Forest road use by mammals revealed by camera traps: a case study in northeastern Japan

We evaluated forest road use by mammals in forest areas in northeastern Japan using a camera-trapping survey, considering road surface conditions. From August to December 2021, camera-trapping surveys were conducted on paved forest roads, forest roads without understory vegetation, forest roads with low-height understory vegetation, forest roads with high understory vegetation (herbs and shrubs), and forest interiors. We analyzed the differences in forest road use by mammalian species using non-metric multidimensional scaling and a generalized linear mixed model. We also assessed whether each species actively used forest roads using the road-use index, which indicates that individual animals walked along forest roads based on consecutive photographs. The paved forest roads and unpaved forest roads with no or low-height understory vegetation had a similar composition of species using the roads. The unpaved forest road with high-height understory vegetation showed a species composition similar to that in the forest interior; however, the results were different from those of the other three groups. Except for Japanese squirrels, mammals had little tendency to avoid forest roads and also indicated the existence of species (i.e., medium-sized carnivores) selectively using forest roads in the study area. Our results suggest that understory vegetation height on the forest road surface influences species composition through its effect on medium-sized carnivores and Japanese squirrels. This study provides useful knowledge on the relationship between human activities and wildlife, particularly in forest and wildlife management.