Amidst nets and typhoons: conservation implications of bat-farmer conflicts on Okinawa Island

Abstract

Flying foxes are keystone species on islands and are threatened worldwide, particularly by forest degradation, hunting and culling. They are often persecuted if they are perceived as agricultural pests, but the extent of crop damage from flying foxes and the factors triggering their visits to crops are not well established. This study aimed to investigate wildlife-caused damage to tankan oranges Citrus tankan on Okinawa Island, Japan, and interactions between the Ryukyu flying fox Pteropus dasymallus and farmers. We compiled data from three sources: official records of wildlife-caused crop damage, questionnaire surveys of 43 farmers and time-lapse camera surveys conducted at 14 locations during January-February 2018. Official records and the questionnaire survey indicated that the large-billed crow Corvus macrorhynchos caused most damage in a typical year (53-56% of the total damage), followed by P. dasymallus (18-28%). However, time-lapse camera surveys suggested negligible damage caused by P. dasymallus (2.1%) in 2018, a typhoon-free year. Farmers perceived a decline in local population size and stated that at least 2,000 P. dasymallus individuals had died in their orchards during 2008-2018. If this is extrapolated to the whole region, fatalities could have reached 6,500-8,500 individuals during that period. Binomial regression performed on official records demonstrated that damage by P. dasymallus was largely explained by interannual cyclonic activity. Prevalent netting practices could be a serious threat to P. dasymallus: 81% of interviewees reported that flying foxes die from entanglement in their nets. Nevertheless, half of these farmers were satisfied with current crop protection measures. These findings call for prompt remediation with particular focus on implementing more bat-friendly crop protection following strong typhoon seasons.