“What do you mean, they make… nests?” is not such an obvious question as it may initially seem to me.
One of my lecturers at University once said to me, when she was a shiny new undergrad, somebody told her that turtles build nests, and she couldn’t help but think they meant turtles roam the beaches looking for sticks to pile together.
To me, the fact that turtles dig nests on land seems like such an obvious thing, but that’s after years of going out of my way to learn about these animals and their ecology. Turtles are marine reptiles, so of course they have eggs, but when you stop to think about it – a marine creature venturing onto land to dig a nest and lay a clutch certainly is a strange phenomenon.
And when you see it happening, it seems even stranger.
A shiny wet turtle emerges from the surf, in a less than elegant manner. Immediately the prehistoric-sounding grumbles, huffs and puffs begin. Green Turtles are big, as soon as they are out of the water, the weight of their carapace begins to press down on their organs and lungs, which can’t be a nice feeling. Then commences the monumental task of hauling their colossal weight up the beach, which some Loggerhead turtles don’t bother with (for a reason that still remains a mystery to me) and decide to lay almost in the surf.
In the pitch darkness, you can hear a turtle before you can see her, whether that be because of her gurgling exhalation or her plastron crunching over plastic debris. Once the picky lady has found a spot she likes and has flicked the sand about a bit to make sure it reaches her exacting standards, she starts to dig a body-pit.
Now, what is a body pit? Simply put, it is a pit a turtle digs around her body. Turtles dig these pits by flapping their fore flippers back and forth to shift the sand around them (often in your general direction, and into your eyes and mouth… yum). These pits can be huge, and I have found the abandoned ones make nice little hiding places when you’re trying to stealthily keep an eye on a turtle in the night (but you have to be wary not to fall asleep in them).
Just because a lady has spent an hour digging a body pit, doesn’t mean she’ll stay (ohhhh no - that would be far too convenient). Often, she’ll ditch and have another roam around and try a different spot, I have observed some turtles dig up to six body pits in one nesting attempt, and as you can imagine this makes deciphering turtle tracks in the light of day an absolute nightmare. If you’re lucky she’ll dig a nice body pit in under an hour and move onto the next step, digging the egg chamber.
Again, this is essentially what it says on the tin: a chamber a turtle digs in which to lay her eggs.
Now, this is where it gets pretty awesome.
Have you ever tried to dig a 30cm across, 70cm deep, perfectly cylindrical hole on a sandy beach? If you have you know it’s bloody difficult. But it is also good to bear in mind humans have not evolved to dig perfectly cylindrical holes in the sand, and marine turtles have.
The turtles use their back flippers this time, like big webbed hands. Alternating flippers each time, they reach into the sand, scoop up a little flipper-full and flick it (again, usually into your mouth and eyes). As the hole gets deeper and deeper they reach further and further into the hole and keep scooping out little mounds of sand until the hole is anything between 50-80cm deep, sometimes even deeper!
Loggerheads dig much shallower chambers – more about this in a later post.
Guess what? Just because a lady has spent an hour digging an egg chamber, doesn’t mean she’ll stay. She can sometimes come across a rock, or the sand might be a bit too wet or a bit too dry – but usually if she’s embarked on digging an egg chamber, she’ll follow it through (for another reason that remains a mystery to me).
Now comes the super exciting (and slightly gross) bit! When my ‘turtle-y senses’ start tingling, I’ll army crawl up behind
her and wait for the greatly anticipated moment – the laying of the eggs. She’ll stop digging and her cloaca will start to move, and a few seconds later she’ll deposit up to one hundred (ish) shiny turtle eggs into the perfectly formed chamber.
This is when we can start assessing her condition, take measurements, put in temperature loggers etc. etc. – again, I’ll go into detail in another post!
After she’s laid all of her eggs, she’ll do basically the same process but in rewind. First, using her back flippers, she will carefully tuck her eggs in with an aerated sandy duvet (this is where I try not to lose the temperature logger string!).
Then using her fore flippers, she will bury her nest under a big (like, really big) mound of sand, to protect her babies from the heat, and predation.
You may think this is the hard bit over for us, she’s laid, data has been taken – job done? No.
Turtles like to nest very close together, and often will, during the nest-covering-up stage, travel around four meters forward and come across other turtle nests, nearly almost completely obliterating them. They are incredibly strong animals when flapping about (I learnt this the hard way) and will quite happily rip up and crush all of the metal cages and domes you’ve painstakingly laid over the other nests on the beach to protect them from foxes and dogs – so we need to keep a beady eye on them during this stage.
So, there you have it, marine turtles do make nests, and that is how!
Next week I’ll be writing about what data we collect in those golden moments after a turtle has laid her eggs, and how we go about collecting it (and why!)– so subscribe and stay tuned for more turtle diaries!
ALL PHOTOS AND VIDEOS ARE MY OWN