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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 :
Björn 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
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