TURTLES HAVE A problem. They are delicious. And so are their eggs. That has led to heavy hunting in the past. These days, though, the seven species of marine turtle are protected in most countries. If turtle soup is legally on the menu its source will be a freshwater species such as the North American snapping turtle. But that does not stop the eggs of marine turtles being poached. Which they are, frequently.

Such poaching is often ignored by local bobbies. But even if the authorities do wish to clamp down on it, arresting the small-fry who dig the eggs up on beaches where turtles nest will not deal with the problem. That requires finding the trade’s organisers. And this can be hard.

To assist the process Kim Williams-Guillén of Paso Pacifico, an American conservation charity, and Helen Pheasey of the University of Kent, in Britain, have come up with a nifty gadget. It is a global-positioning-system transmitter enclosed in a plastic shell made by 3D printing. The result looks like a turtle’s egg and weighs about the same. Dug up and carried away by poachers, it can lead the police to those poachers’ bases of operation.

As they report this week in Current Biology, Dr Williams-Guillén and Dr Pheasey have now tested their invention in Costa Rica, a place where turtle-egg poaching is rife. They set the printer to mimic the eggs of two species, the green and the olive ridley, which frequent that country’s coastlines, and placed a decoy egg into each of 101 turtle nests on four beaches where poaching is a problem. The decoys were rigged to remain dormant until their shells were exposed to the air. At that moment—presumed to signal the arrival of poachers—the “egg” in question starts broadcasting its location once an hour.

In all, 25 of the decoys were poached. They told different stories. Some travelled just a few kilometres, with one ending up at a bar 2km away from the nest it was taken from, where its signal abruptly ended. Others went quite a distance. One, for example, was carried 137km inland, to a supermarket loading bay, before transmitting its final signal from a residential property nearby.

The most curious tale, though, was told by a decoy that ended up in Cariari, a town 43km from the beach where it had been deployed. To their surprise, the researchers were sent photographs of this particular device by members of a local turtle-monitoring project. This group had been contacted by the egg’s purchaser, who was happy to volunteer where he had bought it—indicating either that he did not understand that the trade was illegal, or that he didn’t care.

To make sure that they, themselves, were not harming what they were intending to protect, the researchers monitored all of the decoy-laden nests which had survived the attentions of poachers and compared these nests’ outputs of hatchlings with those of 44 other surviving nests that had no decoy in them. Both sorts of nest had the same hatching rates, suggesting that adding a decoy did not affect the development of the eggs it was hidden among.

Given the success of their project, Dr Williams-Guillén and Dr Pheasey propose that the idea should be used more widely for turtles. They also suggest that similar decoys might help protect the eggs of other endangered reptiles—and birds—that are collected and traded illegally.

This article appeared in the Science & technology section of the print edition under the headline “How to prepare poached eggs”

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