Moonlight-related mortality: lunar conditions and roadkill occurrence in the Amami Woodcock Scolopax mira

Roadkill is one of the most striking ecological problems related to roads and traffic. The Amami Woodcock, Scolopax mira, an endemic and endangered species on the islands of southwestern Japan, ventures out on roads at night, making it susceptible to becoming roadkill. In the present study, I investigated woodcock behavior on roads at night, trends in nighttime traffic at roadkill hotspots, and dates when roadkill occurred in the past on Amami-Oshima Island in southwestern Japan, to develop mitigation measures to prevent roadkill in this species. Woodcocks were abundant on roads when the moon was waxing; ∼90% of nighttime traffic was recorded between dusk and midnight. These findings were consistent with the occurrence pattern of roadkill in the past, that is, roadkills occurred frequently during the first half of the synodic month when the waxing moon crosses the meridian from dusk until midnight. This pattern was obvious particularly in the breeding season (Feb–May). As a mitigation measure, drivers should be asked to reduce their vehicle speed on moonlit nights, particularly several days before the full moon in March, because this is the most vulnerable period for the Amami Woodcock. The present study revealed that the interplay of three factors (woodcock behavior, trends in nighttime driving, and lunar conditions) accounts for the seasonal, periodic, and temporal patterns of roadkill specific to this species. Because night activities of various animals are affected by phases of the moon, lunar conditions may have stronger effects on roadkill in a wider variety of animals than has been previously recognized. Taking lunar conditions into consideration would be important for better understanding of roadkill patterns in a wide variety of animals using roads at night.