Marine turtles spend most of their lives in the vast ocean, but much about their migratory paths remains a mystery. Now, satellites are aiding scientists in tracking their movements during the elusive “lost years.”
In early June 2024, an adult female leatherback turtle was resting on a sandy beach along the Caribbean coast. After laying about 80 eggs and having a satellite transmitter attached to her back, she began a long journey across the ocean. She was part of an intense ocean marathon where multiple female leatherbacks are tracked to see which one swims the longest distance.
This female turtle is estimated to be at least 20 years old, possibly even up to 80 or 90. Determining the exact age of a live sea turtle is currently not possible. Although the tracking event lasts three months, a full migration from one nesting season to the next can take up to two years. So far, she has been laying between 70 and 90 eggs each time she nests and could nest four to seven times in a season. Over three nesting seasons, she may have laid between 840 and 1,890 eggs since first being observed nesting in 2020.
Scientists have been tracking sea turtles for over 20 years, monitoring their movements and migration patterns. Last year, a loggerhead turtle ventured further north than ever recorded before. Turtles are now exploring areas they didn’t commonly go to in the past, expanding their range and discovering new habitats they either couldn’t reach before or didn’t prefer.
Most species of sea turtles are sensitive to temperature, so the areas they can travel to are limited. These loggerhead turtles venturing far north indicate that water temperatures in those regions have increased, making them more suitable for turtle survival.
Healthy seas are crucial for oxygen production—experts estimate that 50% of the world’s oxygen comes from the ocean. Sea turtles are considered keystone species, playing a vital role in maintaining the health of marine ecosystems. Green turtles act as reef gardeners by grazing on seagrass beds, which helps maintain a healthy nutrient cycle. Hawksbill turtles control sponge populations, allowing space for corals to grow. Leatherbacks prey on jellyfish, keeping their numbers in check.
Turtles also serve as important biological transporters, carrying marine nutrients to land and leaving nutrients after nesting. Both the turtles and their eggs are important food sources for other animals. Their disappearance can create a cascade of negative impacts on marine and beach ecosystems. Currently, all sea turtle species are threatened with extinction, with six classified as vulnerable, endangered, or critically endangered by conservation authorities.
Sea turtles face multiple dangers across different life stages and habitats. Although they spend most of their lives in the water, there are still significant knowledge gaps about this part of their existence. A study in 2021 found that only about 20% of research papers explored climate impacts on sea turtles in the ocean, and less than 5% focused on turtles’ distribution at sea.
A marine conservation biologist has been studying sea turtles’ behavior in the ocean to identify threats. Using scientific evidence, efforts are being made to design marine protected areas. Satellite telemetry has been one of the most helpful tools in sea turtle conservation.
By using satellites to track individual turtles, scientists have identified important hotspots like foraging areas, migratory corridors, and breeding grounds. Understanding their spatial distribution is key. Combining this information with data such as sea surface temperature, fisheries and boat activity, and chlorophyll concentration—a sign of phytoplankton levels that can influence nesting—researchers can maximize information on turtles’ exposure to stressors.
For example, in a 2018 project, researchers identified areas heavily used by threatened juvenile green turtles in the waters around the Bahamas. These habitats were being severely degraded by coastal development. They divided the study area into one-square-kilometer grid cells and filled them with information about turtle density, local stakeholder use, and more. This allowed them to prioritize areas of high conservation value for the turtles and their prey while also considering the impact on the local community, costs, and other socioeconomic factors.
This valuable information wouldn’t be obtainable without electronic tracking devices. Many trackers are controlled by a microprocessor programmed before being attached to the turtles. Information is sent to satellites orbiting the poles, which then relay data back to researchers. Satellite trackers are advantageous because they don’t need to be retrieved; scientists can monitor turtles remotely from their computers.
With climate change, there might be shifts in the distribution of sea turtles as their habitat and food availability are affected. Climate change is described as a threat multiplier since it interacts with and intensifies almost all other stressors sea turtles face.
A marine ecologist has been following turtles via satellites for about 35 years and has witnessed the evolution of the technology. In the last decade, satellite tracking has improved significantly. Devices are more robust and reliable, and better methods have been developed to keep tags attached. There’s been a huge increase in the amount of data that can potentially be used to help drive the conservation of sea turtles.
Some satellite data have already been used effectively. A study outlined examples around the world, including species recovery policies, strengthening marine park zoning, regulations restricting the use of gillnets to nighttime when turtles are resting, and agreements between countries to create and protect corridors in the ocean.
More recently, researchers compiled one of the world’s largest single-species satellite tracking datasets, specifically for flatback turtles, which are native to northern Australia and classified as vulnerable. The authors created detailed distribution maps and identified areas where protective measures would benefit multiple populations at once. Importantly, they also found that flatbacks spent 99.5% of their time in Australian waters, making this a unique opportunity to conserve a marine turtle species through national and regional conservation measures.
However, other species, like the leatherback turtle, are global travelers. The number of leatherbacks is declining in many places because they wander all over the oceans chasing jellyfish, which may also be moving further due to climate change. This elusiveness makes them harder to protect since they spend much of their time in international waters where there is no regulation.
Approximately 3% of the global ocean is protected in marine protected areas, but this can only happen in areas where countries have control. Exclusive economic zones, where a nation has jurisdiction, only extend 200 nautical miles from their coasts. The vast majority of the ocean is international waters, often referred to as the “high seas,” where regulations are limited. After years of negotiations, countries signed an international treaty that provides a legal framework for addressing various stressors affecting the marine environment in these areas. This development brings hope that data collected about turtles’ movements and behaviors could help in their conservation.
A marine biologist elaborates on work and experiences finding and capturing turtles at sea, and the challenges of carefully attaching transmitters to them. On one occasion, while on a boat off the Pacific coast, the biologist and assistants waited patiently for a sea turtle to surface. When a pair of olive ridley turtles finally appeared, they dove in, wrestling underwater with the female who was trying to avoid capture. When they got close enough to the boat, the team lifted the 45-kilogram turtle aboard and covered her eyes with a dark, damp cloth to help reduce her stress.
Back on land, and despite bleeding from scratches, the team proceeded to restrain the turtle, clean the surface of the carapace, and prepare an extremely sticky epoxy resin used to attach the transmitter. They only had a few minutes to mold it because once it dries, it’s almost impossible to remove. The resin frequently sticks to clothes, hair, nails, and equipment. Some colleagues have even accidentally stuck themselves to a turtle. The process continued as they attached the transmitter, waited for it to harden, and eventually released the turtle back into the area where they found her.
Throughout this work, it’s clear that much remains unknown about sea turtles. More research is needed on migrations because, in most cases—for adults at least—they have very distinct foraging and nesting areas, and they travel between those back and forth. Understanding how a turtle gets from one country to another is crucial, and satellite transmitters help fill in these blanks.
Sea turtles have remarkable navigation skills, using the Earth’s magnetic field to travel thousands of miles and return to the beaches where they hatched. Some species, like the green turtle, can live up to 80 years in the wild. Despite their longevity, they face numerous threats throughout their lives.
Back in the ocean marathon, the female leatherback turtle is firmly in the lead, having already traveled over 5,500 kilometers. The latest information shows her foraging near the northeastern coast of the United States.
In the coming months, she might stay within the North Atlantic or cross the ocean to the Azores and the coast of Western Europe. For turtles like her, conservation remains a challenge.
Despite increasing numbers in some turtle populations, there are still significant threats and uncertainties about where turtles are living their lives. It’s no time for complacency. Sea turtles play a vital role in maintaining the health of marine ecosystems. By continuing to use satellite tracking and other advanced technologies, scientists hope to better understand these magnificent creatures and protect them for future generations.