The common bronzeback is a long, slender non-venomous snake that lives on trees. It shows adaptations in form and behaviour, allowing it to climb trees and leap across branches.
The common bronzeback (Tamil: komberi mookan), Dendrelaphis tristis, is a non-venomous tree snake that is commonly seen in the Indian subcontinent. This long and slender snake lives on trees across diverse habitats, ranging from forests to urban gardens. It belongs to a subfamily of tree-dwelling vine snakes (Ahaetuliinae) distributed from south and south-east Asia to Australia, which evolved about 30 million years ago. These snakes consist of two related groups – those with rectangular snouts and round pupils, such as the common bronzeback and flying snakes (genus Chrysopelea), and sharp-nosed snakes with horizontal pupils, such as the Indian vine snake (Ahaetulla oxyrhyncha, Tamil: pachai pambu), which is found in the plains of peninsular India.
The common bronzeback can grow up to four feet long, and has a brown body and a pale yellow underside, with a white spot on its head, a black streak behind its eye and a bronze stripe running along its spine. When excited or disturbed, it expands its neck and upper body to reveal bright blue colouration between its scales. It has acute eyesight and is active during the day, when it stays alert and is quick to flee. The common bronzeback lives among bushes and trees across habitats and lays eggs in tree holes, leaf litter, and nests of birds. Like other vine snakes, the common bronzeback feeds on frogs, garden lizards, geckos, and small rodents and birds. It is not scared of heights, and is known to jump between branches of trees and even drop several meters to the ground.
Tree-dwelling snakes show adaptations to their skeletal structure, with a large number of vertebrae in their tails, which help them climb and travel between trees. A longer tail may help a tree snake traverse gaps by acting as a counterweight, which prevents its body from slipping downwards as it reaches across the gap. Recent biomechanics studies show that these snakes extend their body in a straight line to bridge small gaps, while they use more dynamic movements to cross gap distances greater than half of their body length. They start from a lower vertical position and use faster looped jumps for these challenging crossings. Flying snakes in the genus Chrysopelea are aerial acrobats, which leap from branches and glide large distances by flattening and undulating their bodies to generate lift and gain speed.
On the IMSc campus, the common bronzeback has been seen among shrubs and trees on the hostel side of the campus, and spotted climbing up a cannonball tree in the lawn near the main building.
