Comparison of Climbing Ability of Vertical Wall between Two Closely Related Colubrid Snakes

On the main islands of Japan, two closely related colubrid snake species, the Japanese rat snake (Elaphe climacophora) and the Japanese striped snake (E. quadrivirgata), coexist in sympatry. These species differ in habitat utilization: E. climacophora is semi-arboreal, while E. quadrivirgata is mostly terrestrial. Due to the differences in habitat utilization of the two species, I hypothesized that E. climacophora would exhibit superior climbing ability to E. quadrivirgata. To test this, I conducted two behavioral experiments in captivity. In Experiment 1, I compared the climbing speed of adult individuals of both species on a vertical surface formed by a 45-degree intersection of a plywood board and a wall. In Experiment 2, I tested whether hatchlings of the two species were able to climb a 90-degree corner formed by two intersecting walls. The results showed that, in adults, the hypothesis that E. climacophora climbs faster than E. quadrivirgata, independent of size differences, was only partially supported, while in juveniles, E. climacophora exhibited significantly higher climbing success rates than E. quadrivirgata. Overall, these findings suggest that E. climacophora possesses superior climbing ability across life stages. As a future direction, I briefly discussed a potential link between differences in climbing ability and differing patterns of avian prey exploitation.