Radio telemetry is a critical technique in conservation ecology, particularly for studying the movement and range of individuals and populations. Traditionally, most radio telemetry work is done using handheld directional antennae by using either direction-finding and homing techniques, or radio-triangulation techniques. Over the past couple decades, efforts have been made to utilize aerial vehicles to make radio telemetry tracking more efficient, or cover more area. However, many these approaches require the use of manned aircraft and specialist skill sets. The proliferation of small unmanned aerial systems (SUAS) with high reliability and ease of use, as well as recent development and application of robotic sensing and estimation, opens up the possibility of leveraging SUAS to conduct radio telemetry studies. In this thesis, I present the results of five years of development as well as the testing and deployment of a drone-based radio-telemetry tracking system that is able to track multiple targets simultaneously while operating in field conditions as part of a field expedition.