Green turtle population recovery at Aldabra continues after 50 years of protection |12 March 2022
An early morning nesting green turtle on Settlement Beach on Aldabra Atoll (Photo: © Richard Baxter)
The Aldabra Atoll has the second largest green turtle population in the region, which is still growing, thanks to 50 years of enforced protection.
A new paper published recently in the journal Endangered Species Research by a team of researchers from the University of Exeter and the Seychelles Islands Foundation, confirms the continued increase of green turtles Chelonia mydas at Aldabra.
The paper, lead-authored by University of Exeter MSc graduate Adam Pritchard, and co-authored by several SIF current and former staff, estimated turtle egg clutches over 50 years of protection and monitoring, and shows an increase in clutches of 410–665% since 1968.
Considered Endangered by the IUCN, green turtles have suffered massive historical population declines due to intensive harvesting of nesting females. Aldabra Atoll was the first green turtle nesting site to be protected in the Western Indian Ocean, with a ban on turtle capture in 1968. Aldabra’s turtle monitoring programme started the same year, making it the region’s longest-running turtle track data collection programme.
Data collected from more than 44,000 turtle track surveys across Aldabra’s six beach groups in a 40-year period from 1980 to 2019 was analysed for the paper, with historic estimates from the 1960s used to determine the full extent of the turtles' recovery. The results, from over 128,000 turtle tracks, revealed that green turtle clutches have increased at Aldabra by 2.6% per year overall, with the greatest increase at Settlement Beach on Picard, where exploitation of nesting females was historically the most intense.
The paper estimates a seasonal nesting average of 3059–5099 female turtles nesting at Aldabra. Co-author, Cheryl Sanchez, who is currently doing a PhD on Aldabra’s turtles says, “This study demonstrates the importance of long-term monitoring, which is often seen as less glamorous and valuable than targeted research. It has taken decades of tireless commitment to collect the data to confirm this increase, and the foresight to protect the nesting population before it was too late. Aldabra’s green turtles should continue to be an incredible conservation success story that we can follow for decades to come.”
The paper is the outcome of a desk-based MSc study by Adam Pritchard, and an example of SIF’s approach to enlisting MSc project students to address key research questions, particularly data analysis gaps which cannot be filled on site. Adam says, “It's been an honour to record the continuous population increase of Aldabra's green turtles and help deliver a much-needed ‘good news’ conservation message which will hopefully encourage similar programmes. It just goes to show that, given the opportunity, animals have an astonishing capacity to recover from exploitation”.
These numbers confirm Aldabra, the longest continually protected and monitored nesting green turtle site in the Western Indian Ocean, as the second largest monitored green turtle rookery in the region. The research also shows the considerable contribution of Aldabra to regional green turtle numbers and clearly demonstrates the benefits of long-term protection and monitoring. Furthermore, with Aldabra’s turtle population still being well below estimated pre-exploitation population numbers, the increase is likely to continue.
This substantial increase in nesting turtles is a national conservation success and one that should make all Seychellois proud, considering the long-term country-wide commitment to the protection and monitoring of this iconic site.
Additional recommendations and avenues for further research can be found in the paper which is open access and can be accessed here: https://www.int-res.com/abstracts/esr/v47/p205-215/
Full paper reference:
Pritchard AM, Sanchez CL, Bunbury N, Burt A, Currie J, Doak N, Fleischer-Dogley F, Metcalfe K, Mortimer J, Richards H, van de Crommenacker J, & Godley B. (2022). Green turtle population recovery at Aldabra Atoll continues after 50 years of protection. Endangered Species Research 47: 205–215. doi.org/10.3354/esr01174
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