TurtleSense Disguises a Sensor Package as a Loggerhead Egg to Predict When Turtles Will Emerge

Researchers from the University of Virginia, Hampden-Sydney College, Hatteras Island Ocean Center, IBM Research-Almaden, and Nerds Without Borders have developed a system for monitoring sea turtle nests around hatching time — by disguising the TurtleSense hardware as an egg.

"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," Erin Clabough, co-lead researcher on the project, explains. "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 TurtleSense system itself is built around off-the-shelf hardware: an Analog Devices three-axis accelerometer, on a SparkFun breakout board in the prototype, which includes a digital thermometer for temperature measurements, and a Texas Instruments MSP430F2013 microcontroller connected to a cellular modem — a repurposed low-cost cellular phone, in the original design — to send collected data via SMS messaging.

The communications hardware is too bulky to convincingly masquerade as a turtle egg, while the sensor package alone would be small enough to risk being washed out to sea and lost if not tethered, so the team split the hardware into two. The accelerometer is sealed inside a polyurethane sphere molded from a ping-pong ball, handily the size, shape, and color of a loggerhead turtle egg, with a wire connecting it to the processing and communications system housed in a sealed plastic pipe encased in a bucket of concrete. In total, the team calculates the entire build at around $300 — $250 for the communications side and just $50 per sensor.

During field tests of an upgraded version with commercial cellular hardware often found inside vending machines for stock level communication purposes, which began in 2013, the system monitored a total of 74 sea turtles nests — with the TurtleSense system undergoing revisions to boost maximum cable length, lower the power requirements, and increase the robustness to better handle the often harsh seaside climates in which the nests are dug. The current design, the team explains, includes field-repairable features and optional solar power for longer monitoring periods.

"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," co-lead researcher Samuel Wantman explains of the team's findings. "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."

The study detailing the team's findings is available under open-access terms in the journal PLOS One; an earlier paper detailing the design of the TurtleSense system was published in the Proceedings of the 16th International Conference on Human-Computer Interaction with Mobile Devices & Services (MobileHCI '14) under closed-access terms.