By Nathan J. Robinson, Ph.D
Sea turtles have been swimming in our oceans ever since the time of the dinosaurs, enduring meteor collisions, ice ages, and the shifting of the continents. Yet human activity has recently brought many sea turtle populations to the brink of extinction. Even the largest of the sea turtles – the leatherback turtle, a prehistoric giant that can grow to over 2 meters in length – is rapidly vanishing from the East Pacific Ocean. This population has now declined by more than 98% in the past 25 years. In the hope of seeing populations recover, countless conservationists and volunteers work tirelessly day and night. But lest we forget, these people do not work alone, sea turtles themselves are also working hard in this struggle.
All sea turtles start their lives as small hatchlings, just a few centimetres long. Life is perilous for a hatchling; they are prey for a staggering array of birds and fish. Only those with enough luck and persistence will survive long enough for their bodies to develop, their carapace (shell) to toughen, and flippers to grow. It is estimated that only 1 in every 1,000 hatchlings will survive the 20 to 30 years it takes for a hatchling to reach adulthood. In contrast to their earlier years, adult sea turtles are armoured and rugged. While they will now only be preyed upon by killer whales and the largest of sharks, this does not mean that the sea turtles’ struggle for survival is over.
With adulthood comes the desire to reproduce and to do this sea turtles swim back to beaches near to where they were born. These migrations can extend over 10,000 km and are some of the longest in the animal kingdom. Sea turtles undertake these epic migrations to ensure that they nest on sandy tropical beaches where the conditions are just right for incubating their eggs. The energy stores required to both migrate such long distances and nest successfully are so great that sea turtles generally need between 2 to 7 years to build up enough of their energy stores for a single nesting season.
Once they make their arduous journey, a female turtle will lay hundreds of eggs in a single nesting season. Under suitable conditions, sea turtles can continue to do this for at least 40 years after reaching sexual maturity. In fact, we do not know how old sea turtles can get in the wild, because we simply have not been researching them long enough to answer this question. Furthermore, sea turtles continue to grow even after reaching sexual maturity and as they do they are able to lay more eggs than their younger counterparts. Sea turtles, like some freshwater turtles, might even exhibit negligible senescence. In other words, sea turtles don’t appear to age like us; instead, they just get bigger and better over time.
The huge investment of time and energy that sea turtles dedicate to reproduction is a testament to their innate drive for survival. Indeed, for sea turtle population to thrive each adult must produce enough hatchlings over the duration of their adult lives to ensure that, against terrible odds, at least some offspring will survive long enough to become adults themselves. While this strategy has worked for millions of years, humans are now tipping the balance.
Each year countless sea turtles are incidentally caught and killed by fisheries that are hunting for commercial species, such as tuna or swordfish. If they’re not caught by fisheries, they choke on or die after ingesting plastic bags and other plastic waste that makes its way from our homes to our oceans. And when adult sea turtles do come back to nest, they find that the once quiet, dark nesting beaches where they hatched are now lit up by hotels, restaurants, and houses.
It is our responsibility to fix these issues, be it by fishing in a smarter and less wasteful manner, reducing sound and light pollution on nesting beaches, or reducing our use of disposable plastics. This is our part in ensuring the recovery of sea turtle populations worldwide. The turtles will do the rest.
Nathan J. Robinson, Ph.D, is Field Director of The Leatherback Trust. His research focuses on investigating how large marine species, such as sea turtles, respond to oceanographic processes. He is also interested in applying novel technologies to uncover the secrets of marine megafauna and develop effective conservation management strategies. Nathan holds a Ph.D in Biology from Purdue University, USA, and a Masters in Marine Biology from Southampton University, UK.
The Leatherback Trust is a non-profit organization dedicated to saving the leatherback sea turtle. Our mission is to promote the conservation of leatherbacks and other turtles at risk of extinction.
Eastern Pacific leatherback turtles are critically endangered. This population of sea turtles has declined by more than 98% since 1990. We are working to reverse this trend by tackling the 5 most deadly threats to leatherbacks and other sea turtles around the world. Our scientists conduct research at nesting beaches and at sea, collecting critical data to support conservation interventions. We partner with communities to protect nesting beaches and work with governments to inform sustainable development and fisheries management priorities.