Every summer in the southern hemisphere, islands of the tropics and countries bordered by water experience turtle season. This is when female turtles leave the safety of the water to attempt to lay their eggs. Turtles have been doing so for millions of years and it is quite extraordinary that these water dwelling reptiles use this specialised system in order to ensure the survival of their species. In last week’s ocean story, I wrote about the female turtles of Cousine Island in the Seychelles.
Cousine is a small granitic island in the middle of the Indian Ocean, 4 degrees south of the equator. It is an important breeding habitat for the critically endangered Hawksbill turtle and also one of few sites where they breed during the day. On this island, we would begin our turtle walks at 6am and undertake our last at 6pm. Walking up and down a stretch of beach on a tropical island may seem idyllic, and it is, but it is also harder work than one might imagine.
One of the objectives of these walks is to try to ensure we don’t miss a turtle laying. Missing nests is unfortunately an inevitability, but doing so can cost you three hours of your day as you dig around the nesting site in order to locate the eggs. On Cousine Island, we would mark every nest with a GPS and a set of poles to ensure we could monitor it and fence it at the 50-day mark. If the eggs have been laid in an area below the highwater mark, or one known for erosion or a high ghost crab density, we had to move the nest.
Moving nests is ideally done as soon as the female lays. Eggs are caught, counted and then placed carefully in a bucket with a layer of sand at the bottom. When they first come out, these eggs feel like ping-pong balls and are fairly flexible, which makes sense given that they drop 20–30cm down into the hole mother turtle has dug.
As the eggs age, they get harder and so it is not advisable to move them after they have already been in the sand for several hours. Great care is taken to make sure that the eggs are protected from the baking hot sun by a shade cloth whilst the mother lays the rest. Monitors also make sure not to shake the eggs around too much when relocating them. Either a slow walk or golf car ride will then ensure that the eggs are taken to the turtle hatchery where whoever was handling the eggs would then have to dig a nest.
The nest must emulate that of the turtle, with a bowl at the bottom and a chamber towards the top. You would not believe how much the shape of the nest impacts the survival rate of the hatchlings inside it. Should the nest be too deep, they struggle to get out. Should the chamber be too wide, the pulsing movement that helps the little turtles emerge won’t work to full effect and also cause the tiny hatchlings to struggle. Once the person has dug the nest, the eggs are carefully placed in it and then covered in sand.
In 50 days’ time, we will revisit these nests to put a fence around them. In the hatchery, the fence is purely used to allow researchers to count how many little turtles have emerged from a particular nest. In the wild or in situ nests, this little fence also serves as a line of defense against the Ghost crabs. These scary looking crustaceans will eat absolutely anything but seem to love little turtles in particular. From day 50, nests are checked every morning and evening on the first and last walks of the day. They are most likely to emerge at this time, although they will sometimes also emerge when the temperature drops during the day due to a storm.
The emergence process is amazing. It can start three days before we see the little ones at the surface, with eggs hatching below and those hatchlings moving up in the chamber. Sometimes, you can see the heads of the little ones peeping out when the emergence is going to happen, but the ones at the top have already done their hard work so they opt for a nap.
The little turtles below begin to push up against them in an event known as pulsing. The sand around the nest becomes hot due to all the activity, as the turtles rigorously push towards the surface. Sometimes, from the beginning of the pulse, it only takes a few minutes for around 100 little turtles to emerge. The sleeping hatchlings are eventually woken up by the movement caused by their kin and then, they are ready to be released.
On Cousine Island, we move them from their nest into a bucket dusted with sand. We then take them to the beach and do a controlled release, watching the hatchlings with an eagle eye and chasing away any Ghost crabs trying to make a meal of them. We would release them fairly far up the beach because that walk into the water is thought to be an important developmental moment for these tiny creatures.
It is likely that this rush to the water is the last time that any male turtles in the batch will ever find themselves on land. For the females, they will wait up to 30 years before returning to the same area to lay their own eggs one day. As the last hatchling enters the water, it is always hard not to feel like a proud parent as we send them out into the world.
Along with the pride however also comes a sense of trepidation, with only 1 in 1 000 hatchlings reaching adulthood in the wild. It is for this very reason that people around the world come together to help turtles, for it seems that at every step of their journey they need to defy the odds just to survive. Next week, I’ll be sharing some of the weird and wonderful things I watched turtles do during my time in the Seychelles.