Description Leptobrachium montanum is a stocky frog with a broad head and snout-vent length in females of about 87 mm and in males about 65 mm. The snout comes to a rounded tip, with a slight fold from the nostrils to the upper lip. It has large eyes and a fairly large canthus. The pupil is small and vertical, with the longitudinal diameter of the upper eyelid equal to the interorbital space. There is a glandular fold from the base of the eye to the ear. The nostrils are close in proximity and inconspicuous. It has a large, almost circular shaped tongue. The forelimbs are skinny and longer in relation to the hind legs. The second finger is slightly thickened towards the tip and is longer than the first. The back has a small indentation. The dorsal and ventral skin has a smooth texture (Fischer 1885).
Leptobrachium montanum is morphologically similar to Leptobrachium gunungensis. Both frogs belong to the family Megophryidae and are considered sibling species. These two species can be distinguished slightly by distribution and more notably by their distinct calls (see Life History section; Malkmus 1996).
The dorsal surfaces are brown and appear to be reticulated. There are black-fringed round spots irregularly scattered on the dorsum. The limbs may have black bands and white or pale yellow dot-like spots. The belly is lighter than the dorsum, and may be grayish with bright yellow dots concentrated in the chin and throat area. Outside the iris, the eye sclera is white (Fisher 1885).
The tadpoles have a strong tail with a well-developed caudal fin. The snout of the tadpoles is long and blunt. The tail is patterned with dark spots. As the tadpole ages and develops, the number of dark spots on the tail increases until the body color is darker in general (Nodzenski et al. 1989).
This species is endemic to Borneo. It can be found within the countries of Indonesia and Malaysia. It is primarily found within the states of Sabah and Sarawak. It has an altitudinal range of 900 m up to 1800 m where these frogs live in tropical montane and submontane forests. They are able to withstand the cooler nighttime temperatures (Inger and Tan 1996).
Life History, Abundance, Activity, and Special Behaviors Leptobrachium montanum is abundant in numerous localities (Inger et al. 2004). When feeling threatened, the frogs will crouch within leaf litter and mimic dead leaves (Manthey and Grossmann 1997).
The advertisement call of L. montanum is a loud ‘quak’, which sounds similar to a duck quack (Fischer 1885). The species breeds in small streams of montane forests where the larvae develop within small pools of breeding streams (Inger et al. 2004). The tadpoles are large with bulky bodies (>70 mm) and are more active during the night, although they can be seen during the day (Nodzenski et al. 1989).