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Micryletta steinegeri Boulenger,1909 (史丹吉氏小雨蛙)

Scientific Name: Micryletta steinegeri Boulenger,1909
Common Name: Stejneger's narrow-mouthed toad
Chinese name: 史丹吉氏小雨蛙


Stejneger’s narrow-mouthed toad is endemic to Taiwan. Its distribution range is in low elevation areas. Its numbers are limited, as is its range, from central Taiwan southward including Taichung, Yunlin, Chiayi, Tainan and Kenting. Its northernmost boundary is Taiping District of Taichung City. Its habitats include broadleaf forest, bamboo groves, reclaimed land and orchards. It prefers areas of thick layers of dead leaf litter. Breeding season is in summer.

~~Morphological Characteristics~~
Adults: Stejneger's narrow-mouthed toad is a small-sized toad measuring around 2-3cm in length. On the otherwise smooth skin are warts of different sizes, of which those on the inside of the thighs and near the cloaca opening are larger. The snout is round and obtuse. The head length and head width are the same. The tympanum and temporal fold are indistinct. The dorsal color is brown or dark gray with stripes or dark brown spots. The mid-dorsal stripe is formed by tiny warts. The dorsolateral fold on the flanks is indistinct. There is a black line running from the snout to the flank.
The belly is smooth and grayish white with brown spots. The dorsal side of the forelimbs is light brown with dark brown spots. Fingertips are round, webless and without disk. There are three metacarpal tubercles. The dorsal side of the hindlimbs is covered with dark brown spots. The toes are webless with no disk at the tips. Well-developed inner metatarsal tubercles exist, but outer metatarsal tubercles do not.

Secondary sexual characteristics: Male has a single vocal sac under the throat and no androgenic gland.
Color: Brown and translucent along the belly; central line along tail muscle and the tip of the tail are lighter in color.
Body shape: 5.8~7.0mm (stage 34~36); oblong
Snout: Wide
Mouth: Snout tip
Labial tooth row formula (LTRF): Nil
Eyes: Lateral
Spiracles: Medioventral
Tail: Filiform at the tip

~~Taxonomic Studies~~


Boulenger, G.A.

Year of publication


Person credited with discovery

Mr. H. Sauter

Date of discovery



Boulenger, G.A. 1909. Description of Four new Frogs and a new Snake Discovered by Mr. H. Sauter in Formosa. Annals and Magazine of Natural History, Ser.8 6(24):492-496.

Type specimen classification


No. of specimens: Five specimens from Kanshirei

Scientific name changes




~~Ecology and Behavior~~
Stejneger's narrow-mouthed toad inhabits thick layers of dead leaf litter in broad-leaved forests, bamboo groves and orchards. It is a small-sized species with good protective coloration, making it hard to spot. Traces of this toad’s activity are more easily seen in the summer after a rainstorm. They breed in spring and summer and call for mates from places near small water holes after a rainstorm. Their calls are high-pitched and continuous, similar to insect calls. After mating, the female leaves behind sheets of eggs floating on the water surface. The female lays 200-300 eggs at one time. The eggs are contained in gelatinous coverings and only need one day to hatch into tadpoles, which are transparent and feed on plankton in the water.

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