Do substrate type and gap distance impact gap-bridging strategies in arboreal chameleons?

Chameleons are well-equipped for an arboreal lifestyle, having zygodactylous hands and feet as well as a fully prehensile tail. However, to what degree tail use is preferred over autopod prehension has not been studied to date. Using an experimental set-up, where chameleons had to cross gaps of varying distances, we tested the effect of substrate diameter and type on tail use in Chamaeleo calyptratus. Our results show that when crossing greater distances, C. calyptratus is more likely to use its tail for additional stability. The animals were able to cross greater distances (up to 1.75 times the shoulder-hip length) on perches with a rougher material. We saw that depending on the distance of the gap, chameleons would change their crossing strategy on how they use their prehensile tails. With shorter gaps the tails either do not or only touch the perch without coiling around it. With larger distances the tails are fully coiled, and with the largest distances the tails are fully coiled around the perch and after repositioning the hind legs, shifted towards the end of the perch. Males were able to cross relatively greater distances than females, likely due to their larger size and strength. Summary statementChameleons use their prehensile tail more often when crossing greater distances and switch strategies on when and how they use their tails. Males are able to cross relatively greater distances than females.