Transmitters, also called PTTs (Platform transmitter terminals) are attached to the animal whose long distance movements are to be studied. Once they are turned on, the telemetry transmitters send high frequency signals which are received by polar orbiting weather satellites. ARGOS, a French company, has equipment on board these satellites for tracking animal movements.
The transmissions are first decoded to identify the telemetry transmitter, each of which has a unique code and then the position of the transmitter is calculated. The data is then downloaded by ARGOS. Once the data is received, the latitudes and longitudes can be plotted on a map and the migratory routes of the animals can be traced. The data is classified by ARGOS depending on the quality of the data received by the satellite. LC 1, 2 and 3 are the best quality points and have an error radius of 1000m, 350m, and 150m respectively.
In marine turtles, the telemetry transmitters also have a salt water switch which is turned on when the turtle is under water. The PTT send transmissions only when the salt water switch is turned off ie. when the turtle surfaces.
For more information, check:
ARGOS site
www.cls.fr and www.cls.fr/html/argos/wildlife/wildlife_en.html
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