Gaboon Viper

The Gaboon viper (Bitis gabonica), also called the Gaboon adder, is a large and highly venomous species of viper found in the rainforests and savannas of sub-Saharan Africa. It is the largest member of the genus Bitis. Like all other vipers, it is venomous, and it has the longest fangs of any venomous snake – up to 2 inches (5.1 cm) in length – and the highest venom yield of any snake. No subspecies are recognized.

Taxonomy

The Gaboon viper was described in 1854 as Echidna gabonica.

Lenk et al. (1999) discovered genetic differences between the two conventionally recognized subspecies of B. g. gabonica and B. g. rhinoceros. According to their research, these two subspecies are as genetically different from each other as they are from B. nasicornis. Consequently, they regard the western form as a separate species, B. rhinoceros.

The snake's common names include Gaboon viper, butterfly adder, forest puff adder, whisper, swampjack, and Gaboon adder.

Originally a name given by the Portuguese, Gabon (Gabão) refers to the estuary on which the town of Libreville was built, in Gabon, and to a narrow strip of territory on either bank of this arm of the sea. As of 1909, Gaboon referred to the northern portion of French Congo, south of the equator and lying between the Atlantic Ocean and 12°E longitude.

Description

Adults are typically 125–155 cm (4.10–5.09 ft) in total length (body and tail). The maximum total length of this species is often cited as 205 cm (81 in) for a specimen collected in Sierra Leone, but individuals from this locale are now reclassified as Bitis rhinoceros. The sexes may be distinguished by the length of the tail in relation to the total length of the body: around 12% for males and 6% for females. Adults, especially females, are very heavy and stout. One female measured at 174 cm (69 in) in total length, a head width of 12 cm (4.7 in), a width or circumference of 37 cm (15 in), and a weight of 8.5 kg (19 lb).

In their description of B. gabonica, Spawls et al. (2004) give a total length of 80–130 cm (31.5–51 in), with a maximum total length of 175 cm (69 in), saying the species may possibly grow larger still. They acknowledge reports of specimens over 1.8 m (5.9 ft), or even over 2 m (6.6 ft) in total length, but claim no evidence supports this. A large specimen of 1.8 m (5.9 ft) total length, caught in 1973, was found to have weighed 11.3 kg (25 lb) with an empty stomach. It is the heaviest venomous snake in Africa and one of the heaviest in the world along with the king cobra and eastern diamondback rattlesnake.

The head is large and triangular, while the neck is greatly narrowed, only about one-third the width of the head. A pair of "horns" is present between the raised nostrils—tiny in B. gabonica. The eyes are large and moveable, set well forward, and surrounded by 15–21 circumorbital scales. The species has 12–16 interocular scales across the top of the head. Four or five scale rows separate the suboculars and the supralabials, with 13–18 supralabials and 16–22 sublabials. The fangs may reach a length of 55 mm (2.2 in), the longest of any venomous snake.