The total length of roads in Japan is approximately 1.2 million kilometers, equivalent to circling the Earth about 30 times. The length of railway tracks is about 27,000 kilometers. These continuous structures actually cause fragmentation in various natural and artificial environments. Particularly, roads and railways passing through forested and mountainous areas often lead to forest fragmentation, and mitigation measures are planned in the order of avoidance, reduction, and compensation. Replacement is considered as the final resort.

For existing roads and railways that have already caused forest fragmentation, there are limited options besides taking alternative measures, and mammals are suffering from the impacts such as roadkill. Underpasses, such as box culverts, have been constructed for animals like raccoons and deer, and their usage has been confirmed.

However, for arboreal animals that rely on overlapping tree branches for movement, there are currently very few alternative solutions available. The current situation is that despite records of roadkill incidents, little attention is given to addressing the issue.

Forest fragmentation leads to a decrease in opportunities for feeding and breeding, which in turn contributes to the decline and extinction of valuable species in the region. Additionally, even within the same species, the loss of genetic diversity can lead to genetic deterioration. Therefore, animal pathways that allow arboreal animals to safely cross roads and railways and utilize fragmented forests as an integrated habitat are essential.