Bitis arietans Merrem, 1820
Puff Adder
Description
Bitis arietans is a thick, heavily built viper with a large, flattened, triangular head and large upturned nostrils. The fat body terminates into a short, depressed tail (10-15% of total length in males; and 6-9% in females). The Puff Adder is Africas largest viper, with maximum size being a function of locality (Spawls et al., 2002). In Tanzania, Rwanda, Burundi and southern Uganda, adders rarely attain more than 1.2 m (average: 0.7-1.1 m). Males are slightly smaller and brightly coloured than females. Neonates vary from 150-230 mm. The dorsal scales are heavily keeled and are arranged in 27 to 41 rows at midbody. Colouration is quite variable, from yellow-brown to light brown, with yellow or cream, dark-edged chevrons, changing into crossbars towards the tail (Branch, 1998; Spawls et al., 2002). There are dark spots on the head and between the eyes. The belly is yellow or white, with occasional blotches.
Geographical range
The Puff Adder occurs in most of Africa from Eritrea, south to the Cape in South Africa, and west to Senegal. Isolated populations occur in southern Morocco and southwest Arabian Peninsula (Branch, 1998; Spawls et al., 2002).
Local distribution
The Puff Adder is common in the park and in the present survey individuals were seen both during the day and night. Three adders were recorded on one night along the 10 km road from the gate to Tarangire Lodge.
Natural history
This adder occupies a wide range of habitats from semi-desert to woodland, and from sea level to 2200 m. The species is however, absent from desert, dense forest and mountain peaks (over 2400 m). The Puff Adder is terrestrial, but occasionally climbs into low trees and bushes, especially at low altitude, to avoid heat from the ground and sunlight. It is usually nocturnal, but often diurnal during the wet season. During the day, it hides in thick grass, under ground cover, or under bushes. By its sheer size, the Puff Adder is often very poorly concealed under small bushes or in grass tussocks, but well camouflaged by its cryptic colouration, and therefore likely to be stepped on by accident. The Puff Adder emerges at dusk to hunt, usually hiding under cover and ambushing its prey. When disturbed, the snake inflates the body, hissing loudly and threateningly, ready to strike. Puff Adders move sluggishly in a caterpillar fashion, leaving a deep trail. The Puff Adder is Africas most dangerous snake (Branch, 1998; Spawls et al., 2002), and should be approached with extreme caution. It produces cytotoxic venom, which causes extensive swelling, pain and necrosis. Death is unusual, (>10% of untreated cases) but may occur within 2-4 days due to the complications from anaemia and blood poisoning. The diet is variable including small mammals (e.g. hares, mice and rats, squirrels), birds, frogs, lizards and other snakes.
Mating is preceded by combat between rival males. Oestrous females are known to produce a pheromone, which attracts a trail of males. Puff Adders are viviparous, litter size depending on size and altitude (average 20-40 young).
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