Failure to launch: what’s happening with Seychelles’ turtle and tortoise eggs?
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.
Alessia Lavigne
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...
Assessment of fertility and embryo survival rates for threatened turtle and tortoise species in Seychelles.
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:
- Examine unhatched eggs and collect data on egg fertility and embryo mortality rates for three threatened turtle and tortoise species (green and hawksbill turtles and Aldabra tortoise) across Inner and Outer Island populations, using cutting-edge methods recently tested for these taxa.
- Analyse differences in fertility and embryo mortality rates to identify the main drivers of hatching failure in Seychelles turtles and tortoises and how these vary between species and islands.
- Provide data, information and advice to conservation partners, based on the knowledge and data generated from the project, to help them increase the efficiency and success of conservation interventions aimed at the turtle and tortoise egg/nest phase.