Effective ecosystem management planning must include comprehensive natural history information of extremely small animal species, highly mobile and wide ranging species, as well as threatened and endangered animal species in order to understand and accommodate their ecological requirements. Acquiring accurate scientific information about free ranging organisms is a difficult but essential process to understand a species’ natural history. Scientists seek to design, test, and demonstrate (on a pilot scale) remote biotelemetry technologies that enable the collection of natural history information for target animal species on military installations. Current technologies limit small radiotag operating lives to a few weeks restricting study opportunities. This project will develop and evaluate the potential of crossband transponder technology to track regional and local movements of small threatened, endangered, and sensitive species (such as birds and bats) over periods of months or years for risk assessment and ecosystem management.

Schematic of Crossband Transponder

Technical Approach

Scientists are designing a means to detect and track birds tagged with a miniature transponder. A transponder is a device which transmits only in response to a specific radio interrogation signal. Such a tag has a much longer life in comparison with a conventional tag, which transmits continuously. Transponder tags mounted on birds will be interrogated, and replies monitored, by a customized radar system. Each tag can be individually identified by the system. The radars' transmitter uses a high-gain dish antenna at 3 GHz to focus the interrogating signal to maximize interrogation range and enable tag bearing to be established. The transponders' reply, at very high frequency (VHF), is detected by a modified radar receiver via a high-gain yagi antenna. The system will display and record the bearing and range of each tag. This system could, in the near future, provide tracking ranges of 2-4 km, with tag lives of 2 years or more for birds weighing as little as 20 g. The tracking distances for larger birds range of 8 km or more. The system would be transportable in the field by a pick-up or trailer.


A cross-band transponder system has been developed which includes small (1-2 grams), radar-activated VHF transmitters, along with a mobile radar system. The radar system activates the VHF tags on the target species, meaning that the tags only transmit when desired and when field biologists are present to collect the information, and provides location estimates via an automated computer system for up to 2 years. Operational ranges up to 10-15 km are expected. Development also continues on maximizing the output power and efficiency of the VHF transmitter portion of the tag. Tags capable of detection by ear at ground-to-ground ranges in excess of 900 meters have been demonstrated, using an appropriate radio receiver and 3-element Yagi antenna.


This technology represents a cost savings for the Department of Defense through: (1) having more effective field studies of special status species; (2) needing fewer personnel to complete these studies; and (3) reducing interference with military activities by having fewer persons in the field for shorter periods of time. These new technologies provide more frequent and more accurate animal behavior data, which will greatly enhance the collection of natural history information. Scientists will be better able to fully understand habitat requirements and other variables and evaluate these requirements in relation to issues involving land development and use.