Chamaeleo (Trioceros) johnstoni
Scientific name Common name(s) alternate scientific names described by year size brood

Chamaeleo Trioceros johnstoni

Johnston's or Ruwenzori Three-Horned Chameleon Chamaeleon johnstoni, Chamaeleon gaueri, Chamaeleon johnstoni graueri, Chamaeleon laevivulgaris, Chamaeleo johnstoni crenulatus
see a species list of Chamaeleo
Boulenger 1901 Medium Eggs

Johnston's chameleon is found in abundance across equatorial central Africa (Congo, Burundi, Rwanda, Ruwenzori and Virunga Ranges of Western Uganda, and Eastern Republic of Congo (Zaire). They are indigenous to the high, moist savannahs and montane forests where temperatures range from 55-85ºF (13-29ºC). Average day time temperatures are between 72-83ºF with night time drops to 50-60ºF. Day time humidity ranges from 60% in the dry season to 80% in the rainy season. Night time humidity is considerably higher. C. johnstoni primarily inhabit trees at heights of 12-18 feet (3-4 meters)

C. johnstoni is similar in appearance to C. jacksonii but with a deeper body. Males of the nominate form (C. johnstoni johnstoni) have annulated horns; two preocular and one rostral. Females lack horns. (Note: in the subspecies C. johnstoni ituriensis both sexes lack horns). The horns may be up to 3 cm in length. There is a flattened casque which lacks occipital lobes and extends only slightly past the back of the skull. Large, lenticular scales adorn the body, throat and limbs. Gular and dorsal crests are absent. Basic coloration is of a light green with 3-5 vertical bands of turquoise and/or yellow. When stressed, the animal turns to a darker brown pattern with lighter colored bands. Females often have yellow markings on the head. They typically reach 12 inches in total length (weight: 90-110 grams) with exceptional specimens reaching 15". Females average 10" and weigh 50-80 grams) Gravid specimens may weigh 70-90 grams. In addition to lacking horns, females often exhibit yellow on the head. Females also have more homogeneous scalation, are slightly smaller and lack the hemipenal bulge.

Temperament toward conspecifics is not overly aggressive compared to most chameleons. They are quite shy, particularly the Burundi variant. The Rwenzori variant is somewhat less so. There has been some success maintaining C. johnstoni in groups of 1 male: 2-3 females in a large 3'x3'x6' densely planted enclosure. For more standard sized cages, individual housing is strongly recommended. Gravid females must always be kept individually. Males must never be housed in anything other than complete physical and visual isolation from each other. Lots of simulated rainfall with high humidity is critical, as is a sharp night time temperature drop of 15-20ºF. All of the standard chameleon prey items are accepted. C. johnstoni also evidences a particular fondness for terrestrial snails.

Eight-18 eggs (average 14) are typically laid in a single clutch. This number increases with age. Only one clutch is usually laid per year but 2 clutches in a year have been observed. Hatching rates of 80-100% have been reported. Sexual Maturity occurs at 10-12 months. Incubation is in Vermiculite or Perlite at either 20-21ºC permanent (68/69ºF) or preferably at 21ºC (69ºF) day/18ºC (64ºF) night. The oft-recommended incubation temp. of a consistent 22.5ºC (72ºF) is too high and produces weak hatchlings!! Hatching time is approximately 120 days. When eggs start to turn dark transfer to 'hatching-tank' with moss etc on the ground and a few thin branches inside. Cover eggs carefully with a layer of leaves, grass, etc., thus forcing hatchlings to dig themselves out and providing them with opportunity to climb up right away. This technique prevents accidents with Vermiculite and better mimics the natural state. Never squeeze hatchlings out of eggs!! The hatching process may take up to two days.

Contributed by Wulf Schott

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Spawls, S., Howell, K., Drewes, R., and Ashe, J. 2002. A Field Guide to the Reptiles of East Africa. Academic Press, New York.

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