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Agkistrodon taylori: Difference between revisions

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Agkistrodon taylori
Conservation status
Least Concern  (IUCN 3.1)[1]
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Squamata
Suborder:	Serpentes
Family:	Viperidae
Genus:	Agkistrodon
Species:	A. taylori
Binomial name
Agkistrodon taylori Burger & Robertson, 1951
Synonyms[2][3]
Agkistrodon bilineatus [In part] Taylor, 1940 Agkistrodon bilineatus taylori (nomen nudum) Smith & Taylor, 1950 Agkistrodon bilineatus taylori Burger & Robertson, 1951 Agkistrodon taylori Parkinson, et al. 2000

Agkistrodon taylori is species of venomous snake, a pitviper (Crotalinae) found only in northeastern Mexico. The standardized names are Taylor's cantil (English)^[4][5][3] and Metapil (Spanish),^[4] although it is sometimes called the ornate cantil^{[6]: 51 p.} as well as several other colloquial names. It was named in honor of American herpetologist Edward Harrison Taylor.^{[7]: 261 p.}

It is a stout, medium sized snake, averaging 64-90 cm. in length. Taylor's cantils have prominent light and dark stripes on the head, with a pattern of black and gray-brown bands on the body, accented with white, yellow, and orange. They are sexually dimorphic, with males being significantly darker than females. Some older individuals, particularly males, may grow darker, nearly black with age. It is a viviparous species, with typical litters of 3 to 10 live young. Taylor's cantils are uncommon to rare snakes in the wild and listed as a threatened species in Mexico. It occurs in a variety of habitats on the Gulf Coastal Plain and lower foothills of the Sierra Madre Oriental, including thorn scrub, tropical deciduous forest, and grasslands, sometimes said to prefer ecotones between scrubland and forest in the vicinity of rocky limestone outcroppings. Although not overtly aggressive, it is known to be very defensive with a volatile temper and may be quick to strike when approached, threatened, or restrained. No case reports of human envenomations have been published. Its venom is believed to be similar to its close relative, the cantil Agkistrodon bilineatus, and potentially fatal.^{[5]: 97-103 p. [3]: 265-266 p. [8]: 215-221 p. [9]: 395-396 p.}

Etymology

The original description states that the specific, or trivial name, was "Named for Dr. Edward H. Taylor in recognition of his many contributions to our knowledge of the Mexican herpetofauna."^{[10]: 213 p.} Indeed, Taylor's extensive publications on Mexico's amphibians and reptiles, culminating with the "Herpetology of Mexico",^[11] published in collaboration with his student Hobart M. Smith, is the foundation of modern Mexican herpetology. Taylor's work on Mexico alone would have secured him a prominent reputation in the field of herpetology. However, Taylor made equally important contribution to Philippine land mammals, the herpetofauna of the Philippines, herpetofauna of the south-central United States, Eumeces (skinks of the world at that time), the herpetofauna of Costa Rica, the herpetofauna of Thailand, and caecilians of the world.^{[12] : 145 p. [13]: 83 p.}

The common name cantil is believed to have its origins in the language of an indigenous people of Chiapas, Mexico, the Tzeltal. The Tzeltal word "kantiil" was given to the snake meaning yellow lips (kan = yellow, tiil = lips). The name is thought to have first entered herpetological literature in the publication of Albert Günther's Reptilia and BatrachiainBiologia Centrali-Americana,^{[14]: 186 p.} and later popularized in the writings of Raymond L. Ditmars.^[15]

Taxonomy and Phylogenetics

Recent molecular studies^[16][17][18] have produced strong evidence indicating that pitvipers made a single invasion into the New World, presumably via the Bering Land Bridge in the early Tertiary or late Cretaceous, with a subsequent divergence resulting in a northern temperate group (including Agkistrodon, Crotalus, and Sistrurus) and a Neotropical group.^{[17]: 93 p.} Of the Old World pitvipers, Gloydius is believed to be phylogenetically closest to New World pitvipers.^{[18]: 103 p.} The molecular evidence indicates the genus Agkistrodonismonophyletic, and suggest that copperheads, (Agkistrodon contortrix) are the most basal living lineage of the genus, with the cottonmouths (Agkistrodon piscivorus) basal to Taylor's cantil (A. taylori), and A. taylori basal to the remaining cantils of Latin America.^{[16]: 416 p.}

The taxonomic history of Taylor's cantil (Agkistrodon taylori) is relatively simple and straight forward compared to many species.

Agkistrodon bilineatus, In part: Edward H. Taylor collected what was to become the holotype of A. taylori, on June 9, 1938, "crawling on the highway pavement about dark" very near the Tamaulipas, Nuevo Leon state line. Using the name Agkistrodon bilineatus, he published a detailed description of the specimen including color, pattern and scale data, noting some differences compared with the head of a specimen from Michoacán.^{[19]: 486 p.} Agkistrodon bilineatus taylori, Nomen nudum: Taylor and Hobart Smith published the name in a checklist of type localities of Mexican herpetofauna.^{[20]: 346 p.} However, the list was published before the subspecies formal description, thus making the name a nomen nudum, a technical term for a scientific name that is invalid because it is not associated with any published description, definition, or holotype of a taxon.^{[21]: 210 p.} Taylor and Smith knew of the impending description, published about 19 months after their checklist. The authors acknowledged "Our attention was first called to this interesting situation by Dr. Edward H. Taylor.....to whom we are indebted for permission to study it", and Hobart Smith for his "advice and assistance".^{[10]: 213 p.} Agkistrodon bilineatus taylori: Formally described as subspecies in 1951, the holotype is in the collection of the University of Illinois Museum of Natural History (UIMNH 10002). It has been transferred between collections a number of times and identified as: EHT-HMS 5514 (Edward H. Taylor and Hobart M. Smith collection);^[19] EHT 5514 (Edward H. Taylor collection);^[10] and INHS 5514 (Illinois Natural History Survey).^[22] It is a young male, 383 mm. snout-vent length, and 82 mm. tail length (465 mm. total length). A paratype was also designated, Chicago Natural History Museum 28794, an adult male from "no more than a few mile from the type locality".^{[10]: 213-215 p.} For the remainder of the 20th century the taxonomic status remained unchanged. ^{[5]: 97 p.} Agkistrodon taylori: Taylor's cantil was elevated to species status in research published in 2000, based on a combination of mitochondrial DNA sequences, its geographic isolation (allopatry), unique aspects of head and body colour pattern, and sexual dichromatism (sexual dimorphism) in adults.^{[16]: 418 p.} Subsequent taxonomic reviews and species accounts supported the recognition of A. taylori as a specie.^{[3]: 265 p. [8]: 215 p. [6]: 52 p.}

Description

Adults of A. taylori usually attain a total length (including tail) of 64–90 cm (25+1⁄4–35+3⁄8 in), with some growing to 96 cm (37+3⁄4 in). The species has a heavy body and a relatively long tail: 16-19% of total body length in males and 13-18% in females. ^[3]

Distribution

Agkistrodon taylori is endemictoMexico. It occurs primarily in southern Tamaulipas,^[23] with one record near the coast as far north as Carboneras.^[24] Elevations typically range from near sea level to about 500 m., with a maximum elevation of 919 m. in San Luis Potosi.^{[5]: 101 p.} The type locality is "21 km north of Villagrán, Tamaulipas, Mexico".^[10] It has been speculated that A. taylori occurs in the Sierra de San Carlos, based on the local inhabitants identifying photographs,^[23] however no confirmed records from the mountain range are available.^[24]

There are also a few of scattered records from lower elevations on the eastern slopes and canyons of the Sierra Madre Oriental. These include a number of records from Nuevo Leon as far north as Monterrey,^[23] south to the vicinity of El Naranjo, San Luis Potosi, ^{[5]: 100 p.} Atlapexco^[25] and Huejutla de Reyes, Hidalgo, and near Tantoyuca, Verecruz.^[26]

A southernmost record represents a single specimen from near Palma Sola, Veracruz, that was first described as a subspecies, Agkistrodon bilineatus lemosespinali,^[27] however more recent accounts considered the defining characters of A. b. lemosespinali fell within the normal range of A. taylor.^{[3]: 266 p.} And yet another more detailed study concluded Agkistrodon bilineatus lemosespinali appeared to be more closely related to, if not the same as, Agkistrodon bilineatus.^[26]

Ecology and natural history

Zoos have reported on the longevity of captive specimens including a male that lived 15 years, 7 months, and 19 days.^{[28]: 33 p.} Another individual that arrived at a zoo as an adult live 17 years and 5 months and was estimated to be ca. 19 years 11 months at the time it dead.^[29]

Habitat

The preferred natural habitatsofA. taylori are forest, grassland, and freshwater wetlands.^[1]

Diet

Information on the diet of wild Taylor's cantils is minimal. The information that is available suggest A. taylori is a diet generalist, similar to other species in the genus. One study found fecal analysis of recently collected snakes contained grasshopper remains and hair from unidentified mammals. Two individuals manually palpated to regurgitate yielded a Mexican pocket mouse (Liomys irroratus = Heteromys irroratus) and a white-footed mouse (Peromyscus leucopus).^{[23] : 381 p.}

Juveniles have been observed using the yellowish tips of their tails as a lure to attract prey, a behavior known as caudal luring and recorded in several species of snakes. "The tail was elevated in a vertical position, approximately four cm (1.5 in) above the snake's body, and the tail tip was being wriggled."^[30]

In captivity adults have accepted lab mice, house mice, hamsters, and brown rats, neonates have been fed fish, small frogs, and baby pink mice, and one case of cannibalism has been reported when an adult female consumed an adult male cage mate. ^{[5]: 102 p. [8]: 220 p.}

Reproduction

A. tayloriisviviparous.^[22]

The Bronx Zoo reported an unusual incidence of twinning in Taylor's cantil, when two snakes were observed in one egg sac membrane at birth. Although the twins were proportionate in size to the rest of the clutch with no apparent deformities, of eight young, the twins were significantly smaller than their siblings and one did not survive long after birth. It is unknown if they were identical or fraternal.^[31]

Conservation status

Enigmatically, the IUCN Red List of Threatened Species ranked Agkistrodon taylori as a species of least concern.^[1] In reality, it has been listed as a threatened species for decades by the Mexican Federal Government and is protected by Mexican law.^[32] No comprehensive studies have been made of A. taylori populations in the wild however, assessments of its conservation status elicit statements such as "this species faces a bleak future due to habitat destruction for agriculture"^{[8]: 221 p.} and "Urgent measures may be required to ensure continued existence of the biogeographically important and spectacularly coloured Taylor's cantil."^{[16]: 418 p.} A 2013 taxonomic reevaluation and conservation assessment of cantils was subtitled ":a race against time".^{[6]: 48 p.} On recent conservation evaluations using the Environmental Vulnerability Score (EVS) [low, 3–9; medium, 10–13; high, 14–20], Agkistrodon taylori was rated 17, a species of high vulnerability.^{[33]: 93 p. [34]: 616 p.}

Colloquialisms and folklore

Paul S. Martin wrote that the name "cantil" was unknown in the Gómez Farías region of southwest Tamaulipas and that "metapil" was occasionally used by residents, and might refer to A. taylori.^{[35]: 77 p.} In contrast, Pat Burchfield of the Gladys Porter Zoo wrote that he had never heard that name used in the eastern and coastal regions of Tamaulipas and the farmers and ranchers there referred to a freshwater fish as metapil, however the name "navaja" was sometimes used for both Boa constrictor and A. taylori. Locals described a short, heavy, very aggressive snake that could jump and bite, and sting with its tail which they called "hueson" (big bone) and "cola hueso" (bone tail).^{[23]: 377 p.}

Captivity

Keeping venomous animals as pets is generally discouraged. Additionally, many national, state, and municipal govern ments regulate the possession and transportation of venomous reptiles, and if not entirely prohibited, the possession and transportation of venomous reptiles and other exotic wildlife are often subject to restrictions or require permits.^{[36]: 6 p.}

Because of its attractive coloration and relatively small size, A. taylori are occasionally seen in the exotic pet trade, with captive bred individuals sometimes available. The care and requirements are similar to A. contortrix. This species is not for the inexperienced keeper. The venom of A. taylori is significantly stronger than that of A. contortrix and can cause severe tissue damage and potentially death if untreated.

Gallery

• 
  A juvenile Taylor's cantil (Agkistrodon taylori)
• 
  A female Agkistrodon taylori
• 
  Close up view of a female Agkistrodon taylori
• 
  Taylor's cantil (Agkistrodon taylori) photographed in the field in southern, Tamaulipas, Mexico (24 October 2004)

References

Further reading

External links

Wikimedia Commons has media related to Agkistrodon bilineatus.

• Agkistrodon taylori at the Reptarium.cz Reptile Database. Accessed 7 December 2007.