For dwindling numbers of tortoises and turtles, ensuring that your eggs hatch successfully to launch the next generation is key to population stability or recovery. But for threatened species of hawksbill and green sea turtles and the land-based Aldabra tortoise in Seychelles, eggs that don’t hatch with no clear explanation could spell disaster. Alessia is investigating the causes of hatching failures for these species with a view to identifying the key elements that require conservation and management intervention. With the right information, policies to protect these species can be more specific and successful.
Born and raised in Seychelles, I might have taken for granted its lush vegetation, stunning biodiversity and beautiful beaches. I am grateful I didn’t. From exploring Justin Gerlach’s tortoise and terrapin sanctuary during my early childhood on Silhouette to my participation in the D’Arros Experience programme and first job working with sea turtles, my constant affinity for nature, and turtles in particular, shaped my path to pursue a degree in zoology.
I strongly believe that to preserve the world’s biodiversity efficiently, we need to work together to bridge the gap between science and conservation. For me...
The aims of this project are to improve our understanding of the causes of hatching failure in threatened Seychelles turtle and tortoise populations and to provide important information about population fertility rates that will inform management interventions by Seychelles’ conservation organisations.
The failure of eggs to hatch is a major barrier to the recovery of threatened turtle and tortoise populations. Many unhatched eggs may show no signs of development, but it is unknown whether they fail due to fertility issues (problems with sperm or egg function) or the death of the embryo. This distinction is crucial for understanding the potential environmental and human-mediated drivers of infertility and embryo death and devising effective conservation interventions to improve hatching rates.
Turtles and tortoises are facing an extinction crisis, and ecosystems around the world will be at risk of collapsing when they lose the crucial services the reptiles provide. In Seychelles, sea-grass meadows – with their huge potential to sequester carbon dioxide – depend on the grazing of green turtles to stay healthy. Without them, the meadows become overgrown, obstructing currents and promoting the growth of detrimental slime moulds and algae. Similarly, hawksbill turtles play an important role in controlling the growth of marine sponges that aggressively compete with reef-building corals, which are already struggling to recover from devastating bleaching events. On land, Aldabra tortoises shape the habitats of Seychelles islands by grazing on plants, dispersing seeds and trampling areas of vegetation, all of which bring vital benefits for the wider ecosystem. Given their importance for the flora and fauna of Seychelles, it is vital that populations of turtles and tortoises are conserved.
A key barrier to population growth in turtles and tortoises is the failure of eggs to hatch. Hatching rates are a useful indicator of the reproductive health of a population, but unhatched eggs that show no signs of development are often ignored or assumed to be unfertilised. This is a problem, because undeveloped eggs often contain embryos that died at an early stage of development. Misclassifying these eggs can lead to infertility rates being overestimated and erroneously linked to environmental factors. Accurate differentiation of fertilisation failure from embryo mortality in undeveloped eggs would allow the reproductive health of a population to be monitored precisely; a better understanding of the potential drivers of infertility versus embryo death to be gained; and fertility rates for individuals and populations to be reliably estimated. In turn, these outcomes would inform conservation management strategies aimed at improving breeding success in threatened species.
To achieve our objective of improving our understanding of the causes of hatching failure in threatened Seychelles turtles and tortoise populations, we will:
Outside the USA, The Bahamas is the only place where Critically Endangered smalltooth sawfish can reliably be found. Tristan wants to ensure that protection measures in The Bahamas are understood and enforced as far as sawfish are concerned to close the current gap between policy and the people. He’ll be using aerial surveys, sonar and BRUVs, combined with interviews that draw on local knowledge, to identify essential sawfish habitats that need protection. Engaging with the community through workshops and by training students and meeting with government, Tristan intends to advocate for smalltooth sawfish protection throughout The Bahamas’ territorial waters.
Steven and Kevin are using genetic techniques to understand how Caribbean reef shark populations are connected across the extent of their range. Populations of this Endangered shark are in decline generally, but where they are managed and there is effective protection, their numbers are stable. With the integration of the correct information, Steven and Kevin are convinced that we can give Caribbean reef sharks a better shot at recovery and population stabilisation. They will also explore any barriers to connectivity, looking to the future recruitment and recovery of these sharks.
With very little information available about Endangered sicklefin devil rays, their seasonal aggregations at sea mounts in the Azores give Sophie an opportunity to learn more about their lives. She will be collecting satellite-tracking data that show how they move in the Azores’ exclusive economic zone. The information she collects will be used to develop maps of how the rays are using the zone and to identify essential areas that multiple species use. With this information at hand, Sophie hopes her work can contribute to a network of marine protected areas.