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Text and photos by Nick Baker, unless credited to others.
Copyright ゥ Ecology Asia 2024







Bornean Horned Lizard

Family : Agamidae
Species : Harpesaurus borneensis
Size (snout to vent) : up to 5.9 cm
Size (total length) : up to ~ 16 cm

Horned lizards of the genus Harpesaurus are endemic to insular Southeast Asia. As of 2021, Reptile Database lists 6 species of which 3 are endemic to Sumatra, 1 is endemic to the island of Nias in the Mentawai Islands off the west coast of Sumatra, 1 is endemic to Borneo, and 1 to Java.

These are small, slow-moving and highly elusive lizards. They are forest-dwelling, arboreal and mainly diurnal in habits. Unusually they are viviparous, which means that live young are born, unlike most other lizards which lay eggs.

Harpesaurus borneensis (Bornean Horned Lizard) inhabits lowland rainforest; adults are typically encountered on vegetation between 1.5 and 6 metres from the ground. The slow, deliberate movements of this curious lizard have been described as chameleon-like, with a waggling motion (Lardner et al, 2010).

Its body is slender, laterally compressed, and its legs spindly. Its tail is long, slender and rather stiff; this curves upwards when the lizard is stressed (see Figure 2).

Males possess a small, straight 'horn' on the rostrum; in females the presence or absence of a horn appears variable. (In other species, for example Harpesaurus beccarii and Harpesaurus brooksi both from Sumatra, the horn is thicker and more curved. And some species may bear 2 horns, for example Harpesaurus tricinctus from Java.)

In Harpesaurus borneensis a weakly developed crest is typically present on the back of the neck, and males also have a low crest along the back and on the tail.

When undisturbed the colour of Harpesaurus borneensis is described as "dull olive green with brown diagonal markings" (Lardner et al, 2010). When disturbed or stressed its overall colour changes to reddish brown. There are oblique rows of small, dark spots and faint pale brown banding on the body, and the tail bears dark and pale bands.

The diet of some Harpesaurus lizards is known to comprise a variety of insects and other arthropods.

Figs 1 and 2 : Female found on a slender branch around 3 metres from the ground. Its original colour was greenish, however it became brownish when disturbed. This example bears a slender, but well developed horn. Whilst being photographed this female gave birth to two juveniles (see example in Figure 3).

Fig 3 : Newly-born juvenile, offspring of the female in Figures 1 and 2. 

All photos taken in primary hill dipterocarp forest (away from any stream) at Kubah National Park, Sarawak, Borneo. Thanks to Law Ingg Thong.

References :

Bjrn Lardner, Sing Yun Chin and Ulrich Manthey. (2010). Notes on Harpesaurus borneensis (Mertens, 1924), a live bearing agamid lizard from the lowlands of Borneo. Russian Journal of Herpetology, 17(3), 231-235.

Links :

Reptile Database


Fig 1
ゥ Law Ingg Thong
Fig 2  
ゥ Law Ingg Thong
Fig 3  

ゥ Law Ingg Thong