Identifying the drivers of reproductive failure in threatened turtles and tortoises

Turtles and tortoises are facing an extinction crisis, and ecosystems are at risk of collapsing with the loss of their crucial functions. Reproductive failure at the egg-stage represents a key barrier to population growth for many species, but little is known about the drivers of this failure, particularly in threatened wild populations.

Declining turtle and tortoise reproductive rates have been linked to human activity, both directly via the impacts of disturbance and pollution, and indirectly via global warming. Rising temperatures are causing female-biased sex ratios (due to temperature-specific sex determination), but the implications of this for sperm availability and fertilisation rates is unknown. Similarly, the influence of environmental factors, including anthropogenic activity, on hatching rates of fertilised eggs is poorly understood.

Using new methods for accurately distinguishing fertilisation failure from early embryo death in unhatched eggs, this project will combine data on (i) nesting attempts and hatching outcomes, (ii) climatic variables, and (iii) human activity, across multiple populations and locations in a multi-island system, to identify the key drivers of reproductive failure in threatened turtles and tortoises. The project will involve lab and fieldwork, collaboration with external conservation partner organisations, and computer-based work including data analysis using R.