Fruitful outcomes without fatal costs: non-lethal alternatives show promise in alleviating human-wildlife conflict involving an island flying fox

Human-wildlife conflict is a growing threat to biodiversity, primarily involving damage to agricultural production. In Mauritius, the threatened Mascarene endemic Mauritian flying fox (<i>Pteropus niger</i>) has been subjected to five annual mass-culling campaigns since 2015, which failed their crop protection goals while raising the species' extinction risk. We evaluated seven non-lethal potential deterrent methods to mitigate flying fox as well as bird damage to ripening fruits in lychee orchards. This study was conducted in close collaboration with local small- and large-scale fruit growers, who occasionally influenced the number and spatial arrangement of trees assigned to treatments and controls. We estimated expected fruit yield per tree before ripening, collected fallen fruits weekly over the four-week fruiting season and categorized them by damage agent. At five control sites, flying foxes damaged 0-88% (mean = 43%) of fruits on unprotected lychee trees. Two sites likely experienced high nocturnal human disturbance, which may have skewed flying fox damage on the control trees; excluding these sites, damage averaged 66%. The lowest flying fox damage occurred when trees were covered by netting or parallel cords (<1%), followed by a nocturnal sound-light system (4%), a nocturnal sprinkler system (11%), local traditional nocturnal smoke and lights (19%), flags positioned above the trees (25%) and flags saturated with repellent odours and placed above the trees (38%). Bird damage was less than that from flying foxes (1-12%, mean = 6%) and similar in most treatments, including netting due to holes in the nets. Testing the sound-light system in one mango orchard resulted in a reduction of flying fox damage from 60% to 20%, but an increase in bird damage from 1% to 16%. Overall, we provide evidence that various non-lethal crop protection methods are effective, although to varying degrees. In comparison, mass-culling campaigns failed to improve overall fruit production. In addition to the benefits of netting, which can carry relatively high upfront costs, this study highlights the potential value of the sound-light and sprinkler systems.