BackTracking wildlife from space
Availability of Argos polar-orbiting satellites allowed the tracking of wildlife with a platform transmitter terminal anywhere in the world
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Many wildlife studies require an in-depth understanding of the daily activity of animals, including their movements, in order to draw inferences about their interactions with the environment or use of habitats. However, the elusive nature of the species being studied or the challenging environments where they occur often makes it difficult to gather information through direct observation. This changed with the advent of radio-telemetry technology in the 1960s and remote tracking of wildlife advanced significantly.
Using very high frequency (VHF) radio devices wildlife could be tracked remotely—but within a range of a few kilometres. It was still impossible to track species that migrated over long distances. This became possible with the availability of the Argos polar-orbiting satellites in 1978 that allowed the tracking of wildlife with a platform transmitter terminal (PTT) anywhere in the world.
PTTs are attached directly to the animal using epoxy or fibreglass and resin, or fitted as a collar, or as a backpack using a Teflon tape, depending on the species. The smaller the size of the PTT, the shorter the battery life, which influences the tracking duration. The Argos satellites pick up the signals emitted by the PTTs and relay the information to receiving stations on the ground. There, the data is processed and sent daily to researchers via the Internet, providing the locations.
Inclusion of the global positioning system (GPS) in satellite transmitters has additionally improved the quality of data. Global location sensing (GLS) devices or light-level geo-locators are a recent advancement in tracking technology. Since the time of sunrise and sunset is unique to a location on earth, the geo-locators use this to calculate the location. The calculated daily locations are stored in the tags, and to retrieve the data the bird with the tag has to be recaptured, which in many cases is impossible to do.
Continued improvements in technology and the miniaturization of PTTs have now made it possible to track smaller species. In addition, the development of PTTs equipped with solar panels to recharge batteries has extended the operational life of these kits. One such is the 5g solar PTT developed by Microwave Telemetry Inc. Introduced in 2007, this device could track small birds in the 150-250g range, and is currently offered on a limited production run basis.
The 5g solar PTT was the natural choice when it was proposed to track Amur falcons from Nagaland. The Amur falcon is a small bird of prey weighing 160-200g, and is a long distance trans-equatorial migrant, travelling from eastern Asia all the way to southern Africa and back every year, with a one-way distance of more than 20,000 km. In November, three Amur falcons were attached with PTTs in Nagaland, the first time this specialised tracker had been used in India.
For the course of a year now, the satellite tracking of Amurs has provided us with detailed insights into the lives of these incredible birds. The solar panel in the PTTs may continue to keep the transmitter alive, and it is possible to track the Amurs’ long distance journey across the Equator and back yet another time. The continued technological innovations and developments in solar cells and microelectronics are definitely set to improve the tracking devices, which will further our understanding of the movements and behaviour of many long-ranging species.
R. Suresh Kumar is a scientist at the Wildlife Institute of India and part of the Amur Falcon Partnership project.
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