When leatherback and hawksbill sea turtles finish laying their eggs in newly dug nests on a beach, they pull a fast one on would be egg poachers. They create trails and decoy turtle nests a distance away from their real egg caches, scientists say in a new paper.
ON THE NATURE DOCUMENTARIES, THE PROCESS OF SEA TURTLES NESTING ON THE BEACH is both charming and straightforward: Momma turtles crawl up the sand, dig a hole, deposit eggs, leave.
Except that when leatherback (Dermochelys coricea) and hawksbill sea turtles (Eretmochelys imbricata) finish depositing their eggs in their nests, they dawdle around the beach, seemingly aimlessly, before returning to the ocean.
Their seemingly random movements have a purpose, say scientists from the University of Glasgow. The’re creating decoy turtle nest and trails to deceive predators like mongooses that might poach the eggs if they can find them.
PUTTING ASIDE ASSUMPTIONS
The assumption was that the turtles’ behavior of scattering sand around on the beach was to camouflage the nest site, or to optimize conditions for egg development. But a consensus on its function is lacking, note the researchers.
But studying leatherbacks and hawksbills during visits to the Caribbean islands of Trinidad and Tobago that stretched over seven years, they found that the time and energy spent on sand scratching was substantial and exposed the mama turtles to dangers from predators and exhaustion.
In fact, the turtles “can spend longer doing this than for any other part of the elaborate nesting process,” says one of the authors, Malcolm Kennedy, professor of natural history at the university.
“Our findings strongly support the idea that they create a series of decoy nests away from the nests itself to reduce discovery of nests by predators,” he said.
DECOY TURTLE NESTS & PARENTAL “CARE”
Considering that after laying the eggs and leaving, any newly hatched turtlettes are on their own, without parental protection, the mama reptiles’ efforts to create decoy turtle nests are striking.
It’s not known whether other sea turtle species engage in this behavior.
But Dr. Campbell notes that, “Remarkably, we found similar behaviors in two species of turtle that shared a common ancestor over 100 million years ago, while dinosaurs still ruled the land. What they do must be extremely important to their offspring, which they will leave behind as eggs in the sand and never see.”
The paper, Buried treasure – “Marine turtles do not ‘disguise’ or ‘camouflage’ their nests but avoid them and create a decoy trail,” was published in the journal Royal Society Open Science.
PRINCIPAL SOURCES: Female sea turtles do not disguise their nests – but create a decoy trail, University of Glasgow News Office; “Marine turtles do not ‘disguise’ or ‘camouflage’ their nests but avoid them and create a decoy trail,” Royal Society Open Science; Mother Sea Turtles Might Be Sneakier Than They Look, New York Times.