Masked palm civets (Paguma larvata) climb vertical crevice: widths of gaps that they could climb and changes in climbing method

Invasion of buildings by masked palm civets is a problem, and some measures to prevent it are needed. Masked palm civets often use arboreal habitats because they are good climbers, and they may use the insides of hollow walls as a path to enter attics in houses. The Japanese house generally has a characteristic dual wall structure comprising the outer wall and the internal partition, and the width of gap between them varies. These characteristics of a wall may affect the success or failure of the invasion of attics by civets. In this study, we used an experimental apparatus consisting of two flat boards with a vertical gap between them, and investigated the width of the gap that civets could climb. Three civets showed four types of climbing methods. They climbed basically vertical gaps between 6 cm and 25 cm in width by pushing the boards with their back and four limbs as the standard method. At widths of over 11 cm, it became difficult for civets to support their weight in a gap, when they were unable to climb a gap by the standard method, they tried climbing another place in the experimental apparatus, changed their posture, or their behavior when beginning to climb. The latency to start climbing and time to reach the reward increased below the 9 cm gap width and above the 17 cm gap width, meaning that a civet could climb a 9- to 17-cm wide vertical gap comparatively easily. The gap in a wall of most Japanese-style houses is around 8 cm to 11 cm. Therefore, masked palm civets could use a vertical gap in the walls of a house as a migratory pathway, and move freely inside buildings.