On the Biology of the Chameleons of Southern Arabia II: The Socotra Chameleon, Chamaeleo monachus GRAY, 1865

Here's an English translation of the document titled "Zur Biologie der Chamäleons Süd-Arabiens II. Das Sokotra-Chamäleon, Chamaeleo monachus GRAY, 1865" by Petr Nečas:

Abstract

Following a summary of the taxonomic history of Chamaeleo monachus, the little-known Socotra chameleon is described in terms of its morphology, distribution, natural habitat, and biology. Field observations allow, for the first time, an estimate of its natural reproductive cycle.

Keywords: Sauria, Chamaeleontidae, Chamaeleo monachus Gray, 1865, taxonomy, morphology, natural history, reproductive cycle, Arabia, Yemen, Socotra Island.

Discovery and Taxonomy

The discovery of Chamaeleo monachus was marked by a mistake from the beginning. In 1855, a male specimen of an unknown chameleon species was registered at the British Museum of Natural History in London under catalog number BMNH RR 1946.8.21.98, with the origin listed as "Madagascar." Nine years later, Gray (1864) described this specimen as Chamaeleon monachus, adopting the origin as the type locality. However, in 1880, an expedition led by Prof. Bayley Balfour visited Socotra Island and collected more specimens. Blanford (1881) later corrected Gray's type locality.

The species name monachus is derived from the Greek word "μοναχός" (monachos), meaning "monk." It was likely chosen because the large occipital lobes of the species cover the neck in a way that resembles a monk's hood. Locals on Socotra call the chameleon "Mel'chaibi," and among mountain dwellers, there is a superstition that hearing or feeling the hiss of a chameleon causes muteness.

Its systematic classification has never been disputed. There is only one invalid senior synonym: Chamaeleon verrucosusBlyth, 1853. Klaver & Böhme (1986) placed the species in the subgenus Chamaeleo, which is now invalid due to the elevation of Trioceros to genus status.

Although drawings of C. monachus have been published, colored illustrations are rare. The species is not available for terrarium keeping due to export restrictions from Yemeni authorities and the unique situation of Socotra. Only three specimens have ever been legally exported, and although F1 offspring were produced, further breeding was reportedly unsuccessful.

Morphology

The Socotra chameleon is a slender species, reaching up to 38.5 cm in total length. Most individuals are smaller: males typically measure 33–35 cm, females up to 30 cm. The tail is significantly longer than the head-body length in both sexes.

The body and tail are covered with small round scales interspersed with larger tubercular scales. The throat has longitudinal rows of slightly enlarged scales with narrow interstitial skin fields. A prominent dorsal crest runs from behind the head to the tail, composed of enlarged conical scales. The throat and belly crests are also well-developed.

The head is relatively long with a low casque. The occipital lobes are extremely large—among the largest in any chameleon species—and partially fused behind the casque. Males have a distinct heel spur.

Coloration is variable. Typical colors include green, brown, and black. Males often display light blue markings, while females may show orange zones during pregnancy or post-laying. White or pale green interstitial skin, white throat and belly crests, and dirty white soles and tail undersides are common. Sexual dimorphism includes:

• Thickened tail base in males
• Females are smaller
• Heel spurs only in males
• Blue coloration only in males; orange only in females

Distribution and Habitat

C. monachus is endemic to Socotra Island and is found in many locations, especially in water-bearing wadis where reproduction occurs. Eggs are buried in moist substrate that remains wet for months. The species occurs from sea level up to about 1,000 meters elevation.

Socotra's climate is mild due to its location in the Indian Ocean. Coastal temperatures rarely exceed 35°C and drop below 20°C at night. Rainfall is seasonal and variable. The northeast monsoon in November brings most of the rain, while the southwest monsoon is dry. Coastal areas receive less than 180 mm annually, while the central highlands get over 500 mm. Fog and low clouds provide daily moisture above 800 m.

The chameleons inhabit grass and shrub vegetation (e.g., Croton species) and tree canopies up to 6 meters high, but are most commonly found along vegetated watercourses in deep wadis.

Biology

Little has been known about the biology of this species since its discovery. It is not specifically protected but has been under general conservation measures since Socotra was designated a UNESCO World Natural Heritage Site in July 2008.

The Socotra chameleon is extremely nervous, shy, and sensitive to stress. It moves surprisingly fast and reacts aggressively when handled—hissing, biting, and flaring its occipital lobes to appear larger. Both sexes show aggression toward each other, often biting and threatening with open mouths.

Mating behavior follows typical chameleon patterns. Males court females by displaying bright colors and flattening their bodies. Receptive females remain light green and passive; unreceptive ones turn dark and act aggressively. Copulation can last up to two hours and may be repeated several times.

Females lay 32–52 eggs after a gestation of 30–45 days. Hatchlings emerge after about 120 days and measure around 60 mm. In May 2007, field observations recorded 2 adult males, 4 females, and 19 juveniles at three sites. Nine had just hatched, six were about a week old, and four were about a month old—suggesting that hatching occurs in April–May, with egg-laying in December and mating in October–November.

Schneider (2005) briefly reported on raising individuals from the legally exported specimens described by Schätti & Desvoignes (1999).