How Tracking Sea Turtles by Satellite Works

Why track sea turtles by satellite?

Research into the behavior and life cycle of marine turtles has taught us that these creatures do not generally nest and feed in the same area. We now know that sea turtles are highly migratory, often traveling hundreds or even thousands of miles between the beaches where they lay their eggs and the foraging (feeding) grounds where they spend much of their time at sea.

Since most research conducted on marine turtles has been carried out on nesting beaches and well over 90% of a sea turtle's life is spent in the water -- feeding, mating, migrating and doing whatever else a sea turtle does when no one is watching, we are missing important information that can help us better protect sea turtles. In particular, to adequately protect sea turtles in all their habitats, we must learn more about their migratory patterns, their behavior at sea, where their marine habitats are located, how the turtles use these different habitats, and the migration routes turtles travel between habitats.

This is where the technology of satellite telemetry becomes useful and important in protecting sea turtles. Satellite telemetry (following an object on the earth with the use of orbiting satellites) has advanced to the stage of allowing researchers to track turtles in the open ocean after attaching a Platform Terminal Transmitter (PTT) to the back of a sea turtle. The PTT sends a signal full of information to an orbiting satellite each time the turtle surfaces for air. The satellite re-transmits the data to a receiving station on earth, which researchers can access through their computer. Generally, after about a year the transmitters quit working and fall safely off the turtle. View photos of a transmitter being attached using Marine Epoxy Method & Fiberglass and Resin Method.

Before his death, Archie Carr urged young researchers to dedicate more time to studying how and where sea turtles migrate and what mechanisms they use to return from thousands of miles away to the same tiny stretch of beach. In particular, Archie lamented that the use of satellite telemetry to track turtles in the open ocean had not yet reached the required level of sophistication. Well, Archie would be pleased to see what is being done with satellite technology today to study and protect sea turtles.

How does satellite telemetry work?

The small, low wattage PTTs attached to the turtles are controlled by a micro-processor which is programmed by a computer before it is attached. The program tells the microprocessor how to store information and when to transmit the information to the satellites. Polar orbiting satellites are currently used for tracking animals. The satellites are operated by the U.S. National Oceanic and Atmospheric Organization (NOAA) and are the same satellites used to monitor global weather patterns. Attached to these satellites are special instruments operated by a French company, ARGOS CLS. These special instruments are designed to listen for transmitters like those we place on turtles and to determine where those transmitters are located. While such a task would seem simple, it is not. Each satellite circles the earth every 101 minutes and so it is only over any one place on the planet for about 10 minutes. At the equator, this means that the satellites make about 6-8 passes per day for 10 minutes each. For the satellite to determine the location of the transmitter it takes about 3-5 minutes, and the transmitter must be on the surface to be detected. However turtles rarely remain on the surface for that long, and their surfacing must coincide with the satellite passing overhead. Thus it is uncommon to receive a location from a turtle every day.

The data received from the turtle's transmitter comes in the form of digital codes, which must be deciphered. The codes allow researchers to determine, with varying degrees of reliability, the latitude and longitude location of the turtle, the number of dives taken during the last 24 hours, the duration of the most recent dive, and the water temperature.

Using computer mapping programs, or by hand plotting the location data, researchers can then visually see where the turtles are, the route they have traveled, and how fast they are generally swimming. Depending on the detail of the map one is using, a researcher can also determine the habitat characteristics at the turtle's location.

While viewing the migration maps shown on this site, viewers should be aware that the plotted turtle movements represent the best data available; however, any given plot mark may not be 100% accurate. This limitation really doesn't detract from the overall value of the research. While a particular location point may actually be miles off a given turtle's actual location, the accumulation of data stills tells us where the turtles are generally moving and where their primary foraging areas are located. Using this information, we can begin to focus conservation efforts where they are most needed.

See the Results From Early Sea Turtle Satellite Tracking

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