Crossband Transponder System and Harmonic Radar System To Track and Monitor Small Animals Over Long Time Scales

Earthspan, Incorporated, Baltimore MD

Investigators

Abstract

This award supports further development of a system for tracking of small animals and of other types of organisms as small as insects and seeds. The system makes use of a radar transmitter/receiver to trigger either of two types of small devices that will be used to tag individuals. Cross-Band Transponder (CBT) tags consist of a small battery and a microcircuit that sends a VHF radio signal in response to the triggering radar signal. The VHF signal, which will provide identifying information unique to each individual tag, will be detected using an array of conventional directional antennas. As planned, the CBT tags will weigh 1 gram, last for at year and be useful over a range extending to about 2 kilometers from the radar set and antenna array. Tags of this size should be useful with animals weighing as little at 20 grams. Harmonic Radar (HR) tags use the power of the same incoming radar signal to generate a outgoing radar signal at twice the incoming frequency. As they require no power source, their lifetime is unlimited. The signal strength is limited by the strength of the incoming radar signal, and thus the range is dictated by the cost and portability of the radar set to be used. As planned, these tags may be used on organisms (or objects) weighing as little as 50 milligrams, and over a range of up to 700 meters. The signals will not allow individual tags to be differentiated. As part of this project, the use of HR tags to monitor seed dispersal will be tried for the first time. With the development of biotelemetry technology, researchers have been able to monitor movement of individual organisms at multiple spatial and temporal scales ranging from meters and hours to thousands of kilometers and many years. This has led to new insights into the study of organism movement, and has been applied successfully for management and conservation purposes. Depending on the desired range and lifetime, existing biotelemetry tags typically require a relatively heavy power source. Thus, useful application of the technology has been limited to relatively large organisms whose ability to move is not impaired by the size and weight of the tag. The proposed system, if successful, will lead to a substantial increase in the types of organisms that can be monitored through biotelemetry, and an increase in the time period over which individual animals can be monitored without the effort and expense of recapturing the animal to apply a new tag.