Two baby sea turtles leaving trails in the sand.

Just-hatched sea turtles scurry towards the safety of the waves, leaving trails similar to those seen in newly described fossils. Credit: Cyndi Monaghan/Getty

Palaeontology

Baby sea turtles’ treks are captured in fossils

Rocks preserve prehistoric tracks that resemble those made by two modern sea-turtle species.

The first known record of baby sea turtles making their run for the ocean has been revealed by fossilized tracks dating back about 100,000 years.

After emerging from eggs buried in sandy nests, sea-turtle hatchlings race towards the ocean, which offers refuge from land-based predators. The turtles don’t return to shore until decades later, when they are breeding adults. Martin Lockley at the University of Colorado Denver and his colleagues discovered the world’s first fossil evidence of the post-hatch dash on South Africa’s Cape south coast.

Fossilized turtle tracks in sandstone.

These imprints record three hatchling turtles’ march to the sea some 100,000 years ago.Credit: Jan de Vynck

Some of the imprints resemble those made by modern loggerhead sea turtles (Caretta caretta); other traces look like those made by modern leatherback turtles (Dermochelys coriacea). Today, both these species typically nest in warmer regions more than 1,200 kilometres to the northeast, and rarely appear along the Cape south coast, suggesting that climate and sand temperatures were higher there when the tracks were made.

The authors speculate that a layer of fine, dry sand blew across the prints when they were fresh, aiding their preservation.