Order: Squamata - Lizards and Snakes
Phylum: Chordata - Vertebrates
Red List status: Not listed
Snout-vent length 284 mm 284 mm
Total length 685 mm 400 mm
Endemic to Madagascar, where it is the most widespread chameleon species. It has been recorded from all parts of the island in a variety of dry and moist sites at all elevations.A localised population introduced to Kenya is probably extinct.
Regarded as the world's longest chameleon (although exceptionally, longer adults of Calumma parsonii have been reported). This species reaches lengths approaching 70 cm (over 2 ft), and is also the second heaviest member of the family (after Parson's chameleon). However, many specimens encountered are likely to be smaller adults or subadults. The casque is high, with a pronounced parietal crest. Rostral crests are present and extend to the snout tip, but do not connect. A lateral crest is present but
The most important diagnostic characteristic is the dorsal crest, which extends to the vent and consists of 45 or more short, triangular spines with regular spacing between them. Ventral and gular crests are present, but are unconnected to one another.
Colouration in both sexes is often grey or brown, although females are typically more colourful and may exhibit red colouring on the head and limbs. However, females can be variable with yellow colouration or mottling, and may in some cases be largely green. Patterning may include a row of four large, dark-edged circles along the flanks, although a white line is absent in contrast to F. lateralis. Indistinct dark vertical bands are often present on the flanks. The absence of a white mid-ventral stripe is regarded as diagnostic, but see the caveat in Taxonomy below.
Similar species: The only species with which full-sized adults may potentially be confused are the other two large chameleon species, the closely-related Furcifer verrucosus and the distantly-related Calumma parsonii (Parson's chameleon). The latter is very easily distinguished, as this species is more colourful, is restricted to rainforests where F. oustaleti is scarce, has a heavier build, and in the male possesses two rostral appendages where Oustalet's chameleon has none. This species also lacks parietal and gular crests, and the back of the head is distinctly triangular in profile (as opposed to rounded in F. oustaleti).
Oustalet's chameleon can be distinguished from F. verrucosus most readily by its dorsal crest, which in the latter species consists of fewer than 40 long spines extending along the length of the body (in males), or short spines at the front of the body only (in females). Confusion may also potentially arise between subadult F. oustaleti and F. nicosai, a related dull-coloured Furcifer species without a rostral appendage. Green morphs can potentially be confused with with F. lateralis, from which it can be distinguished by the presence of a spined dorsal crest distinguishes and the usual absence of a mid-ventral stripe in Oustalet's chameleon. The recently-described F. nicosiai has a dorsal crest of 50-60 short spines in males; no crest and a short row of 8 tubercles at the front of the body in females. The ventral crest in F. nicosiai may be more developed than in F. oustaleti and this species possesses rounded scales >2 mm in diameter behind the eye (which may be absent in F. oustaleti). Patterning is usually different, with a broad lateral stripe characteristic of F. nicosiai. It may not, however, always be possible to distinguish subadult F. oustaleti from male F. nicosiai in areas of western Madagascar where the two species co-occur.
In common with the white-lined chameleon, Oustalet's chameleon has the one of the widest habitat tolerances of any chameleon. It is most often encountered in degraded habitats, agricultural land and human settlements, but also occurs in undisturbed dry forest, montane savannah and, rarely, in tropical rainforest.
Diet: Chameleons were until recently thought to be entirely carnivorous. Recently, Takahashi (2008) reported the first confirmed case of herbivory in Furcifer oustaleti, which were observed to select and consume fruit of the shrubs Grangeria porosa, Chassalia princei and Malleastrum gracile.
Reproductive biology: Maximum and average clutch sizes are unknown, but it is known that females can lay at least 61 eggs in a single clutch, with a combined weight of 56 g. This record is from February, but no other information on the duration of the breeding season is available.
Life cycle: Gestation takes around 40 days, with animals reaching sexual maturity within a year after hatching.
Oustalet's chameleon belongs to a species complex consisting of three recognised species; however, variation between populations and the wide distribution of both Oustalet's and the warty chameleon (F. verrucosus) suggest that both may represent multiple cryptic species. In one population encountered by the author during fieldwork, animals assigned to Furcifer oustaleti (a diagnosis later supported by Frank Glaw) consistently exhibited small size, unusual colouration and patterning; unlike typical F. oustaleti, a white mid-ventral stripe was sometimes present. As these animals co-occurred with typical F. oustaleti, it remains unclear whether they represent a distinct population or species, or whether this colouration and patterning is a consistent feature of subadults in this population.
Glaw, F. and Vences, M. (2007) A Field Guide to the Amphibians and Reptiles of Madagascar. Third Edition. Cologne, Vences & Glaw Verlag: 496pp
Spawls, S., Howell, K., Drewes, R. and Ashe, J. (2004) A Field Guide to the Reptiles of East Africa A&C Black, London: 543pp
Takahashi, H. (2008) Fruit feeding behaviour of a chameleon Furcifer oustaleti: Comparison with insect foraging tactics. Journal of Herpetology 42: 760-763