A blue poison dart frog rests atop an emerald tree boa as it nestles on a tree branch. Both are native to South America. Mixed species exhibits like this one are part of RepTopia - Singapore Zoo's newest exhibit - which opens this weekend. Such inter-species interaction is not only enriching for its inhabitants, but also elevates the viewing experience for visitors. RepTopia features some 60 species of reptiles, of which about a third are threatened, and are held in the park as assurance colonies in case they go extinct in the wild.