Let’s start with the nest and the incubation period. One nest holds an average of 115 eggs. The eggs incubate between 55-60 days and loggerhead hatchlings emerge from January to March each year, in the southern hemisphere. The temperature of the surrounding sand determines the sex of the hatchling. Warmer (above 28 °C) means more females, cooler (below 28 °C) means more males. Rising temperatures, due to the climate emergency, could mean an imbalance in the sex ratio of turtle species.
Hatchlings emerge from the sand at night. Not only is it cooler, but they are also a little more protected from predators. They use the moon to guide them to the waters edge. Coastal developments, with artificial lighting, have become troublesome as they can cause the hatchlings to move in the wrong direction and become even more vulnerable.
There are still a variety of different predators waiting for these baby turtles and only one in 1000 hatchlings survives it into adulthood.
If a hatchlings makes it into the ocean, they begin a long solo journey out into the open ocean. Those born on the South African Kwa-Zulu Natal coast swim into the strong, and warm, Agulhas current. The current carries them, which means they can conserve energy and focus on growing. The downside of this life style is that many hatchlings can get carried too far down the coast and end up in the cold waters of our south coast. Due to hypothermia and general weakness, they sometimes get stranded on our beaches. The lucky ones are found by members of the public and brought to our turtle rehabilitation centre.
Not much is known about the life of a loggerhead turtle between being a hatchling and becoming a large sub-adult. If the turtle is strong and lucky enough to evade the multitude of predators they face, they enter what we call the ‘lost years’. For loggerheads, the lost years can last up to 12 years, where the turtle stays in the open ocean and focuses on growing bigger.
Once turtles are large enough, mostly to avoid being eaten by predators, they tend to move into warmer, tropical waters. These areas have more food, but are also more dangerous. This is why it is important for the turtle to be big enough to not get eaten.
Adult turtles occupy more shallow waters in this stage of their life and their main occupation is feeding. Once they have spent anything from one year to several years in this area, they migrate to common turtle breeding grounds.
Reproduction is hard work, especially for the females, so turtles only enter this stage of their life when they have fed enough to sustain them for a while. Sometimes the home feeding grounds of turtles are thousands of kilometres away from their breeding grounds.
Loggerhead turtles are only sexually mature at the age of 30. Mating takes place off-shore, after which the female turtle returns to her own birth beach. There she digs a hole and lays her eggs. Male turtles never return back to land and remain in the ocean until they die.
The breeding season of South African loggerhead turtles is between October and February each year. This coincides with the shift of the Agulhas current, which brings warmer waters closer to the shore. Once the female loggerhead has laid her eggs, she covers them up with sand and returns back to sea. Females may mate up to five times within one breeding season and return to lay her eggs each time.
Nesting sites along our coastline, and globally, are vulnerable and need to be protected.
We currently have just over 20 loggerhead hatchlings that hatched at the beginning of this year on our Kwa-Zulu Natal coast. We also have two large adult loggerhead turtles in our care, both of which will hopefully be released at the end of this year. If all of the hatchlings are healthy, they will also return to the ocean. You can read more about Annie, the female loggerhead turtle, here. We will do an update on Luis, the large male loggerhead turtle, next week.
If you would like to help and support our work with sea turtles, please consider making a donation. You can do so on our ‘Support us‘ page, or use our SnapScan QR code.
Claudine van Zyl completed her Work Imtegrated Learning (WIL) internship with us last year. Her research project was: ‘The characterisation of plastics in stranded post-hatchling loggerhead turtles along the South African coastline from 2015 to 2020’.
Bob, a green turtle in our care, has been with us since November 2014. While he is not ready for release yet, we are preparing him so that he has the best chance of survival back in the big blue. Alex Panagiotou, one of our turtle team specialists, is working with Bob through enrichment programmes and research.
Grant Blakeway completed the 2020 Talisker Whisky Atlantic Challenge by solo rowing 4 800 km across the Atlantic. He did this to highlight the issue of plastic pollution in the ocean.