for National Geographic News
This story is one of a series looking at National Geographic Crittercam research. Crittercam is a research instrument worn by wild animals and equipped with a video camera and other information-gathering equipment. (Get the basics on underwater and terrestrial Crittercams.)
In 1989 some 1,400 leatherback sea turtles (Dermochelys coriacea) heaved themselves ashore to nest at Playa Grande beach in Costa Rica's Las Baulas National Marine Park. By 1995 the number emerging from the surf to deposit their eggs was less than half this number. Last year fewer than 50 females waded on to the beach.
Those shocking figures reflect a worldwide trendfrequently snagged in fishing nets, leatherbacks may have declined by as much as 95 percent in the last two decades or so.
Nesting is one of the few times that female leatherbacks, which often grow to the size of an office desk, ever leave the ocean. These nesting bouts allow researchers a rare opportunity to gauge their health and population numbers.
Over the last few years, scientists working with a National Geographic Crittercam team in Costa Rica have attached underwater Crittercams to leatherbacks, documenting the world's largest living reptile in its seldom seen underwater environment. The resulting footage has shed light on rarely seen mating behavior, captured on film perhaps for the first time.
"Most of what we know about leatherbacks is from the beaches," said Richard Reina, star scientist in the Crittercam: Leatherback Sea Turtles documentary and one of several principal investigators who have worked to save Costa Rica's nesting turtles since 1988. "Now, Crittercam has given us a great perspective on what leatherbacks do in the undersea environment."
Leatherbacks migrate across entire oceans and dive as deep as whales, making them nearly impossible to find and study. Once hatched, females return to their hatching beach every few years to deposit eggs. Males never come ashore again.
Attaching an unobtrusive camera to a landed female offered an opportunity difficult for researchers to ignore.
Reina, a conservation lecturer at Monash University in Melbourne, Australia, is part of the team that monitors and electronically tags Las Baulas's leatherbacks. The coastal park (four miles, or six kilometers, long) is one of around seven major nesting sites left worldwide, and the largest in the Pacific Ocean.
Reina and his colleagues assess the status of the population and protect it from poachers and predators. The researchers' painstaking work has helped alert the world to the species's dramatic decline.