The MOTUS Wildlife Tracking System has been specifically designed to track the movements of smaller animals, such as bats and birds. The system uses coded VHF radio tags, which enable us to identify and track individual animals. There are 45 receiving stations along the Dutch coast, 43 of which are maintained by Wageningen University & Research. Thanks to this network, we are able to study the the migration of bats and birds along the coast and over sea.
The tags are lightweight: the smallest is now 0.16 grams. This makes the system ideally suited for tracking small species such as bats, songbirds and even some species of insect. Depending on their weight and pulse frequency, the tags have a battery life of several weeks to even several years.
The system uses a network of stationary automated receiving stations. A map of the receiver network around the southern North Sea looks like this:
A collaborative and international network of researchers makes use of the MOTUS network. Any team can add receiving stations to the system. Because the same frequency is used, animals can be tracked over vast distances and long periods of time. In Europe 150.1 MHz is used as a common frequency. The detection range of a receiving station is usually between 2 and 15 km, and depends on the height of the receiving station, the flight altitude of the tagged animal, the habitat and the weather conditions.
The flight path of the tagged animal can be roughly assessed by connecting the locations of the receiving stations where the animal has been successively detected. It is also possible (if the receiving stations are relatively close to each other) to determine a more accurate route by means of triangulation of the received signals of different receiving stations. The network now consists of 900 receiving stations worldwide and more than 24,000 animals have been tagged so far.
You can view the data collected on https://motus.org.