Water Monitor Lizard (Varanus salvator)

I was trying to photograph some egrets that were sitting in a dead tree next to a pond when I observed this monitor lizard steadily making its way up the tree. Until then I was not aware that they could climb trees! This one was at least 15-20ft off the ground. On land I have observed them run pretty fast over short distances although they are in their element in water. When I finally left the area it was still sitting up the tree. It would have been at least 3-4ft long. The birds didn't seem too bothered .. they just moved higher up.