support of the French Ministry of the Environment, the WWF, the Space Centre, and the municipality of Rémire-Montjoly, this important information enabled the association to set up a sea turtle conservation programme in eastern French Guyana in the early 2000s. Nowadays it is based on several aspects involving dozens of volunteers who are passionate about the issue and help out every year. Females and their egg-laying are monitored by tagging the animals with a chip (PIT tagging) and by counting the nests every day. A major information campaign on the beaches and in the schools has also been put in place, accompanied by information documents for the general public. Lastly, teams carry out rescue operations for animals in difficulty, most of the time with the help of the Fire Brigade, especially when it requires freeing a turtle trapped in a net.

The figures speak for themselves when it comes to evaluating the importance of the beaches on the island of Cayenne for turtle nesting. Between 1998 and 2003 the number of leatherback turtle nests rose from 1000 to nearly 6,400, and from 500 to 2,600 for olive ridleys. How can we explain the scale of recent turtle activity in this area? It is a complex issue, since many parameters come into play and, especially, what has been observed over the past ten years is fundamentally different for the two species. In fact it is two distinct phenomena.

High stakes for Olive Ridleys

Despite the increase in occurrences of egg-laying, recent studies of the olive ridley sea turtle tend to show that the status of the species in French Guiana is still cause for concern. It would appear to be a relic population, probably descended from the French Guiana and Suriname populations in the middle of the last century which have now virtually disappeared. With 2500 occurrences of laying per year, the beaches of the island of Cayenne are currently home to nearly 75% of females in the region, making it one of the main breeding sites for the species in South America. Clearly, the stakes are high for these few kilometres of urbanised beach where the sea turtles need to overcome numerous threats. Sea turtles have evolved over time and developed a breeding strategy based on sheer weight of numbers to overcome the numerous natural mortality factors (predators, erosion, etc). Thus out of the thousands of eggs deposited by a female over the course of her life, very few will result in a breeding adults. The increasing number of threats from man is currently endangering this strategy of numbers. The imbalance is real, and the populations are heading towards extinction. For a long time now the Kwata association has closely monitored the activity of this the smallest of the sea turtles. Between 2006 and 2008 the multi-partner CARET program (Coordinated Approach to Restore our Endangered Turtles), led by the WWF and financed by the EU INTERREG funding initiative, generated new data about the species in the Guianas.

Modern study instruments

As part of this programme the Kwata Association has carried out a study into the genetics of the olive ridley so as to better understand the population structure and assess its fragility by analysing the degree of genetic diversity observed.

Initial results indicate that these sea turtles form an isolated population specific to French Guiana, apparently with little or no exchange with populations of neighbouring countries. The other piece of information is that the olive ridleys in French Guiana have a very low degree of genetic diversity, indicating that the pressures weighing down on breeding turtles for decades now have seriously weakened the health of the population.

In the light of these results it is clear how important the stakes are on the beaches in the East for the survival of the species in the region. The isolation and fragile state of the population mean that it will take many generations for it to recover sustainably.

In parallel, a team from the Strasbourg CNRS carried out a study into the marine behaviour of the olive ridleys. About twenty turtles were fitted with Argos® tags and monitored, generating precious information about the animals’ movements. The results of this sort of study provide precious input for setting up appropriate conservation measures. It makes it possible to target the zones where they interact with human activity, and can reveal if a species moves from one country to the next. For the specific case of the olive ridleys tagged in French Guiana, conservation efforts need to operate internationally and regional cooperation will be required to save this small population because, once they have laid their eggs, the tagged females headed off to Suriname and Guyana, where they looked for food in the estuaries of the major rivers.

The arrival of a population of leatherback sea turtles

For the leatherback turtle we are not witnessing a relic population but apparently the arrival of some of the Atlantic population at the laying sites on the island of Cayenne. The species appears to function by “population islands” that come to accessible beaches when conditions are favourable for varying periods of time. This could well be the case for the beaches of Montjoly and Cayenne which, having long been mangrove zones have once again become sandbars available for laying eggs. A genetic study of the leatherbacks in French Guiana is being carried out to better understand their population dynamics and try to pierce certain mysteries which puzzle a certain number of those involved in the conservation of sea turtles.

An effect of climate change

In addition to the increased length of beach which has become available over recent decades, other hypotheses have been put forward to explain why there are more turtles laying eggs, something which is not specific to eastern French Guiana. In several regions of the Caribbean more leatherbacks are being spotted. Taken with all the necessary precautions, some suggest that this is a consequence of current climate change. Alterations in the sea currents, increased water temperature and the proliferation of jellyfish (the main food source for leatherbacks) are all factors which could help populations of leatherback sea turtles.

There is also another hypothesis which ought not to be neglected and which could explain the increased level of egg-laying. Maybe the conservation measures undertaken over the past twenty years are beginning to have an effect? International initiatives to reduce interaction with fisheries, in conjunction with the work of NGOs on the beaches and the development of regulatory mechanisms by States might well be starting to bear fruit. When taken in conjunction with the hypotheses detailed above, we can perhaps fancy that all these efforts are not in vain. The thousands of eggs laid encourage us to continue our efforts so that the decline in sea turtle numbers, which has already lasted too long, can be reversed.