Common tree snake

Identification

The common tree snake is an agile, extremely slender snake with a whip-like tail^1,2. Its colour varies from place to place: it may be grey, olive-green, various shades of brown, almost black or even blue above, and lighter snakes often have a grey or brown head that contrasts with the body². The belly is usually lemon-yellow, but it can be white, olive, green or bluish². It has large eyes and keen eyesight⁶. Besides “green tree snake”, it is sometimes called the yellow-bellied black snake³.

Adults average about 1.2 m long, and the largest reach 2 m².

Distribution

The common tree snake lives in northern and eastern Australia and in Papua New Guinea^1,4. Its range runs from the Kimberley region of Western Australia through the Northern Territory to Cape York and the Torres Strait, and then down the east coast into New South Wales^1,4. In Queensland it is widespread along the east coast and on Cape York Peninsula, and it is common throughout Brisbane^1,2. A form once treated as a subspecies, Dendrelaphis striolatus, is now regarded as a separate species⁴.

Habitat

This snake uses a wide variety of habitats, from woodland and rainforest to tropical gardens¹. In Queensland it lives in coastal forest, rainforest, wet and dry eucalypt forest and riverside vegetation, and it is usually seen in eucalypt woodland or rainforest^2,3. In New South Wales it is found in rainforest, open forest and rural areas, as well as in suburban gardens⁶. It is often seen in trees, gardens and on verandahs, and sometimes even enters houses¹.

Behaviour

The common tree snake is active by day, spending most of its life in trees and shrubs but also hunting on the ground^1,2. At night it usually sleeps in tree hollows, crevices or foliage¹. In a seven-year study of 131 snakes from a dark-coloured population near Townsville, activity peaked during the breeding season, at the change from the dry season to the wet season⁵. When it meets people it usually retreats quickly². If threatened, it raises itself and inflates its body to show splashes of blue skin between its scales, and it often gives off an unpleasant smell^1,2,3.

Diet

The common tree snake feeds mostly on frogs and skinks¹. Other recorded prey includes birds, other reptiles, fish and occasionally small mammals^2,6. Snakes studied near Townsville ate frogs, lizards and locusts⁵. It actively hunts frogs by day and is often seen around houses and gardens where frogs live².

Reproduction

The common tree snake lays eggs⁴. Females lay clutches of 4–16 long, narrow eggs¹. Near Townsville, breeding was strongly seasonal, and larger females laid larger clutches⁵. In the same study, females were larger than males in every measurement, including weight and head size⁵.

Venom and medical significance

The common tree snake has no fangs and no venom^2,6. It is harmless to people, is not aggressive, and bites only as a last resort^2,6. Its main risk is mistaken identity, because it is sometimes taken for a venomous black snake². If there is any doubt about which snake caused a bite, seek medical care.

Conservation

The common tree snake is listed as Least Concern on the IUCN Red List (assessment published in 2018)⁷. It is also listed as Least Concern in Queensland under the Nature Conservation Act 1992¹. It remains common and widespread, including in suburban Brisbane¹. Sadly, tree snakes are sometimes killed when people mistake them for venomous black snakes².

Similar species

Common tree snakes, which can be almost black, are sometimes killed when mistaken for venomous black snakes². The dangerous red-bellied black snake (Pseudechis porphyriacus) is glossy black with bright red or pink scales along the edge of its belly, whereas the tree snake is far more slender, with a whip-like tail, large eyes and usually a lemon-yellow belly^2,3. On eastern Cape York, the related northern tree snake (Dendrelaphis calligastra) is smaller, averaging 0.8 m and reaching 1.2 m². The brown tree snake (Boiga irregularis) is rear-fanged and weakly venomous; it is active at night and has a broad head, large eyes and dark cross-bands on a brown to reddish body². These differences are not a safe basis for handling any snake. Keep your distance from every snake you cannot identify.

In captivity

In Queensland, all wildlife, including this snake, is protected under the Nature Conservation Act 1992, and it is an offence to keep a snake taken from the wild². Anyone who wants to keep a snake there can legally buy a captive-bred animal from an authorised reptile dealer, and must also hold a wildlife licence². Tree snakes often visit gardens and verandahs to hunt frogs, and they usually retreat quickly from people^1,2.