| Agkistrodon bilineatus | |
|---|---|
| Conservation status | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Subphylum: | Vertebrata |
| Class: | Reptilia |
| Order: | Squamata |
| Suborder: | Serpentes |
| Family: | Viperidae |
| Subfamily: | Crotalinae |
| Genus: | Agkistrodon |
| Species: | A. bilineatus |
| Binomial name | |
| Agkistrodon bilineatus (Günther, 1863) |
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| Range map for A. bilineatus. Dark blue = A. b. bilineatus, red = A. b. howardgloydi, green = A. b. russeolus, light blue = A. b. taylori. | |
| Synonyms | |
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Agkistrodon bilineatus is a venomous pitviper species found in Mexico and Central America as far south as Costa Rica.[1] Four subspecies are currently recognized, including the nominate subspecies described here.[5]
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These are heavy bodied snakes, and share the same general body structure with cottonmouths. They average around 60 cm (23.6 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.[6] 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.
Cantil,[2][3] common cantil,[4] Mexican moccasin,[3] tropical moccasin,[7] Mexican cantil.[8]
The common name, cantil, is based on the Tzeltal word kantiil, which means "yellow lips."[2]
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 Yucatan 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."[1]
This species is classified as Near Threatened (NT) on the IUCN Red List of Threatened Species (v3.1, 2001).[9] 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.
Much like the American cottonmouth, this species has a reputation for having a nasty disposition and being extremely dangerous, a reputation probably not well deserved. They are shy by nature, and if threatened their first instinct is usually to flee. If unable to flee they will threat display by raising their head and sometimes opening their mouth. They generally will strike only if given no other choice.
Breeding occurs in the spring, and like most other viper species, cantils are ovoviviparous, giving birth to 5-20 young at a time.
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.
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 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[5] | Taxon author[5] | Common name[2] | Geographic range[2] |
|---|---|---|---|
| A. b. bilineatus | Günther, 1863 | 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 | Castellana | 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 Leon, San Luis Potosí and Tamaulipas. |
A new subspecies, A. b. lemosespinali, was described by Smith and Chiszar (2001) based on a single specimen from near Palma Sola, Veracruz, Mexico.[13]