Brown Tree Snake

Boiga irregularis

Brown Tree Snake (Boiga irregularis) Brown Tree Snake, Boiga irregularis, note the large eye with a vertical pupil.


The Brown Tree Snake has a large head with eyes that are large and protruding with vertical pupils.  The head is distinct from the narrow neck.  They are brown above with ragged-edged, darker cross bands on the back and sides (eastern Australia).  Northern Australian specimens are cream with bold reddish bands.  The belly is cream to orange.  This snake grows to 2 m.  Midbody scale rows 19–23, ventrals 225–265; anal single; subcaudals divided 85–130.

Boiga irregularis distribution


Found in coastal and sub-coastal northern and eastern Australia, south to Sydney region.


A common species that lives in a  broad range of habitats including open forests, rainforests, mangroves, rock escarpments, rural and urban areas.


This snake is active by night and is, as the name suggests, arboreal.  It is often found coiled up in buildings, tree hollows and caves.


Australian Brown Tree Snakes are not generally considered dangerous.  However, recent  studies may indicate a need to re-evaluate this species' medical significance.  Bites in Guam  have produced severe symptoms with patients receiving ventilation or intubation to assist  breathing.  Such cases involve small children and large snakes.  The venom has myotoxic and neurotoxic components.  Apply first aid and seek urgent medical attention for all suspected bites.  First aid procedure for any snakebite from the Australian Venom Research Unit.


Feeds mainly on birds and their eggs but reptiles, frogs and mammals are also taken.


3-11 eggs are laid.  The hatchling snakes are around 30 cm from the tip of the snout to the base of the tail (snout-vent length).

Similar species:


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