Statia‘s sea turtles 1: Species, sex & individuals

Our first article about Statia’s sea turtles focuses on how to identify turtles, from species via sex to individuals, and how to support science and conservation regarding sea turtles around St. Eustatius (Caribbean Netherlands) and beyond:

Turtles are among the favourites of many divers around the world. Before explaining how exactly you can help with photo identification of Statia‘s sea turtles, we‘d like to dive right into the scene.

Statia: As relaxed as

Life on the Caribbean island St. Eustatius with its 21 km² follows its own pace (Go Statia: Why visit this Dutch Caribbean island). Even at „rush hour“ everybody takes their time to greet – by waving or honking the horn – people and cars alike. When in any doubt, about who has right of way, it is generously given. Very considerate, and as relaxed as it can be.

When we were exploring the dive sites in the marine park surrounding the island from the high-water mark down to 30 metres of depths for the first time in 2014, we didn‘t expect to find the same relaxed attitude underwater. As a dive guide in the Philippines as well as the Andaman islands I was used to sea turtles, also known as marine turtles, taking off as soon as divers were coming their way. Or at least, choosing a different route to avoid the bubble-blowing humans as much as possible.

Statia‘s sea turtles

Hence, we were over the moon when Hawksbills and Greens, the most common sea turtles around Statia, were just hanging out – divers or no divers. „Ja, man“ popped up in my head every time they lifted their gaze towards me, only to take another massive bite out of one of the many sponges colouring the reefs around Statia after nodding in my direction. Sponges are the preferred diet of hawksbills even though they also eat cnidarians such as soft corals or jellyfish.

By contrast, green turtles, named after their green-coloured body fat and flesh, are strict herbivores once they reach a certain age and size. No matter if we spotted them grazing on the seagrass or while they were resting, we could approach them closely without any problems. In other places, it helps to hold a camera in front of our face to disguise the eye as well as avoid locking and swimming straight at them. Trying to imitate the slow paddling motions of their flippers with our arms can do the trick to calm and interest otherwise skittish turtles. However, Statia‘s sea turtles were as relaxed as can be already anyway.

Turtle identification: Up close

One day I was heading back towards the mooring line along the top of Barracuda Reef when a turtle leisurely approached the dive group. As it was coming closer, I took notice of its rugged carapace and its pointed and protruding beak, resembling a bird of prey, clearly marking it as a hawksbill sea turtle (filmed off Bali, not Statia but a Hawksbill in Take a Minute to Relax VIII). In contrast to hawksbills, green sea turtles have very smooth and shiny carapaces and a more rounded face with a flat beak. „How sharp is the beak of this hawksbill“ I started to wonder as it kept swimming towards me. Only centimetres in front of my mask it finally stopped to look deeply into my eyes. As sea turtles can at least live up to 50-60 years I definitely saw some wisdom in these eyes.

Awestruck I moved to the side, giving this turtle the space to follow its path while inspecting each and every diver up close. During the following months, I experienced turtles as curious and relaxed as this one every once in a while. Contrary to the traffic experiences on land, some even bumped into divers blocking their way, especially during night dives at the Chien Tong. Since we came back last year, we happily say: Nothing much has changed. From time to time, one of Statia‘s sea turtles comes up close. Maybe for human identification … In any case, I wave to greet it as I feel like a true Statian.

Identify species and sex of sea turtles

All turtles are a part of the order reptiles, scientifically named Testudines. Within this order, sea or marine turtles belong to the superfamily Chelonioidea, and are the only reptiles known to migrate long distances. Worldwide there are seven species of sea turtles. Green, loggerhead, Kemp’s ridley, olive ridley, hawksbill and flatback sea turtle are all within the family of Cheloniidae whereas the leatherback sea turtle forms its own family Dermochelyidae.

While the flatback is only found around Australia the other six species are all present in Caribbean waters. However, the kemp‘s (Lepidochelys kempii) and olive ridleys (Lepidochelys olivacea) aren‘t residents or even frequent visitors of the Caribbean islands. Even though leatherbacks (Dermochelys coriacea) pass our waters, they prefer to roam the open ocean feeding on jellyfish rather than visiting coral reefs around islands like Sint Eustatius.

However, as the nesting season of leatherbacks just started there is a chance to spot one within the next weeks. Equally elusive are loggerhead sea turtles (Caretta caretta) though sightings of these species are reported every once in a while. The most common species of sea turtles around Statia are the green (Chelonia mydas) and the hawksbill (Eretmochelys imbricata) which can be identified by their carapace, face and dietary preference (see above).

An easy way to distinguish between the sexes of any sea turtle is to check the size of their tail. When it’s long and thick, it’s a male. When it’s short, hardly sticking out from underneath the carapace, it’s a female. Other than reproduction purposes with male sea turtles, the tails are used for stirring  – in the same way as the hind flippers.

To identify individual sea turtles we need to focus on another part of their body though.

STENAPA‘s sea turtle identification project

Identifying individual animals allows STENAPA (St. Eustatius National Parks) to gather information about their moving patterns and preferences. Such data is helping scientists and conservationists to better understand the life cycle and behaviour of the animal in question.

Up to recent years, turtles have been tagged with little markers on their flippers. One quick and easy way to tag females is when they are coming up the beaches to nest. The other option of catching and releasing the turtle into the water, even carefully done, can cause stress to any individual. As bigger electronic equipment attached to marine animals can be quite a burden, in particular for smaller individuals, since it breaks up the hydrodynamic shape of the creature.

But now there is a less invasive way to track Statia‘s sea turtles. Photo ID allows identifying and tracking individual turtles without ever touching them. And every diver and snorkeler with a camera can help to collect data. Just don‘t touch or harass them!

The scales on the side of the face of any turtle are as individual as a fingerprint. As shown in the pictures above, a front or back portrait won‘t work. Ideally, both sides of the turtle‘s face are photographed, but it will also work fine with just one. The more pictures we all send, the better the algorithm gets.

Share your photos: seaturtle@statiapark.org 

Whenever possible add the time, date and dive site the picture was taken. If you don‘t have that (exact) data anymore, don‘t worry. Every entry helps. If you are filming, just take a screenshot of the side profile. Make sure you credit your picture before handing it in as STENAPA doesn‘t have the capacity to keep track of the source of all photographs.

The bigger the database, the more precisely STENAPA can follow Statia‘s sea turtles around the island and maybe even the whole Caribbean if databases are linked with other islands in the future. Thank you for your interest and participation!

Sources:

More information on sea turtles in general and each species, in particular, can be found on Ocean – Find your blue 
A good introduction to sea turtles as well as links to human activities is available on Wikipedia
Learn more about the Sea Turtle Conservation Program on St. Eustatius