One early afternoon I was due to meet my guide Udaya Chanaka for a trip to a nearby national park. I was a few minutes early so I meandered about the grounds of the tented camp in which we were staying. My eye caught a snake-like shape about head-high in a nearby tree, but the snake-like shape's eye must have caught me at the same time, because it held still for approximately two seconds and then turned tail and zipped upwards into the tree for approximately three seconds before I had completely lost sight of it. I recognized it as a Dendrelaphis and Chanaka ID'ed it as D. tristis based on our location and my brief description.