Egg-shaped sensor relays vital data on endangered sea turtle nests
When endangered sea turtles lay and bury eggs in a nest on a beach, that beach is often closed to the public until those eggs hatch. A nest-monitoring sensor – which looks like an egg – has been created to help predict when such beaches can be reopened.
The device is part of the TurtleSense system, which is being developed by a team led by Dr. Erin Clabough of the University of Virginia and Samuel Wantman of open research group Nerds Without Borders. It was tested during the 2013 through 2017 nesting seasons, in 74 loggerhead sea turtle nests located on North Carolina's Cape Hatteras National Seashore.
The sensor unit itself incorporates a motion-sensing accelerometer, a temperature sensor and a microprocessor, which are contained within a waterproof polyurethane sphere that is the same size, shape and coloration as a sea turtle egg. It's connected via a 6-meter (19.7-ft) electrical cable to a communications unit – the latter takes the form of a sealed PVC pipe tower containing a microprocessor, batteries and a cell phone module.
When conservation workers first spot the signs of a freshly laid nest, they carefully dig down to the top layer of eggs, gently remove them, lay the sensor in place, then replace the eggs and fill the nest back in. The communications unit sits up on top of the sand beside the nest, wirelessly relaying data from the buried sensor.
In the field studies, the sensor data indicated that there is typically a period of intense hatchling movement within the nest, followed by a pause before the baby turtles all dig their way out of the nest and head for the water. This pattern suggests that the hatchlings can sense each other's movements, allowing them to wait and then emerge as a group, lowering the chances of any one of them being killed by a predator.
"As each turtle emerges from its shell, it climbs up to join its siblings at the top of the clutch of eggs, creating a wave of commotion among all the other baby turtles in the nest," explained Wantman. "When there is no more commotion there is a period of quiet, which may be the impetus for all the hatchlings to boil out of the nest together."
Importantly, once that initial wave of commotion has been detected, it's possible to predict how long the period of quiet will last, and thus almost the exact day that the hatchlings will emerge. TurtleSense has also been shown to accurately identify non-viable nests, that no longer need to be monitored or waited upon.
"It’s absolutely magical to witness baby turtles poke their heads out of the sand and sprint towards the ocean, but it’s an event that can be very hard to predict," said Clabough. "The TurtleSense system is a low-cost, creative solution that remotely allows us to detect how baby turtles synchronize developmental movement within the nest in real time. We can use the system to detect hatching and to better predict when the hatchlings will emerge onto the beach."
The research is described in a paper that was recently published in the journal PLOS ONE.