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Atheris hirsuta ERNST & RÖDEL, 2002

IUCN Red List - Atheris hirsuta - Data Deficient, DD

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Higher TaxaViperidae, Viperinae, Colubroidea, Caenophidia, Alethinophidia, Serpentes, Squamata (snakes)
Common NamesE: Bristly Tree Viper 
SynonymAtheris hirsuta ERNST & RÖDEL 2002
Atheris hirsuta — DOBIEY & VOGEL 2007
Atheris hirsuta — WALLACH et al. 2014: 62
Atheris hirsuta — SENTER & CHIPPAUX 2022 
DistributionIvory Coast, Ghana, Liberia

Type locality: 6 km west of the “Station de Recherche en Ecologie Tropicale” (SRET, 5° 50’ N, 7° 19’ W), Taï National Park, Ivory Coast.  
TypesHolotype: SMNS 11333 (Stuttgart) 
DiagnosisDiagnosis. Slender tree viper with rather short head, IOD (Interorbital distance) / SED (Snout-eye distance) = 2.3; heavily carinated scales, especially on head and neck, giving the snake a bristly appearance; keels. run in long curves towards a sharp tip; six suprarostrals; eight to nine infralabials; three pairs of sublinguals; elongate dorsal scales; 16 scale rows around mid-body.

Comparisons: Atheris hirsuta sp. nov. resembles A. squamigera in appearance but can be distinguished from the latter by several morphometric, and morphological characters. Its most intriguing difference is the elongated dorsal scalation, especially on the head and anterior body, which could not be observed to such an extent in any specimens of A. squamigera. Further distinguishing characters were: the number and arrangement of suprarostrals (SRO) (six in A. hirsuta; three or up to eight inA. squamigera, but usually odd numbers occur); the number of pairs of sublinguals (PSL) (three pairs in A. hirsuta; four to seven in A. squamigera); and the shape of the head and neck scales. Scales in A. squamigera are never as strongly bent as in A. hirsuta (Fig. 2 d, e), which in this respect appears similar to A. hispida and A. acuminata. Atheris hirsuta has a much shorter snout and larger eye than A. squamigera, giving the head a more blunt and stocky appearance. This is expressed by the IOD/SED index, which is 2.3 in A. hirsuta, compared with a maximum of 1.9 (mean 1.7) in A. squamigera. The number of mid-dorsal scale rows (MSR) in the holotype of A. hirsuta is comparatively low - only 16, which equals the lowest counts found in A. squamigera (SMNS 4213; 2MB 20481).
Atheris hirsuta differed from the sympatric A. chlorechis by the number of suprarostrals (7-8 in A. chlorechis, arranged in alower row offour and an upper row of three to four scales) and the maximum transverse head scale count (MTHS) between the posterior supralabials (SL) (25-27 in A. chlorechis; 14 in A. hirsuta). Atheris chlorechis has higher infralabial counts (IL) (10-11; 8-9 in A. hirsuta) and higher numbers of dorsal scale rows at mid-body (25-37). Scales of A. chlorechis are not as strongly keeled and the keel only stretches across two thirds o f the entire scale, leaving a smooth, slightly depressed area uncovered. Our SEM-photos o f A. hirsuta revealed no serration o f keels on lateral scales, known to occur in some A. chlorechis (Groombridge, 1980, cited by Broadley, 1996, 1998).
Atheris hirsuta differs from the East African species A. nitschei, A. rungweensis, A. desaixi, A. katangensis and A. ceratophora by having fewer transverse head scales, fewer interocunasals (ION) and higher numbers of dorsal scale rows at mid-body. Dorsal scalation in these species is never as elongate as in A. hirsuta. The latter lacks serrated keels on lateral scales, present in the species mentioned above. The lack of elongate supraoculars that form hom-like projections above the
eyes furthermore distinguishes A. hirsuta from A. ceratophora. Keels in A. rungweensis and A. desaixi end before the scale tip, whereas they reach the tip in the other members of this group, as well as in A. hirsuta. A. rungweensis and A. desaixi have more interoculabials (IOL), as well as higher numbers of infralabials. The number of pairs of sublinguals is higher in A. desaixi. Atheris broadleyi from Cameroon is distinguished from A. hirsuta by having more interoculabials, a higher number of scale rows at mid-body and fewer interorbitals (IOS), and by its consistent dorsal colour pattern, also used to distinguish it from the closely related A. squamigera (Lawson, 1999). Two distinctive East African species, A. hispida and A. acuminata, also posses acuminate or lanceolate dorsal scales, but differ from A. hirsuta by having fewer transverse head scales and a lower number of suprarostrals, as well as fewer pairs ofsublinguaIs. In addition, A. hispida has a higher number of interocunasals. Atheris acuminata has a lower number of circumorbital scales, as well as lower numbers of supralabiaIs. For a summary of differences between A. hirsuta and other Atheris species, see Table 4 (in Ernst & Rödel 2002).

Coloration. Dorsal coloration in life is bronze; several scale tips and keels being dark-brown, forming an irregular pattern of broken crossbars; ventrally cream-white to yellowish; iris yellow (Fig. 3). In preservative (3 % formaldehyde transferred to 70 % ethanol after two months), colour changed to reddish-brown dorsally; ventral scales turned uniform clear reddish brown, being more intense in posterior third of body and tail, fading anteriorly.

The key to the genus Atheris on p. 74 of Chippaux & Jackson 2019, says that A. hirsuta can be distinguished from A. hispida by its possession of only one row of scales between the eye and the nasal, while in reality it has two rows, as can be seen in the original description of A. hirsuta and on the photos provided by Penner et al. (2013) and by Chippaux and Jackson themselves (Pauwels & Brecko 2020). 
CommentVenomous! Closely related to A. squamigera.

Habitat: trees (arboreal) 
EtymologyThe name refers to the hirsute appearance of the snake (lat. hirsutus = hairy, hirsute). 
  • Chippaux, Jean-Philippe & Kate Jackson 2019. Snakes of Central and Western Africa. Johns Hopkins University Press, 448 pp. [detaileld review in HR 51 (1): 161] - get paper here
  • Dobiey, M. & Vogel, G. 2007. Venomous Snakes of Africa - Giftschlangen Afrikas. Edition Chimaira, Terralog 15, 150 pp. - get paper here
  • Ernst, R. & Rödel, M. O. 2002. A new Atheris species (Serpentes: Viperidae), from Taï National Park, Ivory Coast. The Herpetological Journal 12: 55-61 - get paper here
  • HUGHES, B. 2017. VIPERIDAE: Atheris hirsuta Ernst & Rödel 2001 Bristly Tree Viper - BRISTLY TREE VIPER IN GHANA. African Herp News (65): 34-35 - get paper here
  • PAUWELS, O. S. G., AND J. BRECKO 2020. Book Review: Snakes of Central and Western Africa. Herpetological Review 51: 161-164.
  • PENNER, JOHANNES; LEGRAND NONO GONWOUO, MARK-OLIVER RÖDEL 2013. Second record of the West African hairy bush viper Atheris hirsuta Ernst & Rödel, 2002 (Serpentes: Viperidae). Zootaxa 3694 (2): - get paper here
  • Phelps, T. 2010. Old World Vipers. Edition Chimaira, Frankfurt, 558 pp. [critical review in Sauria 33 (3): 19 and HR 43: 503]
  • Schlüter, A. & Hallermann, J. 1997. The Type Specimens in the Herpetological Collection of the Staatliches Museum für Naturkunde in Stuttgart. Stuttgarter Beitr. Naturk. Ser. A (553): 1-15 - get paper here
  • Senter, P. J., & Chippaux, J. P. 2022. Biogeography of snakes in Liberia: Review and synthesis of current knowledge. Ghana Journal of Science, 63(1), 29-62 - get paper here
  • TRAPE, JEAN-FRANÇOIS & CELLOU BALDÉ 2014. A checklist of the snake fauna of Guinea, with taxonomic changes in the genera Philothamnus and Dipsadoboa (Colubridae) and a comparison with the snake fauna of some other West African countries. Zootaxa 3900 (3): 301–338 - get paper here
  • Wallach, Van; Kenneth L. Williams , Jeff Boundy 2014. Snakes of the World: A Catalogue of Living and Extinct Species. [type catalogue] Taylor and Francis, CRC Press, 1237 pp.
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