A venomous snake (family Colubridae) found in sub-Saharan Africa that reaches 100–160 cm in length and in which males are mainly green with black or blue edges to their scales, and females are often brown. The snakes are diurnal, spend almost all their time in trees (the name means ‘tree snake’), and feed on eggs and small vertebrates. They are reclusive and bites are rare, but can be fatal to humans.