Marshall's pygmy chameleon

Marshall's pygmy chameleon
Conservation status
Vulnerable  (IUCN 3.1)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Squamata
Family:	Chamaeleonidae
Genus:	Rhampholeon Peters, 1868
Species:	R. marshalli
Binomial name
Rhampholeon marshalli Boulenger, 1906

Marshall's pygmy chameleon (Rhampholeon marshalli), also called Marshall's leaf chameleon or Marshall's dwarf chameleon, is a species of chameleon found in the forests of Zimbabwe and Mozambique in Africa. It grows from 3.5 to 7.5 cm (1.25 to 3 in) and feeds on insects. When standing still, it resembles a leaf on a branch.

Identification

Marshall’s leaf chameleon is unmistakable. It is the only such tiny chameleon in its range (sympatric with Chaemeleo dilepsis quilensis, the flap-necked chameleon to a degree). This is a tiny species of 3.2-7.5 cm (females being slightly larger). Isolated populations have distinct size variations; for example, those found just to the north of Mutare appear to be larger than those just to the south (separated by deep valleys). It has a dorsoventrally flattened head and body with prominent ribs and apparent venation, giving it the appearance of a leaf. Its colour variations are from deep brown to yellowish green according to the camouflage required for the situation. Males are usually more brightly coloured.

Sexing

Males, being slightly smaller, having a distinct penial swelling at the base of the tail, and a greener throat with a row of defining white or yellow tubercle spots, are relatively easy to distinguish from females.

Sympatric species

Little habitat overlap occurs as that of C. dilepsis approaches the range of Marshall's leaf chameleon. C. dilepsis is rare, found in low, probably transitory population densities at the altitudes inhabited by R. marshalli, preferring the sunnier grasslands and forest margins.

Related species

Rhampholeon gorongosa Broadley 1971, once considered a subspecies, is found in similar habitats on the Mt Gorongosa Massif in adjacent Mozambique. It was discovered by the ornithologist Stuart Irwin. Rhampholeon platyceps is found in similar habitats on the Mt Mulanje in adjacent Malawi.

Karyotopic taxonomy

Wright 1973 confirms the number and form of the chromosomes from specimens provided by Broadley put R. marshalli in the genus Rhampholeon with Rhampholeon spectrum, the type species for the genus having 36 pairs of chromosomes like the other members of this genus.

Distribution

This species is found largely in the Eastern Highlands of Zimbabwe and the adjacent upland forest of Mozambique.

Habitat

The patches of relict montane forest found in the Nyanga, Bvumba, Himalaya and Chimanimani Mountains are the primary habitats. They can be found in the cool, damp interior of the forest, mostly in the undercanopy and on the forest margins. These forest patches are surrounded by vast expanses of montane grassland, but are often so far apart as to be isolated from one another, but forest along the numerous mountain streams may link these very limited habitats. Marked specimes surveyed over a long time appeared not to travel far at all, usually less than 15 m.

Natural history

Rhampholeon marshalli seems to inhabit the subcanopy and leaf litter of the relict cloudforests. Major canopy trees include Syzigium and Ficus. These forest are rich in fern and liane species. Forest margins have prickly species of Ilex and Rubus briars. How far up the canopy these creatures ascend is not known, but they tend to be found in the leaf litter or low shrubs. The winters in these (evergreen) forests are sharp and very cool; a period of brumation seems llikely to occur for these tiny lizards. They eat insects, though these forests seem to be fairly depleted now.

Reproduction

In the rains (November to March), Marshall's leaf chameleon lays a small clutch of embryonated eggs that hatch quickly. Humphreys photographed a gravid female excavating a hole in the forest soil and laying a clutch. One egg was exhumed and found to contain a fully developed embryo. After 35 days, the eggs hatched and the tiny juveniles dispersed. Juveniles are relatively large at 22–25 mm long.

Conservation

Like other small mountain chameleons, this species appears to have population spikes and collapses. Their ranges do not appear to be threatened and much of their habitat is safe in Zimbabwe in the Nyanga National Park (where introduced tree species of wattle and pine are being eradicated to allow natural forest to re-emerge), Stapleford Forest Reserve, Bunga National Park and Botanical Garden, the Chimanimani National Park, and the Mt Chirinda Forest Reserve. However, the tiny relict cloudland patches are under constant threat from clearance for coffee, tea and protea plantations, and excessive collection of firewood, and the corridors that once connected populations have indubitably diminished.

References

• Broadley & Blake, 1978. A preliminary report on a field survey of Marshall's Dwarf Chameleon Rhod Sci News 5, 10 pp 310–314

• Broadley & Blake, 1979. A field study of Rhampholeon marshalli on Vumba Mountain, Rhodesia (sauria : Chamaeleonidae). Arnoldia 34, (8) pp 1–7
• Wright & Broadley, 1973. Chromosome and the status of Rhampholeon marshalli Boulenger . Bulletin of Sthrn Calif. Acad Sciences 72 (3) pp 164–165

• Longmanns animal encyclopedia - Pg. 422