The night watch

In Costa Rica, protecting endangered sea turtles can be a beautiful experience.

Illustration by Emily Chandler

Illustration by Emily Chandler


Field Studies is a monthly column by Clare Watson, who travels around Australia and the world exploring science by participating in studies, visiting research institutes, going on trips with scientists, and a lot more.

Friday, November 13th, 2015

The alarm broke our sleep abruptly. We tumbled out of our bunk beds and fumbled to find our black clothes for the night shift. The jeep was waiting for us. We piled into the tray, sitting shoulder-to-shoulder on splintered bench seats, and bounced along the dirt road. The radio from the cab was faint. A gate was opened; we turned into a field that was as potholed as the road. The jeep slowed as dirt turned to sand.

I’ll admit, we’d volunteered for this. Sea turtles come ashore during the night to lay their eggs and it’s the perfect opportunity to survey their local populations. While passing through Costa Rica last year, my boyfriend Dean and I had volunteered to join a night turtle-nesting patrol with the Corcovado Foundation. Named after a small yet mighty national park on the Pacific coast of Costa Rica, the Corcovado Foundation promotes environmental education, community engagement and sustainable tourism to protect the unique natural diversity of the Osa Peninsula.

Sea turtles are solitary creatures that each roam our oceans for decades. As we learnt from Finding Nemo, turtles can travel hundreds and thousands of kilometres following the currents of the sea: “I need to get to the East Australian Current — the EAC?” “Dude, you’re riding it!” Yet females will faithfully return to the same beach each year to nest. Under the cover of darkness turtles heave themselves up into the sand dunes — they may be majestic in the water but they aren’t so adept on land, returning only to their evolutionary land-based roots out of necessity to lay their eggs.

The Corcovado Foundation’s Sea Turtle Conservation Program is now in its 11th year of studying nesting populations to learn more about sea turtle behaviour, like their annual migration patterns, and assessing how their nest protection programs are helping these endangered creatures. Every night in nesting season, turtles at Rio Oro are measured and tagged so that they can be identified if they return.

We traversed the beach with red-coloured head torches. Time hung over midnight. It was quiet except for the waves tumbling into shore and our incessant sniffling with the humidity. The heavy heat never abates in Costa Rica, not even at night. Kicking sand with each foot as we walked, we sprayed bioluminescent plankton and triggered them to glow white-blue, a momentary reflection of the stars in the sky. We zigzagged back and forth looking for tracks, and where we had passed by just minutes before, they would appear and we would follow them into the dunes.

I’d been told that sea turtles fall into a ‘trance’ while they’re laying their eggs. Widely documented but not entirely understood, this trance-like state is thought to be induced by the large release of hormones that trigger the first contractions of a mother’s reproductive tract once she has finished digging the nest chamber. As a biologist I believed this, I was intrigued by this, but it was still astonishing to witness.

The first turtle we encountered that night was a green turtle, una tortuga verde. I remember the dexterity of this turtle using her back flippers to expertly scoop out a narrow, deep hole to shelter her young. She was almost as wide as she was long (89cm by 86cm) — so large that I had to straddle her shell to measure it and she didn’t stop work let alone flinch. Swapping stories with Sean Williamson, a PhD student at Monash University, I learned he could trump my experience, once collecting eggs from beneath a 3m salt water crocodile whilst it was in a birthing trance.

Sean is currently researching the physiology of reproduction in reptiles. His studies have taken him to the Kimberley region in Western Australia, Heron Island on the Great Barrier Reef and most recently Costa Rica, where he was lucky to witness an arribada (Spanish for “arrival”) — a synchronised mass nesting emergence. We’re talking hundreds of thousands of turtles, which are usually solitary creatures, on the same beach — and it can occur during broad daylight several times a year. It is observed only in two species of sea turtle, the olive ridley and the Kemp’s ridley.

Sea turtles are just one curiosity of the Corcovado National Park. In four days on the Osa Peninsula, Dean and I also spotted scarlet macaws, toucans, an anteater and a troop of white-faced monkeys (not to mention all the insects). The peninsula has been described as one of the most biologically intense place on the planet, and rightly so — it houses 2.5% of the world’s total biodiversity in an area roughly 25 times smaller than greater Sydney.

Our time on the Osa Peninsula was brief but the Corcovado National Park is like no other national park that I have visited. Where Yosemite’s beauty is stunning yet accessible, the Corcovado’s riches are hidden in a seemingly impenetrable dense jungle; where Uluru-Kata Tjuta is an icon of our sunburnt country, the Corcovado is a little known pocket on the Osa Peninsula of Costa Rica; and where Torres del Paine with its brutal weather feels like you’re facing the end of the earth, the crushing biodiversity (and humidity) of the Corcovado feels like you’re in the heart of it.



Thank you to Sean Williamson for sharing his in-depth knowledge of reptiles for this story. Sean spent several months in Costa Rica working with The Leatherback Trust and in that time visited the Corcovado National Park himself.

Edited by Jack Scanlan