For many conservationists, butterflies are some of the key species that can indicate the quality of an environment not only for themselves but for many other, often less visible, species. Some of their specific needs are often well known, but movements around their habitat and important factors within it are less understood. To help address this issue, a new study reports for the first time the flight paths of five butterfly species successfully tracked using harmonic radar within an agricultural landscape. (Figure 1Figure 1On track: Radar has been used to follow the flight paths of several species of butterfly and may help to determine their environmental needs and those of other less-visible species. (Photograph shows a small tortoiseshell butterfly, Aglais urticae, carrying a transponder. Courtesy of Elizabeth Cant.)View Large Image | View Hi-Res Image | Download PowerPoint Slide) Until now, butterfly mobility has been predominantly studied using visual observations and mark–recapture experiments. But Elizabeth Cant and colleagues at Rothamsted Research and the University of Greenwich in the UK, report in the Proceedings of the Royal Society (published online) experiments in which a lightweight radar transponder was attached to the butterfly’s thorax to track their flight. They found, in initial experiments, that the transponder did not significantly affect behaviour or mobility. On release, the butterflies’ tracks were analysed for straightness, duration, displacement, ground speed, foraging and the influence of linear landscape features on flight direction.Two main styles of track were identified: fast linear flight and slower nonlinear flights involving a period of foraging and/or looped sections of flight. These loops potentially perform an orientation function, and were often associated with areas of forage.In the absence of forage, linear features did not provide a guiding effect on flight direction, and only dense treelines were perceived as barriers. The presence of fences and other landscape features did not appear to influence the flight of the butterflies, and neither did wind direction. They suggest that man-made features do not impede the butterflies’ assessment of suitable habitat.This study provides support for the non-random dispersal of these butterflies and a perceptual range of 100–200m. It demonstrates a methodology that may be of value for future investigations of butterfly mobility and ecological needs of wider environmental importance.