Boomslang

Source: Wikipedia, the free encyclopedia.
For other uses, see Boomslang (disambiguation).

Boomslang
Male at campsite in the Ngorongoro Conservation Area

Least Concern  (IUCN 3.1
)
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Suborder: Serpentes
Family: Colubridae
Genus: Dispholidus
Species:
D. typus
Binomial name
Dispholidus typus
(A. Smith, 1828)
Map
Boomslang distribution
  Extant (resident)
Synonyms[1]
  • Bucephalus typus
    A. Smith, 1828
  • Dispholidus typus
    —Boulenger, 1896

The boomslang (/ˈboʊmslɑːŋ/ or /ˈbɔːmsləŋ/; Dispholidus typus) is a highly venomous snake in the family Colubridae.[2] The species is native to Sub-Saharan Africa.

Taxonomy and etymology

Its common name means "tree snake" in

Thelotornis, Thrasops, Rhamnophis, and Xyelodontophis, with which it forms the taxonomic tribe Dispholidini.[4]

Subspecies

Two

nominotypical subspecies.[5]

The

trinomial authority
in parentheses for D. t. typus indicates that the subspecies was originally described in a genus other than Dispholidus.

Description

Raiding the communal nest of sociable weavers

The average adult boomslang is 100–160 centimetres (3.3–5.2 ft) in total length (including tail). Some exceed 183 centimetres (6.00 ft). The

eyes are exceptionally large, and the head has a characteristic egg-like shape. Colouration is highly variable. Males are light green with black or blue scale edges, but adult females may be brown demonstrating sexual dimorphism.[6]

Weight varies from 175 to 510 g (0.386 to 1.124 lb), with an average weight of 299.4 g (0.660 lb).[7]

In this species, the head is distinct from the neck and the canthus rostralis is distinct. The pupil of the very large eye is round. The boomslang has excellent eyesight and often moves its head from side to side to get a better view of objects directly in front. The maxillary teeth are small anteriorly, seven or eight in number, followed by three very large, grooved fangs situated below each eye. The mandibular teeth are subequal. The body is slightly compressed. The dorsal scales, which are arranged in 19 or 21 rows, are very narrow, oblique, strongly keeled, with apical pits. The tail is long, and the subcaudal scales are paired. Ventral scales are 164–201; the anal plate is divided; and the subcaudals are 91–131.[1]

Geographic range

The boomslang is endemic to Sub-Saharan Africa. It is found in South Africa, Eswatini, Mozambique, Botswana, Namibia and north through sub-Sahara Africa.

Habitat

The boomslang is an excellent climber and is highly arboreal, living mainly in forested areas. D. typus lives in karoo shrubs, savannahs, lowland forests, and in grasslands. The boomslang is not restricted to trees and can often be found on the ground hunting, feeding, or taking shelter. It will occasionally hide underground when the weather is harsh.[8]

Reproduction

The boomslang is

oviparous, and an adult female can produce up to 30 eggs, which are deposited in a hollow tree trunk or rotting log. The eggs have a relatively long (3 months on average) incubation period. Male hatchlings
are grey with blue speckles, and female hatchlings are pale brown. They attain their adult colouration after several years. Hatchlings are about 20 cm (7.9 in) in length and pose no threat to humans, but are dangerously venomous by the time they reach a length around 45 cm (18 in) and a girth as thick as an adult's smallest finger.

Behaviour and diet

Boomslang in typical natural habitat

D. typus is

cannibalising members of its own species.[9] During cool weather, the boomslang brumates for short periods, often curling up inside the enclosed nest of a weaverbird
.

Venom

Many venomous members of the family Colubridae are harmless to humans because of small venom glands and inefficient fangs. However, the boomslang is a notable exception in that it has a highly potent venom, which it delivers through large fangs located in the back of the jaw.

haemorrhaging into tissues such as muscle and the brain while at the same time clogging capillaries with tiny blood clots.[2][11] Other signs and symptoms include headache, nausea
, sleepiness, and confusion.

Because boomslang venom is slow-acting, symptoms may not become apparent until many hours after the bite. Although the absence of symptoms provides sufficient time for procuring antivenom, it can also provide victims with false reassurance, leading to their underestimating the seriousness of the bite. Snakes of any species may sometimes fail to inject venom when they bite (a so-called "dry bite"), so after a few hours without any noticeable effects, victims of boomslang bites may wrongly believe that their injury is not serious or life-threatening. The pathophysiological mechanisms of the venom are different with every snake, resulting in different clinical manifestations with every patient.

The snakes of South Africa: their venom and the treatment of snake bite by F. W. Fitzsimmons

An adult boomslang has 1.6 to 8 mg of venom.

intraperitoneal).[15] Based on the very low venom quantities produced by D. typus, and the very serious effects found in a good part of the reported cases in humans, it has been suggested that the venom's LD50 is lower in humans than in mice, with only 2 to 3 mg being enough to potentially kill a healthy adult.[16]

In 1957, herpetologist Karl Schmidt died after being bitten by a juvenile boomslang, which he had doubted could produce a fatal dose.[17][18] He made notes on the symptoms he experienced almost to the end.[19][20] D. S. Chapman reported eight serious envenomations by boomslangs between 1919 and 1962, two of which were lethal.[21]

Boomslang monovalent antivenom was developed during the 1940s. The South African Vaccine Producers manufactures a monovalent antivenom for use in boomslang envenomations.[22] Treatment of bites may also require complete blood transfusions, especially after 24 to 48 hours without antivenom.

The boomslang is a timid snake, and bites generally occur only when people attempt to handle, catch, or kill the animal. When confronted and cornered, it inflates its neck and assumes an S-shaped striking pose.

Gallery

  • A male boomslang
    A male boomslang
  • Boomslang in Western Cape, South Africa
    Boomslang in Western Cape, South Africa
  • Juvenile common boomslang (Dispholidus t. typus)
    Juvenile common boomslang (Dispholidus t. typus)
  • Brown female common boomslang (Dispholidus t. typus)
    Brown female common boomslang (Dispholidus t. typus)

References

  1. ^ a b Boulenger GA (1896). Catalogue of the Snakes in the British Museum (Natural History). Volume III., Containing the Colubridæ (Opisthoglyphæ and Proteroglyphæ) .... London: Trustees of the British Museum (Natural History). (Taylor and Francis, printers). xiv + 727 pp. + Plates I-XXV. (Genus Dispholidus, pp. 186-187; species Dispholidus typus, pp. 187–189, Figure 14).
  2. ^
    ISBN 9781593392925
    .
  3. ^ Oxford English Dictionary. Oxford, England: Oxford University Press. 1989.
  4. doi:10.1017/S0968047002000079
    .
  5. ^ Species Dispholidus typus at The Reptile Database . www.reptile-database.org.
  6. ^ "Boomslang". African Snakebite Institute. 22 October 2017. Retrieved 4 May 2021.
  7. ^ Grassy E MD (June 22, 1940). "Studies on the Venom of the Boomslang". South African Medical Journal.
  8. ^ "Boomslang Snake Facts [Ultimate Guide]". 2011-11-19. Retrieved 2022-04-11.
  9. ^ a b "ADW: Dispholidus typus: INFORMATION". Animal Diversity Web.
  10. ^ Marais, Johan (2004). A Complete Guide to the Snakes of Southern Africa. Second Edition. Struik.
  11. PMID 10775761
    .
  12. ^ "LD50 for various snakes". seanthomas.net. Retrieved 2017-11-14.
  13. ^ Mackessy, Stephen P. (2002). "Biochemistry and Pharmacology of Colubrid Snake Venoms". Journal of Toxicology – Toxin Reviews 21 (1&2): 52. online PDF Archived 2010-06-02 at the Wayback Machine
  14. doi:10.1590/S0104-79301996000100007
    .
  15. PMID 28130154
    .
  16. ^ Mazza, Giuseppe (2011-04-27). "Dispholidus typus". Monaco Nature Encyclopedia. Retrieved 2022-07-09.
  17. ^ "Diary of A Snakebite Death". YouTube.
  18. ^ "The Boomslang Snake Of Africa". www.reptilesmagazine.com. 21 February 2012. Retrieved 2017-11-14.
  19. JSTOR 1439959
    .
  20. Smith, Charles H. "Chrono-Biographical Sketch: Karl P. Schmidt"
    . Some Biogeographers, Evolutionists and Ecologists. Retrieved 9 September 2014.
  21. ^ Bücherl W, Buckley E, Deulofeu V (editors) (1968). Venomous Animals and Their Venoms, Volume I: Venomous Vertebrates. Academic Press. p. 484.
  22. ^ "About Us – South African Vaccine Producers (SAVP)". Archived from the original on 11 April 2021. Retrieved 3 November 2015.

Further reading

External links

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