Brown tree frog
Length: SVL: Males up to 37mm; Females up to 49mm
A small brown frog introduced from Tasmania in 1875, the brown tree or whistling frog is now widespread in the southern North Island and through the South Island. It is important that frogs which are held in captivity are not released into the wild as they may pose a threat to our native frogs through transmission of disease and competition. The brown tree frog can be distinguished from native species by their loud vocalisation (native frogs are essentially silent).
The ventral (lower) surface is a creamy white, with breeding males possessing a dark brown throat. The armpits and groin have varying amounts of light yellow or green. The thighs may sport vivid orange markings and this is especially common in mature females. The snout is truncated when viewed in the lateral profile. Eardrums are quite distinctive and can be used to distinguish the brown tree frog from native frogs (which do not have an obvious external eardrum).
Brown tree frog are sexually dimorphic with females being larger than males (female SVL <50mm, male SVL <40mm). Tadpoles reach up to 50mm in length and are typically very dark with a blue or olive tint with a metallic belly.
High pitched and cricket like, a series of 5 or 6 trills of which the first sound is prolonged. Males call year round, particularly after periods of rain.
Widespread in the South Island as well as the central and southern parts of the North Island.
Ecology and habitat
Found across a wide range of habitats including farmland, forests, and suburban areas, as well as semi arid and alpine areas.
Brown tree frog are unique in that they can breed throughout the year. Breeding takes place in fresh or mild brackish water from the coastal to alpine zones. Fertilisation is external with eggs laid in clumps attached to submerged plant stems and aquatic vegetation. Tadpoles are black when first hatched, turning brown as they mature.
Gill, B.J., & Whitaker, A.H. (2007). New Zealand frogs and reptiles. Auckland: David Bateman Limited.
Jewell, T. (2011). A photographic guide to reptiles and amphibians of New Zealand. Auckland: New Holland Publishers.