When designing an animal pathway, ensuring the safety of humans and vehicles, as well as maintenance-free operation, is crucial. Additionally, considerations are given to factors such as cost reduction, safety for the animals using the pathway, and user-friendliness.

Consideration of Shape and Materials

Based on the results of model testing, it was determined that a suspension bridge-like structure consisting of a triangular frame, mesh flooring, and wires would be suitable. The material used needs to be sturdy to prevent it from rotting and causing accidents on the road, even though materials like branches and vines may be preferred by animals.

The proposed design from the company was examined and verified in collaboration with the Keep Yamane Museum. The museum conducted various experiments over the course of a year, involving the participation of captive Yamane to collect experimental data.

<Experimental Parameters >

  • Thickness and material of the wires
  • Coarseness of the mesh and width of the pathwa
  • Shape and material of the refuge points along the pathway

Discussions were held to address various issues and find solutions, such as minimizing snow accumulation on the pathway to reduce load and preventing icicles from falling onto the road. A prototype measuring approximately 10 meters in length was used to observe the effects of snow accumulation, and structural calculations considering snow and wind were performed for the Kiyosato No. 1 installation.

Consideration for Animal Ecology


To accommodate the preference of squirrels, who dislike confined spaces, and for maintenance-free purposes, an open design without large walls was deemed beneficial. However, precautions were necessary due to the increased risk of predation by raptors for Yamane and Hime-nezumi. As a countermeasure, refuge spaces covered with metal plates were placed at several locations along the pathway (indicated by the red boxes in the photo). Monitoring confirmed their utilization.

Refuge area installed for Yamane and Japanese Dormouse on the pathway floor.

Installation of Moving Ropes

Since Yamane often move by hanging upside down from tree branches in the forest, ropes for movement were installed near the triangular roof of the pathway. Small roofs were also attached to the top of the pathway to conceal the animals from their natural predators. Monitoring was conducted to observe the animals’ movement using the ropes.

Rope provided for Yamane movement on the upper part of the pathway.

Installation of Anti-Slip Measures

Thin cedar boards were wrapped around the support columns to provide better grip for the animals.

Cedar wood wrapped around the support column.

Guidance to the Pathway

To guide animals from the surrounding trees to the pathway, branches and ropes were extended from the trees to the pathway floor.

Guiding branches passed from surrounding trees to the pathway floor.

Tree species preferred by the animals were planted near the pathway’s support columns, and nest boxes were placed to encourage the animals’ use. The nest boxes have been confirmed to be used not only by Yamane and Hime-nezumi but also by wild birds.

Initially, artificial feeding was provided to inform the wildlife of the existence of the pathway. Feeding needs to be continued until regular utilization is observed.

Nest box installed at the edge of the pathway.

Importance of Entrance Pathways for Squirrels - Improvement Work

Experimental model for squirrels.

After two years since the installation of Kiyosato No. 1, frequent appearances of Yamane and Hime-nezumi were observed, but no usage by squirrels was confirmed. Although there were signs of squirrel activity near the pathway, the reason for their non-utilization remained unclear. To address this, several improvements were made:

The size of the triangular frame, which may have been too small for squirrels, was reconsidered. Several different-sized models were created based on input from researchers, and field experiments were conducted. As a result, squirrel utilization was confirmed regardless of the size.

One opinion suggested that the large size of the monitoring camera compared to the pathway may have been a cause for squirrels’ non-utilization. To address this, the camera position was changed, and the space in front of the entrance was opened up (the photo on the left shows the situation before improvement, and the photo on the right shows the situation after improvement).

Finally, attention was given to the introduction of squirrels from the surrounding trees into the pathway, and a new pathway that is easier for squirrels to cross was established. Considering durability and cost, resin-based angular pipes (called “Kaku-Flex”) used in electrical wiring were chosen as the material. When the branches of the trees were extended to the pathway floor using the Kaku-Flex pipes, squirrels appeared, and unexpectedly, the utilization of raccoons was also confirmed. This highlighted the importance of the entrance pathways, and the significance of this result was recognized.