Southern Brown Tree Frog

Fascinating facts about the Southern Brown Tree Frog

• This frog reaches 45 mm (1.8 in) in length and has orange thighs.
• First described in 1841 by French naturalists Duméril and Bibron, the species now serves as a textbook case of reinforcement-driven speciation, where mating preferences sharpen to keep it distinct from its close cousin, the whistling tree frog. This illustrates evolution in action, tightening the species’ genetic boundaries.
• Since being introduced in Greymouth, New Zealand in 1875, the frog has become established in the North Island, South Island and Chatham Islands.
• Males make a whistling “weep-weep-weep” call from the edges of ponds, ditches and dam impoundments all year round, especially after rain.
• When winter temperatures plunge, these frogs can survive freezing solid, a physiological feat that likely costs them energy but lets them endure harsh alpine and semi-arid zones. Their freeze tolerance expands the range of habitats where amphibians can persist.

At a glance

About the Southern Brown Tree Frog

The southern brown tree frog, Litoria ewingii, is a modest-sized arboreal amphibian that reaches about 45 mm (1.8 in) in length. Its dorsal skin varies from pale to dark brown, often marked by a broad darker patch that begins at the eyes and spreads across the back, while a distinctive dark band runs from the nostril across the eye and tympanum to the shoulder, edged below by a pale white stripe that trails from the mouth to the arm. Though brown dominates, pure green and green-striped morphs appear frequently, especially in western Victoria and southeastern South Australia, and the backs of the thighs flash orange, a vivid contrast to the cream-coloured belly. These frogs inhabit an astonishing range of environments, from forests and heathland to farmland, alpine zones and suburban gardens, making them a familiar sight on window panes in Adelaide, Melbourne and Hobart, where they hover at night to catch swarming insects. Males announce their presence year-round with a plaintive whistling “weep-weep-weep,” emitted from the water’s edge or while floating on dam impoundments, ditches, ponds and stream-side pools; after rain the chorus intensifies, and the females lay eggs that wrap around submerged grass stems, aquatic vegetation and sticks. A remarkable, almost surreal trait is their ability to survive freezing temperatures, a physiological feat that likely incurs a hidden cost but enables them to endure the frosty nights of southern Australia’s alpine and semiarid habitats, pushing the boundaries of what we consider possible for a small ectotherm.

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