Harmonic Radar Tags for Insect Tracking: Lightweight, Low-cost, and Accessible

Using tracking devices to follow animal movements has long been a standard approach for studying the behavior and ecology of vertebrates. Until relatively recently, these tracking methods have been unavailable to entomologists due to the prohibitively large size and mass of the tracking devices that must be attached. Technologies applied to insect tracking include radio telemetry, Bluetooth, RFID, and harmonic radar. Among these, radio telemetry is the most used method to track larger insects. It offers a longer detection range and unique signals for each tracked insect but requires expensive tags that have limited shelf and field life and are heavy, generally at least 150 milligrams. By contrast, harmonic radar tags, first used in 1986, are lighter by at least an order of magnitude, inexpensive, and have detection ranges that allow field tracking of many smaller insects. Here, we demonstrate the use of an off-the-shelf transceiver marketed for backcountry rescue. Together, inexpensive tags and off-the-shelf transceivers make this insect-tracking technique highly accessible to entomologists studying insect behavior and ecology. In this article, we will touch on creating tags, attaching tags to insects, tracking these tagged insects, and present some representative tracking results.