Mortality of Monarch Butterflies (Danaus plexippus) at Two Highway Crossing “Hotspots” During Autumn Migration in Northeast Mexico

摘要: The contribution to annual mortality of migrating monarch butterflies (Danaus plexippus) due collisions with vehicles is poorly understood but likely significant. Recent estimates based on a study in Texas suggests that during autumn migration may be the order 2 million per year or about 3% population. However, MaxEnt models used are not well suited quantifying at hotspots where monarchs concentrated by topography such as canyons when crossing highways. Potentially catastrophic could occur sites if timing and weather conditions conspire force large proportion population across highways low altitude. We investigated 15 October 11 November, 2018 two highway crossings northeastern Mexico known for their frequent extensive (La Muralla Santa Catarina). During 15-19 day period migration, we collected dead injured along series 500 m roadside transects. estimated minimum total fall just these 196,560 individuals. Monarchs exhibited diurnal pattern passage Catarina peaks late morning afternoon. Average vehicle speeds exceeded posted 60 km/h limits designed protect monarchs, ranging from 75.1 99.6 La 86.6 106.8 Catarina. recommend finer-scale documentation pathways an inventory significant northeast Mexico. Mitigative measures include better enforced least short deflection structures raise height and/or manipulation habitat lower potential descending roost near key points.