Effects of multiple targeted repelling measures on the behaviour of individually tracked birds in an area of increasing human-wildlife conflict.
Some animal populations are rapidly increasing in numbers and expanding their ranges, leading to intensified human-wildlife conflicts. A wide range of tools has been developed to repel animals from areas where they are suspected to cause damage. For waterfowl, direct comparisons of multiple repelling methods have so far focused only on species' presence, total numbers, cost effectiveness or subsequent damage assessments, but not on individual behaviour. Here, we investigated the individual responses of free-flying geese to three repelling methods using high-resolution tracking data. In an experimental setup, tracked individuals were repelled by human approach, gunshot sound or handheld lasers. We found that repelling success and return time to the field where the repelling took place increased when individuals were repelled multiple times. Travel distances after the repelling events were longer after human approach and gunshot sound compared to the handheld laser treatments. In spring, the probability to return to the same field was higher after repelling with handheld lasers, but no difference between treatments was evident in autumn. We observed no increase in the probability to visit accommodation fields, where geese were allowed to forage and were not repelled, after the repelling events. Synthesis and applications. We found no strong differences between the three methods regarding the repelling effectiveness and the resulting behaviour of the tracked geese. However, the higher return rates of individuals after repelling with handheld lasers in spring suggest that this method might be less effective in situations with bright sunlight or very large aggregations of geese. Apart from these limitations, we can recommend handheld lasers for repelling as they might reduce energetic losses for the geese and disturbance of non-target wildlife. Since repelling by gunshot sound and handheld lasers was twice as fast as repelling by human approach, those methods will reduce working hours by 50% and therefore be more cost-effective in practice.