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Sea turtles that hatch from human-made nests may have less well-developed brains, sexual organs and motor skills than hatchlings from natural nests.

Conservationists regularly move the eggs of endangered sea turtles when their original nest site is at risk, such as from poaching, predation or floodwaters. This is either to indoor incubation facilities or to hand-dug holes in a protected area of the same beach where they were laid. However, it is a delicate task since reptile eggs are highly sensitive to their environment.

鈥淲hen eggs are relocated to hatcheries, their chance of survival is improved. However, this also probably imposes trade-offs on developing turtles,鈥� says at Michoacan University of Saint Nicholas of Hidalgo in Mexico.

To explore what those trade-offs are, she and her colleagues identified 10 olive ridley turtle (Lepidochelys olivacea) nests with newly laid eggs on a Mexican beach. The researchers set up shelters to protect half of the nests and carefully transferred the eggs from the other half to human-dug holes elsewhere on the same beach.

When the baby turtles emerged from the sand, those from human-made nests weighed about 9 per cent less than those from natural nests. Some regions of their brains had fewer neural precursor cells and mature neurons, and the ovaries of female turtles also had fewer progenitor cells. When the researchers flipped the turtles upside down, the ones from artificial nests took more than twice as long, on average, to right themselves. Those poorer motor skills could make it harder for newly hatched turtles to evade predators while crawling to the ocean.

Even though the two nest sites in the study were close together, the team found that the sand around human-made nests was warmer and drier than the sand around the natural ones. at the University of Queensland in Australia says that the higher temperature of the human-made nests was likely to be the main factor affecting the turtles鈥� development.

The finding highlights the need to make artificial nests as similar as possible to natural ones, says Booth. Furthermore, moving eggs 鈥渟hould not be routine practice, but rather only done in exceptional circumstances when nests are in imminent danger of destruction鈥�, he says.

Mel茅ndez-Herrera says that turtles may develop more slowly in some areas because the brain and body are prioritising more important functions for staying alive. 鈥淚 am convinced that in the face of the environmental challenges, the organism does the best it can with what it has available,鈥� she says.