Individual responses of GPS-tagged geese scared off crops by drones or walking humans.
Abstract
Scaring of wildlife is commonly used in attempts to reduce crop damage in agricultural landscapes, but relatively few studies exist on its actual effect. We tracked GPS-tagged greylag geese (Anser anser) in south-central Sweden, before and after scaring by approaching them either by walking or by drone. On the field level, we studied the scaring effect by estimating return rate to the field where scared. On the landscape level, we tested if geese were less prone to use agricultural fields after being scared. Geese immediately left the field when scared and 5 min later they were on average 990 m (±56 SE) from the scaring position. The proportion of GPS positions near the scaring position decreased significantly for at least 4 h after scaring. Geese showed a significant shift from agricultural fields to wetland habitats the first 4 h after scaring. However, the effect of scaring soon levelled off; after 24 h the field where scaring had occurred was used to the same extent as any other field in the landscape, and agricultural fields were used to the same extent by scared and undisturbed geese. We did not find any differences in response depending on scaring technique. The probability to return and use agricultural fields after scaring was higher for geese scared in the morning compared to in the afternoon. Moreover, the probability to return and use of agricultural fields were higher in spring than in other seasons. Practical implication. We found that scared geese tend to visit agricultural fields soon after scaring and that scaring alone tends 'to move the problem around'. This suggests that scaring needs to be repeated across the landscape, but also that accommodation fields where geese do not cause damage may be needed to keep geese off conventional fields. However, our study presents a glimpse of promise as the rather simple drone used covers large areas quickly and minimizes walking in growing crops. With technological advancement and possible autonomous techniques, drones may be capable of providing repeated scaring over large areas in the future.