The Leatherback Turtles of Trinidad

Is there another animal that appears more often in human mythology, folklore, and literature than the turtle and its land dwelling cousin, the tortoise? They have variously stood for wisdom, tenacity, longevity, fertility, or stability in cultures around the world. The leatherback is the largest of all living turtles, the male up to 900 kgs and 3 m. It feeds mostly on jellyfish and lives up to 45 years (a disputed number). Unlike other turtles, it lacks a bony shell but has a hard leathery skin. That plus its powerful flippers and hydrodynamic body allow it to dive down to 1400 m and swim as fast as 35 kmph. Given its large size, its natural predators include only sharks, killer whales, and now humans.

Surviving as a species for an astounding 150 million years (modern humans arrived 0.2 million years ago), through big extinction events like the one that killed the dinosaurs, it is now endangered by human activity: entrapment in commercial fishing gear; poaching for meat on nesting beaches; consumption of turtle eggs as a delicacy or for their (non-existent) aphrodisiacal properties; coastal development near nesting sites (lights, noise, and worse); and the turtles mistaking marine plastic waste for jellyfish.

The leatherbacks often travel thousands of miles each year to feeding sites. They mate at sea and while the male never returns to land, the female, quite amazingly, returns to spawn on the very beach where she was born. Most scientific studies are therefore based on the female. How she returns to her birthplace without a GPS device is not conclusive, though the best theories posit at least a sensory apparatus for the earth’s magnetic field, not unlike many migratory birds. Quite possibly, the geomagnetic coordinates of their natal beach are encoded into the hatchlings long before they reach the sea, and the adult female navigates to it the rest of her life. Indeed, the leatherbacks we saw were all returning to their ancestral home. So the loss of turtle nesting habitat has led directly to a decline in their numbers. This has led to more jellyfish, which eat large quantities of fish larvae, contributing to a drop in fish populations.