Colubridae (Colubrids)

Including the genera Boiga, Rhabdophis, Dispholidus and Thelothornis

Most colubrids possess modified supralabial salivary glands which in many cases are in the form of so-called Duvernoy's glands. The saliva produced by such glands may contain various amounts of toxic compounds.

Duvernoy's glands are structures that are homologous to the venom glands of true venomous snakes. Secretions from these glands empty through a duct into the region of the posterior maxillary teeth. In many species, the teeth are elongated in this region. In this regard, colubrids can be divided into those with grooved teeth or fangs (opisthoglyphs) and those without grooved teeth (aglyphs).

The following tables list those colubrids that may possess venomous saliva, on the basis of morphological criteria (elongated or grooved teeth, nature of the glands). The lists have been compiled according to McKinstry (1983). Atractaspis spp. and Homoroselaps spp., which were recently assigned to the Colubridae family, are listed elsewhere. 

Key to the geographical distribution:

New World:

CI          Caribbean Islands
NAm     North America including Mexico
SAm     South and Central America

Old World:

Af         Sub-Saharan Africa
As        Asia

Aus      Australia

EAs      East Asia (in particular China)
Eu        Europe

Ind       Indonesia, the Malay Peninsula and Borneo
Mad     Madagascar
NAf      North Africa including the Sahara
Phil      Philippines

SAs      Southern Asia (India and Sri Lanka, Myanmar, Indochina, in some cases southern China)
WAs     Western Asia (Arabian Peninsula to western Pakistan)

Risk

Secretion of venom through Duvernoy's glands is generally slower than in the true venomous snakes with their highly developed venom glands. Envenoming from a colubrid bite is more likely if the snake does not let go immediately and injects the venom by means of a chewing motion. Nonetheless, very quick bites can also cause envenoming. The opisthoglyphs possess the most efficient venom apparatus amongst the colubrids, as the venom, which is released at the base of the teeth, is channelled into the grooves and can thus flow quickly along the teeth and into the bite.

Serious cases of colubrid envenoming are rare amongst humans and are generally the consequence of handling these snakes. In many cases, the victims are herpetologists or laypersons who collect snakes or keep them in terraria, and who are often quite unaware of the risk. Many colubrids, including opisthoglyphs, are sold as harmless animals.

Minton (1990b) provides an overview of colubrid envenoming.

The dangerous colubrids, which have even been known to cause systemic envenoming, are the opisthoglyphs Dispholidus typus, Thelotornis sp., Malpolon monspessulanus, Boiga irregularis, Tachymenis peruviana and Elapomorphus bilineatus, as well as Rhabdophis sp., an aglyphous genus which can have greatly elongated teeth. The genera Boiga, Rhabdophis, Dispholidus and Thelothornis are discussed in more detail (individual entries below).

The other colubrids have so far only been known to cause local envenoming (see below).

Taxonomy
The Reptile Database