This is a long and slender snake with adults reaching lengths of 1,5 – 1,8 m but they can reach up to 2,4 m. The head is coffin-shaped and slightly distinct from it’s neck. The eye is medium sized with a round pupil that is narrowly edged with bright ochre to golden-yellow and an iris that is yellow-brown to olive-green. Inside of the mouth is pink to light bluish-white, but never black like the Black Mamba’s mouth, except hatchling Green Mambas that may have black inside the bottom of the mouth which fades and becomes pink as the snake grows. The snake’s colour is bright emerald-green to grass-green, or lighter green and they may have individual yellow scales. The belly is paler. The dorsal scales are smooth and dull in 17 – 21 oblique rows at mid-body. Their subcaudal scales are paired and the anal shield is divided.
Fixed front fangs on elongated maxillary bones.
They have a fast-acting neurotoxin that causes a progressive weakness syndrome (PWS), paralyzing the lungs leading to death. The cytotoxin from a full bite causes considerable swelling of the bitten area, without bite-site necrosis. An adult’s lethal dose is 15 – 20 mg and the snake’s venom yield is 40 – 80 mg. They do not bite as readily as a Black Mamba. Majority of bites from this snake is mild with a small volume of venom injected, but victims should receive medical care as soon as possible. Polyvalent anti-venom is available to neutralize the venom.
They occur in densely forested, low-lying areas. In Southern African they are restricted to the coastal forest. They use tree-hollows or dense creepers as cover.
They are diurnal and mainly arboreal and are seldom found outside forests or dense bush. The Green Mamba emerges early in the morning to bask before foraging for birds and their nestlings, squirrels or other rodents. They return to their refuge in the late afternoon. This snake will often live in close proximity to humans, seeking refuge in ceilings where it will remain and forage from for many years if not disturbed. They are often confused with Boomslang or Green Snakes of the genus Philothamnus.
Owing to their arboreal habit and placid nature, very few bite-records exist, and the majority of bites are incurred by snake catchers and keepers when their hands are mistakenly bitten during a feeding response, or during rough handling. They do not usually gape the mouth or flatten the neck like a Black Mamba, but will vent it’s displeasure by emitting hollow-sounding hisses.
They reproduce by laying eggs in spring.