Agkistrodon bilineatus

Agkistrodon bilineatus
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Suborder: Serpentes
Family: Viperidae
Genus: Agkistrodon
Species: A. bilineatus
Binomial name
Agkistrodon bilineatus
(Günther, 1863)
Range map for A. bilineatus. Dark blue = A. b. bilineatus, red = A. b. howardgloydi, green = A. b. russeolus, light blue = A. b. taylori.
Synonyms
  • Ancistrodon bilineatus Günther, 1863
  • Ankistrodon bilineatum
    – Müller, 1877
  • Tr[igonocephalus] bilineatus
    – Müller, 1878
  • Ancistrodon bilineatum
    – Dugès, 1896
  • Agkistrodon bilineatus
    – Stejneger, 1899
  • Ancistrodonus bilineatus
    – Herrera, 1899
  • Agkistrodon bilineatus bilineatus
    – Burger & Robertson, 1951
  • Arkistrodon bilineatus
    – Martín del Campo, 1953
  • Trigonocephalus specialis
    Recinos, 1954
  • Agkistrodon b[ilineatus]. bilineatus – Lucas, Dupaix-Hall & Biegler, 1972[2]
Common names: cantil, Mexican cantil, Mexican ground pit viper,[3] Cantil viper,[4] black moccasin,[5] Mexican moccasin,[4] more.

Agkistrodon bilineatus is a venomous pitviper species found in Mexico and Central America as far south as Costa Rica.[2] Four subspecies are currently recognized, including the nominate subspecies described here.[6]

Description

A. b. bilineatus

These are heavy-bodied snakes, and share the same general body structure with cottonmouths. They average around 60 cm (24 in) in length and have a broad, triangular-shaped head with small eyes that have vertical pupils.

Coloration can vary, but most are brown or black, with darker brown or black banding, sometimes with white or cream-colored accents. A. taylori is known for being more elaborately patterned, often having distinct tan-colored banding, sometimes with orange or yellow accents that can almost appear gold in color. There are the following distinctive yellow and/or white lines on the head: a vertical line on the rostral and mental, a fine line on the canthus continuing above and beyond the eye to the neck, a broader line on the upper lip from the anterior nasal to the last labial.[7] Juveniles are almost always distinctly banded, with bright green or yellow tail tips, which they use to lure prey. As they age, their pattern and coloration fade and darken.

Common names

Mexican ground pit viper, Cantil viper,[3][4] cantil,[5] Mexican moccasin,[4] neotropical moccasin,[8] Mexican yellow-lipped viper.[9]

The common name, cantil, is based on the Tzeltal word kantiil, which means "yellow lips."[3]

Geographic range

Mexico and Central America. On the Atlantic side it is found in Mexico in Tamaulipas, Nuevo León, possibly northern Veracruz and Chiapas (in the Middle Grijalva Valley). On the Yucatán Peninsula it occurs in Campeche, Yucatán, Quintana Roo and northern Belize. On the Pacific side it is found from southern Sonora in Mexico south through Guatemala, El Salvador, Honduras and Nicaragua to northwestern Costa Rica. On the Pacific side the distribution is almost continuous, while on the Atlantic side it is disjunct. The type locality given is "Pacific coast of Guatemala."[2]

Conservation status

This species is classified as Near Threatened (NT) on the IUCN Red List of Threatened Species (v3.1, 2001).[1] A species is listed as such when it has been evaluated against the criteria but does not qualify for Critically Endangered, Endangered or Vulnerable now, but is close to qualifying for, or is likely to qualify for a threatened category in the near future. The population trend is down. Year assessed: 2007.[10]

The primary ecological concern is habitat loss.

Behavior

Much like the American cottonmouth, with whom it shares a genus, this species has a reputation for having a nasty disposition and being extremely dangerous, a reputation probably not well deserved. They are generally shy by nature, and if threatened their first instinct is to rely on camouflage. If unable to do so they will use a threat display to ward off potential predators. The tightly coiled animal will raise the last several inches of its tail, this portion often being bright yellow or green in juveniles and a faded yellow or green in adults, the animal will then quickly flick its tail creating a loud whipping sound against its coils or surroundings. This particular behavior is very reminiscent of caudal luring, though in a more violent fashion and is often accompanied by a strike or less commonly a gaping display similar to that of A. piscivorus. They generally will only display these behaviors when given no other choice. In captivity A. bilineatus are often known for aggression stemming from their characteristic lack of predictability.

Reproduction

Breeding occurs in the spring, and like most other viper species, cantils are ovoviviparous, giving birth to 5–20 young at a time.

Captivity

Export from Mexico is not permitted, but cantils of both species are often captive bred, making them frequently available in the exotic pet trade. They are also well represented in zoos throughout North America and Europe.

Venom

According to Gloyd and Conant (1990), "this species is greatly feared throughout its range," in some areas even more so than Bothrops asper. In Sonora, Mexico, it is feared more than any other reptile. In Nicaragua, it is considered the country's most dangerous snake.[11]

Bite symptoms in general may include nothing more than local pain, swelling and discoloration, but those from adult specimens can cause massive swelling and necrosis. Campbell and Lamar (1989) suggested that, due to the necrosis, amputation may be required in one out of every six cases. Some bites were fatal within only a few hours. Gaige (1936) cites one case in which a woman in Motl, Yucatán, Mexico was bitten by a 30 cm (11 3⁄4 in) specimen and died within a few hours. Alvarez del Toro (1983) reports gangrenous tissue falling away in fragments, eventually to expose the underlying bones, describing this is as "spontaneous amputation" of the necrotic wound.[11]

In Honduras, Cruz (1987) describes the bite symptoms as being similar to those of Bothrops species, although more severe considering the small size of these snakes. They include immediate and severe pain, oozing of blood from the fang punctures, considerable edema, epistaxis, bleeding of the gums, marked hematuria, general petechiae, shock, renal failure and local necrosis.[11]

Polyvalent Antivenom, produced by the Instituto Clodomiro Picado in Costa Rica, is used to treat bites from this species.[12]

Subspecies

Subspecies[6] Taxon author[6] Common name[3] Geographic range[3]
A. b. bilineatus (Günther, 1863) Mexican cantil, common cantil The Pacific Coastal Plain from southern Sonora in Mexico, southeast to Guatemala and El Salvador. Also occurs in the Mexican state of Morelos.
A. b. howardgloydi Conant, 1984 Gloyd's cantil The dry Pacific lowlands of Honduras, Nicaragua and Costa Rica.
A. b. russeolus Gloyd, 1972 Yucatecan cantil The Yucatán Peninsula in Mexico in the states of Campeche, Quintana Roo and [Yucatán]], as well as in northern Belize.
A. b. taylori Burger & Robertson, 1951 Taylor's cantil Mexico, in the northeastern states of Nuevo León, San Luis Potosí and Tamaulipas.

Taxonomy

A new subspecies, A. b. lemosespinali, was described by H. M. Smith & Chiszar (2001) based on a single specimen from near Palma Sola, Veracruz, Mexico.[13]

See also

References

  1. 1 2 Lee, J.; Hammerson, G.A. (2007). "Agkistrodon bilineatus". IUCN Red List of Threatened Species. Version 2007. International Union for Conservation of Nature. Retrieved 2017-05-20.
  2. 1 2 3 McDiarmid RW, Campbell JA, Touré T. 1999. Snake Species of the World: A Taxonomic and Geographic Reference, vol. 1. Herpetologists' League. 511 pp. ISBN 1-893777-00-6 (series). ISBN 1-893777-01-4 (volume).
  3. 1 2 3 4 5 Gloyd HK, Conant R. 1990. Snakes of the Agkistrodon Complex: A Monographic Review. Society for the Study of Amphibians and Reptiles. 614 pp. 52 plates. LCCN 89-50342. ISBN 0-916984-20-6.
  4. 1 2 3 4 Mehrtens JM. 1987. Living Snakes of the World in Color. New York: Sterling Publishers. 480 pp. ISBN 0-8069-6460-X.
  5. 1 2 Campbell JA, Lamar WW. 2004. The Venomous Reptiles of the Western Hemisphere. Comstock Publishing Associates, Ithaca and London. 870 pp. 1500 plates. ISBN 0-8014-4141-2.
  6. 1 2 3 "Agkistrodon bilineatus". Integrated Taxonomic Information System. Retrieved 2 November 2006.
  7. ↑ Boulenger, G.A. 1896. Catalogue of the Snakes in the British Museum (Natural History). Volume III., Containing the...Viperidæ. Trustees of the British Museum (Natural History). London. xiv + 727 pp. + Plates I.-XXV. (Ancistrodon bilineatus, pp. 521–522.)
  8. ↑ Gotch AF. 1986. Reptiles – Their Latin Names Explained. Poole, UK: Blandford Press. 176 pp. ISBN 0-7137-1704-1.
  9. ↑ Parker HW, Grandison AGC. 1977. Snakes – a natural history. Second Edition. British Museum (Natural History) and Cornell University Press. 108 pp. 16 plates. LCCCN 76-54625. ISBN 0-8014-1095-9 (cloth), ISBN 0-8014-9164-9 (paper).
  10. ↑ 2001 Categories & Criteria (version 3.1) at the IUCN Red List. Accessed 13 September 2007.
  11. 1 2 3 Warrell DA. 2004. Snakebites in Central and South America: Epidemiology, Clinical Features, and Clinical Management. In Campbell JA, Lamar WW. 2004. The Venomous Reptiles of the Western Hemisphere. Comstock Publishing Associates, Ithaca and London. 870 pp. 1500 plates. ISBN 0-8014-4141-2.
  12. ↑ Agkistrodon bilineatus at Munich AntiVenom INdex (MAVIN). Accessed 27 June 2008.
  13. ↑ Smith H. M., Chiszar D.. 2001. A new subspecies of cantil (Agkistrodon bilineatus) from Central Veracruz, Mexico (Reptilia: Serpentes). Bulletin of the Maryland Herpetological Society, 37: 130-136.
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