Animal: Various Colubridae, Colubrids
Taxonomy
Common names
Distribution
Worldwide
Biology
The family of Colubridae consists of species with various types of dentition and salivary glands. All of them are 'non front fanged' in contrast to the representatives of the families of Elapidae and Viperidae (incl. Viperinae and Crotalinae).
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 and those without grooved teeth (aglyphous).
Atractaspis spp. and Homoroselaps spp., which were recently assigned to the Colubridae family, are now taxonomically assigned to the Atractaspididae.
Danger
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) as well as Weinstein et al. (2023) provide 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, Dispholidus, Rhabbdophis and Thelotornis are discussed elsewhere in more detail (individual entries below).
Other colubrids have so far only been known to mainly cause local envenoming.
Literature (biological)
Minton 1990b, Weinstein et al. 2011 and 2014