Fig. 4.52 Dispholidus typus. Note the short head and large eyes.

  Fig. 4.53 Thelothornis kirtlandii in a threat display, with inflated throat.

Distribution

See link "Distribution" at the top of the page for detailed information.

  Map 23 

 Thelotornis spp.

 Dispholidus typus.

Biology

Arboreal colubrids found in bushes and shrubs. Sometimes also found on the ground.

Dispholidus on average 1.2–1.5 m, maximum of over 1.8 m. Thelotornis on average 1.2 m, maximum of around 1.8 m. Slender body. Thelotornis is extremely slender and laterally somewhat flattened. Head of Dispholidus oval and high with a short snout and remarkably large eyes. Round pupils. Head of Thelotornis elongated, with shallow indentations on each side from the eye to the tip of the snout. Eyes relatively large, pupils in the form of a horizontal keyhole. The dorsal body scales of Dispholidus are distinctively carinate, and in Thelotornis less markedly so. Both genera normally possess three greatly enlarged and grooved venom fangs at the level of the eyes.

Colouring: Basic colouring of Thelotornis light-gray to gray-green. Light transverse spots with a dark border that are connected to each other. Belly greenish to grayish, speckled with brown. Colouring and body shape create an overall impression that resembles a dry branch. Dispholidus has no markings, but has variable colouring of green, brown or almost black. Odd scales may be green, blue, yellow or brown. Snakes with green colouring sometimes have black edges to their scales. Young animals mostly have brownish or yellowish colouring.

The habitat of Dispholidus is open savanna or scrubland in sub-Saharan Africa, but not in extremely dry zones, and rainforest areas. Thelotornis inhabits rainforests, gallery forests and savanna areas. Both are numerous in these habitats.

When in danger they try to retreat immediately. If unsuccessful, they inflate their throat. Although neither genus is considered aggressive, they are prepared to bite once in this defensive pose. After biting, they do not disengage straight away, and it is sometimes necessary to remove them by force. 

Risk

Apart from the Asian Rhabdophis subminiatus and R. tigrinus, Dispholidus and Thelotornis are the only colubrids that have been proven to have caused isolated fatalities. Their venom is extraordinarily potent, so that even small amounts are able to cause serious envenoming. However, despite their dangerousness, envenoming rarely occurs. These shy animals do not strike readily, so that most bites are the consequence of deliberate handling of these snakes by the victim. Furthermore, in many cases a bite does not actually result in delivery of venom. 

Literature (biological)

Broadley 1983, 2001, Broadley and Cock 1989, Minton et al. 1965, Pitman 1974, Roman 1980, Sweeny 1971, Visser and Chapman 1978, Welch 1982