So how exactly do you fool an egg thief so thoroughly? Thank a material called Ninja Flex, which has a squishiness that approximates that of a sea turtle egg. By loading Ninja Flex into a 3D printer, Williams-Guillen could build an egg case that was flexible, yet strong. “After many iterations, we were able to get to something that really feels reasonably like a turtle egg and looks like a turtle egg,” says Williams-Guillen. Given that poachers are emptying turtle nests at night, feeling through the sand and relying largely on touch, they apparently fall for the ruse.

Williams-Guillen prints the InvestEGGator all in one piece. “I’m able to go in and open it with an X-ACTO knife, squish it open enough to shove the transmitter in there, and then glue that back shut,” she says. Think of this transmitter as a tiny version of your cell phone. “We really wanted it to be consumer-grade electronics, because A) we’re wildlife biologists—we’re not going to build this from scratch, a transmitter,” Williams-Guillen says. “And B) we’re wildlife biologists—we don’t have any money. So it needed to be something that was relatively inexpensive.”

They ended up with a simple transmitter equipped with GPS that also uses a regular cell connection. As a poacher transports the InvestEGGator around Costa Rica, the device connects to cell towers, giving the researchers location data once an hour. “As long as you have reasonable network coverage, then you have a reasonable chance of transmitting,” Williams-Guillen says.

Williams-Guillen and Pheasey found that while poachers tended to sell eggs locally door to door, the InvestEGGator was also able to track long-range transport—one trip was 137 kilometers long, from the beach to central Costa Rica. Pheasey could zoom in on the tracker using Google Maps and actually pinpoint that the egg was behind a supermarket, perhaps in a loading bay or back alley. “To be quite honest, there’s no real reason to be there if you’re not doing something a little bit suspicious,” Pheasey says. “I actually went and visited it, as well, sort of ground-truthed it. And yeah, it was behind a supermarket, which suggests that that’s a handover meeting point.”

From there, the InvestEGGator’s data showed that the decoy egg went to a residential property, further evidence that the supermarket was serving as a kind of illicit distribution point. “That is, again, in keeping with what we know about the trade, which is that people sell these eggs door to door,” Pheasey adds. “We were pretty happy with that result, because it really did prove the concept—this is what we’re trying to do with these things.”

Inevitably, though, their fake eggs would be exposed whenever someone would, well, try to eat one. The researchers tracked one InvestEGGator that went offline 43 kilometers from the nest where they’d buried it. A week and a half later, a different local turtle monitoring project got in touch with the researchers, passing along photos they’d received of the missing egg—now dissected. The person who’d sent them the photos was actually forthcoming about it: They said they had indeed bought sea turtle eggs, and did the group have any idea why one of them was full of electronics? “Absolutely no concern about, you know, the fact that they’d purchased turtle eggs,” says Pheasey.

But, she points out, “in Costa Rica, it’s not illegal to purchase them—it’s illegal to take them off the beach to traffic them. Which I think gave them further kind of confidence in sharing that information.”

The trafficking of eggs is but one of many compounding threats that sea turtles face. For one, they’re mistaking ocean plastics for food. And rising temperatures make for hotter sand, which is a twofold problem for the turtles: It can get so hot that the developing young perish, and because the sex of a turtle is determined by temperature at which it develops (hotter for females, cooler for males), the sex ratios of populations are shifting.