My name is Roisin McDonough, I'm 19 years old and live in the UK. I am currently studying Biological Science at the University of Bristol. My interests in conservation led me to take part in a 4 week conservation project with Wildlife Sense as an intern. It has been an unforgettable experience, and I have loved every minute of it. I have gained hands on experience with the methodologies used to protect sea turtle nests and learnt how to create beach profiles, that monitor the changes the beaches go through. As I have only just finished my first year at University I did not have an assigned project in which I collected data, instead, I came with a question and throughout my time Chanel and Nikos provided me with answers; through readings of various literature and 1 on 1 meetings.
My interests were the causes of mortality at each stage of a sea turtles life. By knowing the primary causes of mortality it gives a better understanding of the procedures needed to protect this endangered species. With regards to the eggs, although fertility is typically greater than 80%, occasionally abnormal eggs are produced; yolkless, multi-yolked, chain-form and shell-less eggs. I had the chance to see chain-form eggs within a nest for myself. These eggs were then removed from the egg chamber and moved to a new site, so to give the normal eggs a better chance of emerging successfully. The nesting environment, including, moisture, gas exchange, sand temperature and inundation are the main factors related to either the success or mortality of the eggs. It was interesting to find that if inundation occurs near the end of incubation, the entire clutch may die, due to the higher demand of oxygen needed, compared with the earlier developmental stages. With hatchlings, the emergence success is generally lower than hatching success, as some of the hatchlings that break free from their eggshells may die whilst still in the chamber. However, hatching and emergence success is also generally high; over 80%.
One of the main causes of mortality at this stage is depredation, by terrestrial or aquatic predators. By emerging at night the risk is lowered, darkness being there protective factor. Also, the sand temperature will be sub-lethal at night. By following the light of the moon the hatchlings find there way to the sea shore, this is why bar lights on beaches can affect the mortality of hatchlings by causing them to become disorientated and thus travel inland, where they may die of dehydration, predation etc.
During the juvenile and adult life stages there are many different types of threats that can affect their survival. These threats are specifically related to the habitat in which the sea turtle is living in. Juveniles spend the majority of their time in the oceanic zone; where depths are greater than 200m. Large juveniles and adults also exploit the neritic zone; the nearshore marine environment, where depths do not exceed 200m. Threats faced in the neritic zone are marine debris. Thousands of sea turtles ingest plastics, mistaking them for food. Most of the debris is visible and can be removed if possible, such as, plastic bags, food wrappers, bottles etc., however, some plastics are invisible to the naked eye and if these particles are ingested the turtle can become sick and even starve. Threats related to the oceanic zone are primarily to do with commercial fishing. Sea turtles can be accidentally captured in fisheries, either by highly mechanised systems, or by small scale fishermen. Sea turtles may also be injured or killed by longlines, or drowned in gill nets. Vessel strikes can also be detrimental to sea turtles; occasionally turtles were spotted with such strikes on harbour shifts.