Terrestrial Tracking

Advances in Global Positioning System (GPS) and satellite technology have revolutionized terrestrial movement studies. Most land-based organisms studied by Smithsonian Institution scientists, from reticulated giraffe to scimitar-horned oryx, are tracked using GPS technology. With these data, scientists are able to learn many exciting things, such as how much area an individual needs to survive or how they respond to infrastructural development. By combining data collected by GPS with satellite imagery, scientists can also understand the resource needs of individual species.

Battery or solar-powered tracking devices communicate with the freely accessible global navigation satellite system that encircle the earth. Defined by the researcher, devices are pre-scheduled to record the individual’s location at designated intervals. These intervals effect the scale at which an animal can be monitored, which also effect the length of time that the device will continue to function. Modern GPS units, for example, can collect about 2 years of data when programmed to collect a position every hour (24 positions per day). Positional accuracy of these units is generally about 2-5 meters, but is dependent on the habitat and the orbit of the satellite constellation at the time of communication.

Once a position is collected, it is stored within the unit’s memory. Many options exist to transmit the data. Some collars (store-on-board) must be recovered for data to be downloaded. Others collars (GSM enabled) transmit data via the cellular phone network. In remote locations, satellite communication networks (Iridium or GlobalStar) offer the best option to transmit positional information collected by the collar. This method, which offers 2-way communication, is also the most expensive.

In 2018, Smithsonian scientists began testing new prototype GPS tags on Przewalski’s horse and scimitar-horned oryx. These devices, which are designed to fit on the tail and/or horn of the animal (respectively), are aimed to reduce the potential adverse effects of fitting an animal with a traditional GPS collar. While still in the development stage, these devices show promise as an alternative method for increasing our understanding of animal movement.