Study reveals Gabon is home to largest olive ridley turtle breeding colony in the Atlantic

Gabon has just added another feather to its cap of remarkable natural wonders - the largest breeding colony of vulnerable olive ridley turtles in the Atlantic.

A new study from the University of Exeter – based upon a huge ground survey covering nearly 600 km of Gabon’s coastline – has revealed that the Central African state could host up to 9,800 turtle nests per year compared with around 3,300 in French Guiana and 3,000 in Brazil.

Published in the journal Biological Conservation, the study is the first to combine existing monitoring data with a back-to-basics coastal survey of the area.
 
WWF Gabon played a key role in the project by providing over 12 seasons’ worth of nesting data from a 13 km-stretch of regularly monitored beaches in the Gamba Complex of Protected Areas. This information was used to ground-truth the data collected during October and November 2013 from the 600 km covered in the survey.
 
WWF Gabon also provided logistical support as well as manpower during the Gamba Complex portion of the survey.
 
“This study is exciting, because while we have always known how important Gabon is for leatherback turtles, olive ridleys were often overlooked,” said Dr Gianna Minton, WWF Gabon’s Marine Programme Coordinator. “Sadly, this is a species which seems to be the most heavily affected by accidental entanglement in fishing gear in the region. Knowing how important Gabon is for this species should motivate responsible parties to implement conservation measures at sea, as well as on land.”
 
Olive ridley turtles are one of the smallest of the marine turtles and are named for the greenish colour of their shell and skin. Although considered the most abundant of the marine turtles, there has been a net decline in the global numbers of the species, and they are currently listed as ‘vulnerable’ by the IUCN.
 
“Conservation efforts for sea turtles can be hampered by their migratory life cycles, which carry them across jurisdictional boundaries and international waters," said Dr Kristian Metcalfe, lead author from the Centre for Ecology and Conservation (CEC) at the University of Exeter, who undertook the coastal survey with colleagues. "That makes this first population assessment which covered extensive areas of Gabon’s coast outside of monitored regions all the more valuable and worthwhile, and demonstrates the importance of focusing beyond intensively monitored beaches.”

Olive ridley turtles nest on Gabon’s beaches between October and March, with a peak occurring in November.  Females come on to land three or four times during a nesting season to lay a clutch of 50-100 eggs, which then take roughly 60 days to hatch. The hatchlings make their own way to the sea, using the reflection of the stars or the sky on the water to guide them. 
 
Although a considerable proportion of nesting occurs within protected areas in Gabon, a range of illegal activities and external pressures highlight the need for continued conservation efforts.
 
“There have been increasing calls for improved sea turtle data at a local and regional scale to help inform conservation assessments," said co-author Professor Brendan Godley from the CEC. "Our study goes some way to providing the data needed and will help us understand sea turtle distribution, density, population trends and threats as well as allowing the people of Gabon to manage their marine resources more sustainably.”
 
The data generated as part of this study was used to inform the development of a new network of marine protected areas covering 23% of Gabon’s Exclusive Economic Zone, which was announced at the 2014 IUCN World Parks Congress.
 
WWF has been working in the Gamba Complex since 1991 and is a key member of the Gabon Marine Turtle Partnership, a unique collaboration between all of the NGOs, government agencies and academic institutions involved in marine turtle research and conservation in Gabon. 
 
In addition to the support from WWF and the Gabon Marine Turtle Partnership, the -study was funded by the Darwin Initiative through the British government, and received additional backing from WCS, Tullow Oil, and the Waitt Foundation.
 
WWF also played an important role in previous research, which established that Gabon hosts the most important nesting site in the world for leatherback turtles.