True toads (family Bufonidae) form a cosmopolitan group of amphibians best known for their characteristically dry, warty skin and the prominent parotoid glands behind the eyes, which secrete a milky toxin as a defense mechanism. In many languages, the word “toad” is commonly applied to any warty, stout-bodied frog. Scientifically, however, Bufonidae refers only to true toads—a taxonomic group defined by a unique set of shared derived anatomical features.

On the island of Borneo, true toads occupy a wide range of habitats, from lowland rainforests to montane regions. More than 30 species are currently recognized from Borneo, and additional species are likely to be discovered. Particularly notable is the radiation of stream toads (Ansonia), which are specialized for life in Borneo’s forest stream systems.

Although many Bornean bufonids are associated with lowland habitats, several species extend into the highlands. Ansonia fuliginea holds the record for the highest elevational distribution of any Bornean frog, occurring above 3,000 m a.s.l. on Gunung Kinabalu, Sabah.