Tracking tiny turtles

“At the Caraplace, turtle hatchlings are raised for two to three years until they're of a size that you would see them in the wild,” Rebecca says. During this phase, the turtles grow up to approximately 40 centimetres long.  “This is the phase in their lives which we call ‘the lost years’, because people usually don’t see turtles this small in the wild.”

“Sea turtles are very mysterious animals, and especially young turtles,” Rebecca says, adding that research so far has often focused more on adult turtles rather than on small juveniles.

One way to learn more about these creatures is by attaching satellite trackers to their carapace and analysing their movements. Rebecca says that attachment methods have to be specific to the size and species of turtle at hand, especially in the case of young hawksbill turtles. “This is because small juvenile hawksbills have a really bumpy shell,” she says.

Having a bumpy shell means that attaching satellite tracking devices for research purposes may be difficult. “We didn't want to put all this expensive tracking equipment on their carapace, send them out into the world, and then it would all just fall off,” Rebecca says.

So, Rebecca decided to find out how to attach a small satellite tracking device, which only weighs around 39 grams, on turtles that weighed around two to four kilograms, without making the turtles feel uncomfortable.

Tracking turtles without discomfort

Rebecca knew the importance of doing that in an ethical way, maintaining good welfare for the turtles, from previous research she had done on how to tell a happy turtle from an unhappy turtle. In this work, Rebecca examined what measures turtle rehabilitation centres had already done.

“I looked at turtle welfare in five domains: nutrition, physical health, environment, behaviour and mental state,” Rebecca says. “My main takeaway is that behaviour is actually one of the best ways to monitor welfare of turtles in rehabilitation settings. It's non-invasive, it's low cost, and it can be easily replicated.”

Rebecca also found that it is important to look at stress in turtles, which she then assessed during the replica tracker attachment study. While doing so, she found that real life turtles are not far from what is shown in the Disney movie, Finding Nemo.

“When watching Finding Nemo, you may think turtles are pretty chill,” Rebecca says. “I'd say that's accurate.” Luckily, Rebecca’s turtles didn’t mind having a replica of a satellite tracker attached to their carapace.

Once she had removed the replica tracker after three and a half months, the shell underneath was still completely healthy, and Rebecca realised that it was time to rewild the turtles. So, in May 2021, Rebecca equipped her turtles with the satellite tracking devices, and the turtles were released.

To keep pre-release stress to a minimum, it was decided that the turtles were to be released on the Great Barrier Reef off the Townsville coast. Rebecca filmed the behaviour of the turtles at release to later analyse the event.

“My aim was to compare the behaviour of the turtles raised in captivity to what wild turtles would be doing,” Rebecca says. “Our turtles were displaying naturalistic behaviours. They were swimming around, resting, investigating, and doing things that they should be doing and that you would expect them to be doing.”

Solo travellers with individual tastes

When looking at the satellite tracking data, most of her turtles were indeed very adventurous, Rebecca says. “All turtles did different things, which was really cool. About a third of them went North, a third of them went South and a third of them stayed just off the coast near the release site.”

“One of them went as far as Gladstone, and one of them was hanging around Hamilton Island in the Whitsundays. That was obviously a ‘bougie’ turtle,” Rebecca says and laughs.

“All turtles transmitted for different amounts of time, but the longest went for about 13 months,” Rebecca says, adding that the guaranteed battery life of the trackers was only three and a half months.

A future in turtle conservation

Rebecca is currently finalising her thesis “Release on good behaviour: Measuring and assessing naturalistic behaviour of juvenile hawksbill turtles (Eretmochelys imbricata) released into the wild after a period under human care”.

Once she has submitted later this year, Rebecca has a clear picture of the work she would like to do. “For me, it's important that I can use research and legitimate data to put conservation practices and management into place,” Rebecca says. “A rehabilitation group contacted me recently about my research papers and asked me to assist them in their facility implementing turtle welfare measures, which is great.”

So, even though Rebecca might not keep on tracking tiny turtles in future, her research will certainly have a positive impact on the wellbeing of turtles in Australia and beyond.