Unmanned aerial vehicles as a useful tool for investigating animal movements - samples

Determining animal abundance is crucial for assessing the effectiveness of
management measures against pest animals. Meanwhile, investigating animal
movements has become important for conducting abundance estimations of
unmarked animals since the random encounter model (REM) was published. REM
is a camera-trapping method that derives animal density by using contact
ratio between camera-traps and targeted animals that randomly move at a
certain speed in a given area. However, it requires an independent value,
which is animal speed. For investigating animal speed, camera-traps with
video recording and GPS tagging are the commonly used tools. Unmanned
aerial vehicles (UAVs) are currently used in wildlife monitoring to
investigate the abundance of target species. It is evaluated as a tool
that is non-invasive and suitable for surveys in inaccessible landscapes.
Considering these characteristics, we regarded a distant survey using this
technology as suitable for investigating animal movements. Therefore, we
proposed a method for estimating animal movements using UAVs and conducted
a case study that aimed to investigate wild boars' movements. We
collected 11 video samples that successfully followed the movements of
wild boars from 26 UAV flights in total, and the average speed of their
movements derived from all the samples was 1.54 km/24 h. We found that
issues can be improved, including species identification, video sample
length, and animal behaviours or activity patterns. On the other hand, our
method showed potential for applying to species with specific
characteristics in their body size, shape or activity patterns. With
improvements in the issues mentioned above, UAVs would become an
alternative tool for investigating animal movements.