Common names: bush vipers.

Atheris is a genus of venomous vipers found only found in tropical subsaharan Africa, excluding southern Africa. Confined to rain forest areas, many members have isolated and fragmented distributions. In an interesting example of convergent evolution, they show many similarities to the arboreal pit vipers of Asia and South America. Eight species are currently recognized.

Description

Relatively small in size, with adults ranging in size from 40 cm (A. katangensis) to a maximum of 78 cm (A. squamigera).

All species have a broad, triangular head that is distinct from the neck. The canthus is also distinct and the snout is broad. The crown is covered with small imbricate or smooth scales, none of which are enlarged. The eyes are relatively large eyes with elliptical pupils. The eyes are separated from the supralabials by 1-3 scale rows and from the nasal by 2-3 scales.

The body is slender, tapering and slightly compressed. The dorsal scales are overlapping, strongly keeled and have apical pits. Laterally these are smaller than the middorsals. Midbody there are 14-36 rows of dorsal scales. There are 133-175 rounded ventral scales. The subcaudal scales are single and number 38-67. The tail is strongly prehensile and can support the body while suspended from a branch or a twig.

Members of this group come in an amazing variety of colors and patterns, often within a single species. A. ceratophora and A. squamigera are particularly variable.

Geographic range

Tropical subsaharan Africa, excluding southern Africa.

Some species have only isolated populations, surviving in small sections of ancient rainforest. It is obvious that they once had a much wider distribution, but are now declining.

Habitat

Rainforest regions, mostly in remote areas far from human activity. Some species are threatened by habitat destruction.

Behavior

All species are strictly arboreal, although they can sometimes be found on or near the ground.

Feeding

Atheris species have been known to prey upon a variety of small amphibians, lizards, rodents, birds and even other snakes. Some species or populations may specialize in eating frogs, but most have been described as opportunistic feeders. Prey is typically ambushed from a hanging position, held until it has succumbed to the venom and then swallowed.

Reproduction

All Atheris species are ovoviviparous. Food may be refused during the African "winter" months of July and August. Mating takes place in September-November and the females give birth to live young in March and April.

Captivity

A. squamigera is reported to do very well in captivity, needing only something to climb on and having no particular temperature requirements. Captive specimens take mice and small birds. However, there have been reports of cannibalism.

Venom

Not much is known about their venom except that it is strongly hemotoxic, causing pain, swelling and blood clotting problems. Until recently, their venom has often been regarded as less toxic than that of many other species, perhaps because bites are uncommon, but this turned out not to be the case. There are now a number of reports of bites that have led to severe hemorrhaging. One case was fatal. Atheris-specific antivenin does not exist and antivenins meant for bites from other species seem to have little effect, although Echis antivenin has been reported to have been of some help in a case of A. squamigera envenomation.

Species

Species	Taxon author	Subsp.*	Common name	Geographic range
A. anisolepis	Mocquard, 1887	0		West central Africa: Gabon, Congo, west DR Congo, north Angola.
A. ceratophora	Werner, 1895	0	Horned bush viper	The Usambara and Uzungwe Mountains in Tanzania.
A. chlorechisT	(Pel, 1851)	0	Western bush viper	West Africa including Guinea-Bissau, Guinea, Sierra Leone, Liberia, Ivory Coast, Ghana, Togo, Benin, isolated locations in Nigeria, Cameroon, Equatorial Guinea and Gabon.
A. desaixi	Ashe, 1968	0	Mount Kenya bush viper	Two isolated populations in Kenya: in the forests at Chuka, south-eastern Mount Kenya, and Igembe in the northern Nyambeni range.
A. hispida	Laurent, 1955	0	Spiny bush viper	Central Africa: DR Congo, south-west Uganda, west Kenya.
A. katangensis	Witte, 1953	0	Upemba bush viper	Restricted to Upemba National Park, Shaba Province in eastern DR Congo.
A. nitschei	Tornier, 1902	1	Great Lakes bush viper	Central Africa from east DR Congo, Uganda and west Tanzania southward to north Malawi and north Zambia.
A. squamigera	(Hallowell, 1854)	0	Variable bush viper	West and central Africa: Ivory Coast and Ghana, eastward through southern Nigeria to Cameroon, southern Central African Republic, Gabon, Congo, DR Congo, northern Angola, Uganda, Tanzania (Rumanika Game Reserve), western Kenya and Bioko Island.

*) Not including the nominate subspecies.
^T'') Type species.

Taxonomy

Other species may be encountered in literature, such as:

• A. acuminata - Broadley, 1998 - western Uganda
• A. broadleyi - Lawson, 1999 - Cameroon (East Province)
• A. hirsuta - Ernst & Rödel, 2002 - Ivory Coast
• A. rungweensis - Bogert, 1940 - south-west Tanzania, north-east Zambia, north Malawi
• A. subocularis - Fischer, 1888 - Cameroon (Southwest Province), extreme east Nigeria

Until relatively recently, these species, all of which are terrestrial, were also included in the genus Atheris:

• Adenorhinos barbouri, Uzungwe viper (Loveridge, 1930)
• Montatheris hindii, Montane viper, (Boulenger, 1910)
• Proatheris superciliaris, Lowland viper, (Peters, 1855)

Together with Atheris, these four genera are sometimes referred to as the tribe Atherini.

See also

• List of viperine species and subspecies
• Snakebite

References

Further reading

External links

• Bush vipers at Corallus.com Accessed 2 August 2007.