Rhinoceros Viper

Large and stout, it ranges in total length (body + tail) from 72 to 107 cm (about 28 to 42 inches). Spawls et al. (2004) mentioned a maximum total length of 120 cm (47 in), but admitted this is exceptional, quoting an average total length of 60–90 cm (about 24–35 inches). Explorer Harry Johnston (1858 – 1927) mentions in his book 'Liberia' (1906) that adult "puff-adders" of the species B. nasicornis and B. gabonica (gaboon viper) grow to "between four and five feet" (about 120 to 150 cm) in Liberia. He also states that: "in case of the horned puff-adder, the young when born are a foot long" (~30 cm), which is 20 to 65 percent longer than the average birth length given by Spawls et al. (2004): 18–25 cm (7–10 in). Females grow larger than males. The head is narrow, flat, triangular and relatively small compared to the rest of the body. The neck is thin. It has a distinctive set of two or three horn-like scales on the end of the nose, the front pair of which may be quite long. The eyes are small and set well forward. The fangs are not large: rarely more than 1.5 cm (0.59 in) long. Midbody there are 31–43 dorsal scale rows. These are so rough and heavily keeled that they sometimes inflict cuts on handlers when the snakes struggle. There are 117–140 ventral scales and the anal scale is single. Mallow et al. …

B. nasicornis is found from southern Guinea, Sierra Leone and Liberia to Ghana in West Africa, and in Central Africa in the Central African Republic, southern Sudan, Cameroon, Gabon, Congo, DR Congo, Angola, Rwanda, Uganda and western Kenya. The type locality is listed only as "interior parts of Africa." It mainly occurs in forested areas, rarely venturing into woodlands. Its range is therefore more restricted than B. gabonica.

Primarily nocturnal, they hide during the day in leaf litter, in holes, around fallen trees or tangled roots of forest trees. Their vivid coloration actually gives them excellent camouflage in the dappled light conditions of the forest floor, making them almost invisible. Although mainly terrestrial, they are also known to climb into trees and thickets, where they have been found up to 3 m (9.8 ft) above the ground. This climbing behavior is aided by a partially prehensile tail. They are sometimes found in shallow pools and have been described as powerful swimmers. They are slow moving, but capable of striking quickly, forwards or sideways, without coiling first or giving a warning. Holding them by the tail is not safe; as it is somewhat prehensile, they can use it to fling themselves upwards and strike. They have been described as generally placid creatures, less so than B. gabonica, but not as bad-tempered as B. arietans. When approached, they often reveal their presence by hissing, said to be the loudest hiss of any African snake—almost a shriek. These adders also make a sort of hissing noise through their nose as part of their respiratory function.