Agkistrodon taylori

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Agkistrodon taylori

Least Concern  (IUCN 3.1)[1]
Scientific classification Edit this 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 a species of venomous snake, a pitviper (

Crotalinae) found only in northeastern Mexico. The standardized names are Taylor's cantil (English)[3][4][5] 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

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.[3]: 265–266 p. [5]: 97–103 p. [8]: 215–221 p. [9]
: 395–396 p. 

Etymology

The original description states that the specific, or

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

Raymond L. Ditmars.[15] However, later authors questioned that attribution, as the Tzeltal are highland people and unlikely to have had significant contact with the species. Alternatively, "can" or "canti" meaning "viper", and "nil" meaning snake, are used in a more widespread Mayan language that might be the origin of the name cantil.[3]
: 263 p. 

Taxonomy and Phylogenetics

Phylogenetic relationships of Agkistrodon based on Parkinson et al. (2000),[16] modified with updated taxonomy

Recent molecular studies

Agkistrodon contortrix) are the most basal (ancestral) 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:

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,
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
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

A female Taylor's Cantil photographed in the field in southern Tamaulipas, Mexico among the rocks in its natural habitat (11 September 2007)

Size: Taylor's cantils, and

anal plate is undivided and the tip of the tail terminates in a small, downturned, spine-like scale.[3]: 266 p. [5]: 98–100 p. [8]
: 216–217 p. 

Taylor's cantil can be distinguish from other members of the genus

supralabial scales to the lower margin of the scale, to the mouth line (lower margin of supralabial scales have a narrow dark stripe or dark pigment in A. bilineatus, A. howardgloydi, and A. russeolus). Agkistrodon taylori is also the only species in the genus to exhibit an obvious sexual dimorphism.[3]: 350 & 261 p. [5]: 98 p. [8]
: 158 p. 

Distribution

Distribution of Agkistrodon taylori: circle = type locality of A. taylori; square = type locality of A. bilineatus lemosespinali

Agkistrodon taylori is

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

Verecruz.[26] A number of photographic records been reported on the social network iNaturalist, filling gaps in the distribution of previously published records, particularly in Nuevo Leon, San Luis Potosi, and Veracruz.[27]

A southernmost record represents a single specimen from near Palma Sola, Veracruz, which was first described as a subspecies, Agkistrodon bilineatus lemosespinali,[28] 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

The fact that A. taylori was not described until 1951 and known only from two specimens at that time is some indication of its rarity.[10] Paul S. Martin's work in Tamaulipas from 1948 to1953 encompassed 12 collectors and 14 months of fieldwork yielding only three specimens, and he noted interviews with two lifelong resident farmers that indicated they had seen "only one other snake of this type".[29]: 8 & 77 p.  Likewise, a six year field survey in the 1970s noted "A few woodcutters we queried had encountered A. b. taylori and they concurred that it is rare in the area."[23]: 377 p.  Several studies have commented on the scarcity of museum specimens available for research, including a landmark 1990 monographic review of the genus Agkistrodon which identified only 19 specimens, a 2007 study on Hidalgo, San Luis Potosi, and Veracruz populations identifying only one from each state, and a 2013 study reported only 27 specimens from Tamaulipas.[5]: 97 p. [24]: 642 p. [26]: 536 p. 

As a rare and threatened species, Patrick Burchfield of the Gladys Porter Zoo in Brownsville, Texas, focused special attention on Taylor's cantil for conservation efforts and conducted field surveys 1974-1979 that provided much of what is known about the natural history of the species.[5]: 97 p. [16]: 418 p.  Taylor's cantil was found to be most active in the months of October to March, which is the cool and rainy season in the region. It is predominantly corpuscular and nocturnal, but is occasionally known to be active on rainy or overcast days.[23]: 381 p. 

Several authors have commented on the temperamental nature of A. taylori. If blocked from a clear retreat, cornered, harassed, restrained, or handled it may be quick to strike. "When provoked, specimens of taylori lash their tails from front to back and side to side in typical cantil fashion, meanwhile striking out repeatedly. Sometimes one will move so violently that it actually will leave the ground."[23]: 377 p. 

Zoos have reported on the longevity of captive specimens including a male that lived 15 years, 7 months, and 19 days.[30]: 33 p.  Another individual that arrived at a zoo as an adult lived 17 years and 5 months and was estimated to be ca. 19 years 11 months at the time it died.[31]

Habitat

thorn scrub, about 68 km. east-southeast of the type locality, with the Sierra de San Carlos
in the background (14 July 2007)
Tropical scrubland and tropical deciduous forest with the Rio Guayalejo and Cerro del Bernal in the Municipality of Gonzlaez, Tamaulipas, Mexico (17 April 2001)

Agkistrodon taylori is found in a variety of habitats, including mesquite-grassland,

tropical Veracruz moist forests in the south. Gulf coastal grasslands and scrublands near sea level occur in the east and the foot hills and canyons of the Sierra Madre Oriental
occur in the west of its range.

The

El Naranjo, San Luis Potosi,[5]: 101 p.  in a vegetation zone described by Paul S. Martin as tropical semi-evergreen forest[29]: 33 p.  It has been reported from disturbed, secondary growth, in areas of tropical deciduous forest.[25]

Field surveys conducted in the 1970s noted that collecting in

riparian zones failed to yield specimens, indicating that Taylor's cantil is not closely associated with wetlands. The favored habitat was found to be open canopied woodlands with limestone outcrops and rock-strewn hillsides. The preferred habitat was in areas of an ecotone between arid tropical thorn scrub and tropical semi-deciduous forest, which included trees such as Texas ebony (Pithecellobium flexicaule [= Ebenopsis ebano]) and strangler fig (Ficus sp.). Large terrestrial bromeliads, "wild pineapples" (Bromelia sp.), armed with sharp spines, grow in the understory, in some areas forming dense, impenetrable thickets providing shelter for the snakes.[23]: 377–378 p.  Recent decades have seen a significant increase in agriculture and development in these areas of Tamaulipas, significantly reducing wildlife habitat.[16]
: 418 p. 

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 =

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."[33]

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

Like all members of the genus, Agkistrodon taylori is viviparous.[22] Most of what is known about the reproduction of A. taylori comes from captive specimens in zoos. Like many species of snakes, males have been observed to engage in a ritualized "combat dance" in captivity on several occasions. This behavior could be compared to arm wrestling. Typically two males, in the vicinity of a female, will intertwine their bodies and attempt to raise their heads higher than their opponent's, while trying push down or pin the other snake's head to the ground. Normally the loser retreats unharmed and the winner mates with the female.[34]: 128 p.  However in at least one case in captivity, a male Taylor's cantil was unable to escape its opponent in confinement, and after 12 days was ultimately killed by its cage mate. "Post-mortem revealed a bite puncture wound in the heart area with severe hemorrhaging in the tissue"[23]: 381 p. 

A juvenile Taylor's cantil with lighter colors and a yellow tail

Courtship and copulation have been observed in captivity mostly from November to February (rarely as early as mid September). If these months reflect activities in the wild, mating occurs in the October to March cool and wet season.[23]: 376 & 381 p.  Copulation is known to last an hour and a half to three hours.[8]: 219 p.  Births have been reported from early May to July,[8]: 219–220 p. May to September,[3]: 258 p. and June to October.[23]: 3 p.  Litters have ranged from three to eleven young (average 8), 17.2 – 27 cm. (average 23.7 cm.) in total length, and average 12.1 grams (16 g. maximum) in weight.[8]: 219–220 p. 

Neonates are patterned like adults, including characters of sexual dimorphism, but much lighter in color (comparable to Agkistrodon piscivorus). The colors of the young have been described as less intense than adults with various shades of darker and lighter grays and creamy yellow,[23]: 378 p. and bright cream, yellow, or salmon colored.[8]
: 219 p. 

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.[35]

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.[36] 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.[37]: 93 p. [38]
: 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.[29]: 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 imperator 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 governments regulate the possession and transportation of venomous reptiles, and if not entirely prohibited, the possession and transportation of venomous reptiles and other exotic wildlife often require permits and are subject to restrictions.[39]: 6 p.  The illegal collecting of this threatened species for the pet trade has been implicated as one of several conservation threats.[38]: 604 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 female Agkistrodon taylori
    A female Agkistrodon taylori
  • Close up view of a female Agkistrodon taylori
    Close up view of a female Agkistrodon taylori
  • A male Taylor's cantil (Agkistrodon taylori) photographed in the field in southern, Tamaulipas, Mexico (24 October 2004)
    A male Taylor's cantil (Agkistrodon taylori) photographed in the field in southern, Tamaulipas, Mexico (24 October 2004)

References

  1. ^ a b Lavin-Murcio, P, F. Mendoza-Quijano, G. A. Hammerson (2007). Agkistrodon taylori. The IUCN Red List of Threatened Species. Version 2014.3. Downloaded on 13 April 2015.
  2. ISBN 1-893777-01-4
    (volume).
  3. ^
    ISBN 0-8014-4141-2
  4. ^ a b Liner, E. A. and G. Casas-Andreu. 2008. Standard Spanish, English and scientific names of the amphibians and reptiles of Mexico. Society for the Study Amphibians and Reptiles. Herpetological Circular 38: i-iv, 1-162. (pages 95-96)
  5. ^
    ISBN 0-916984-20-6
  6. ^ a b c Porras, Louis W., Larry D. Wilson , Gordon W. Schuett, and Randall S. Reiserer.2013. A taxonomic reevaluation and conservation assessment of the common cantil, Agkistrodon bilineatus (Squamata: Viperidae): a race against time. Amphibian & Reptile Conservation , 7 (1):48-73.
  7. ISBN 978-1-4214-0135-5
    . (Agkistrodon bilineatus taylori, p. 261).
  8. ^
    ISBN 0-8018-9875-7
  9. ISBN 978-3899731002
  10. ^ a b c d e f g Burger, W. Leslie and William B. Robertson. 1951. A New Subspecies of the Mexican Moccasin, Agkistrodon bilineatus. The University of Kansas Science Bulletin. University of Kansas Publications, Museum of Natural History. 34(5): 213-218.
  11. ^ Smith, H. M. and E. H. Taylor. 1966. Herpetology of Mexico: Annotated Checklist and Keys to the Amphibians and Reptiles. A reprint of Bulletins 187, 194 and 199 of the U. S. National Museum with a list of subsequent taxonomic innovations. Eric Lundberg, Ashton, Maryland.
  12. ^ Taylor, Edward H., A. B. Leonard, H. M. Smith, and G. R. Pisani. 1975. Edward H. Taylor: Recollections of an Herpetologist. Monograph of the Museum of Natural History, University of Kansas. 4: 1-159.
  13. ISBN 0-916984-19-2
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  14. ISBN 0-916984-17-6
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  15. ^ Conant, Roger. 1982. The origin of the name "cantil" for Agkistrodon bilineatus. Herpetological Review 13(4): 118.
  16. ^ a b c d e f g Parkinson, C. L., K. R. Zamudio, and H. W. Greene. 2000. Phylogeography of the pitviper clade Agkistrodon: historical ecology, species status and conservation of cantils. Molecular Ecology 9: 411-420.
  17. ^
    ISBN 0-9720154-0-X
  18. ^ a b Castro, T. A. and C. L. Parkinson, 2006. Bayesian mixed models and the phylogeny of pitvipers (Viperidae: Serpentes). Molecular Phylogenetics and Evolution 39: 91-110.
  19. ^ a b Taylor, Edward H. 1940 (1939). Some Mexican Serpents. The University of Kansas Science Bulletin. University of Kansas Publications, Museum of Natural History.26(14): 445-487.
  20. ^ Smith, Hobart M. and Edward H. Taylor, 1950. Type Localities of Mexican Reptiles and Amphibians. University of Kansas Science Bulletin, 33: 313-380.
  21. ^ Lillywhite, Harvey B. 2008. Dictionary of Herpetology. Krieger Publishing Co. Malabar, Florida. viii, 376 pp. ISBN 1-57524-023-8
  22. ^ a b Uetz, P., Freed, P, Aguilar, R. & Hošek, J. (eds.) (2021) The Reptile Database, http://www.reptile-database.org, Agkistrodon taylori Burger & Robertson, 1951 (accessed 20 July 2021)
  23. ^ a b c d e f g h i j k l m Burchfield, Patrick M. 1982. Additions to the Natural History of the Crotaline Snake Agkistrodon bilineatus taylori. Journal of Herpetology. 16(4): 376-382.
  24. ^ a b c Farr, William L., David Lazcano and Pablo A. Lavin-Murcio. 2013. New Distributional Records for Amphibians and Reptiles from the State of Tamaulipas, Mexico III. Herpetological Review 44(4): 631-645
  25. ^ a b Tovar-Tovar, Hector and Fernando Mendoza-Quijano. 2001. Agkistrodon taylori. .Herpetological Review. 32(4): 276-277.
  26. ^ a b c Bryson, Jr., Robert W. and Fernando Mendoza-Quijano. 2007. Cantils of Hidalgo and Veracruz, Mexico, with Comments on the Validity of Agkistrodon bilineatus lemosespinali. Journal of Herpetology.41(3): 536-539.
  27. ^ iNaturalist, Observations, Taylor's Cantil (accessed 25 July 2021)
  28. ^ Smith, Hobart M. and David Chiszar. 2001. A New Subspecies of Cantil (Agkistrodon bilineatus) from Central Veracruz, Mexico (Reptilia: Serpentes). Bulletin of the Maryland Herpetological Society. 37(4): 130-136.
  29. ^ a b c d Martin, Paul S. 1958. A Biogeography of Reptiles and Amphibians in the Gómez Farías Region, Tamaulipas, Mexico. Miscellaneous Publications, Museum of Zoology University of Michigan, 101: 1-102.
  30. ^ Snider, A. T. and J, K. Bowler. 1992. Longevity of reptiles and amphibians in North American collections. Society for the Study Amphibians and Reptiles. Herpetological Circular 21: iii, 40.
  31. ^ O'Shea, Mark, Steve Slater, Jamie Wood. 2012. Herpetology Notes. Agkistrodon taylori (Taylor's cantil) longevity. Herpetological Review 43(4):609
  32. ^ Terán-Juarez, SA, and García-Padilla, E. 2014. Geographic Distribution. Agkistrodon taylori (Taylor's Cantil). Herpetological Review. 45(2): 284.
  33. ^ Strimple, Pete 1995. Comments on caudal luring in snakes with observations on this behavior in two subspecies of cantails Agkistrodon bilineatus ssp. Liueratura Serpentium, 15(3): 74-77.
  34. ISBN 0-520-20014-4
  35. ^ Titus, Valorie R. and C. Drew Foster. 2015. An incidence of twinning in Taylor's cantil (Agkistrodon taylori) at the Wildlife Conservation Society's Bronx Zoo. Herpetological Review 46(3): 371-373.
  36. ^ SEMARNAT (Secretaría de Medio Ambiente y Recursos Naturales). 2019. Norma Official Mexicana, NOM-059-SEMARNAT-2019, protección ambiental-especies nativas de México de flora y fauna silvestre-categorías de riesgo y especificaciones para su inclusión, exclusión o cambio-lista de especies en riesgo. Diario Oficial de la Federación. México, D.F., Mexico.
  37. ^ Terán-Juárez, S. A., E. García-Padilla, V. Mata-Silva, J. D. Johnson, and L. D. Wilson. 2016. The herpetofauna of Tamaulipas, Mexico: composition, distribution, and conservation. Mesoamerican Herpetology 3: 43–113.
  38. ^ a b Nevárez-de los Reyes, M., D. Lazcano, E. García-Padilla, V. Mata-Silva, J. D. Johnson, and L. D. Wilson. 2016. The herpetofauna of Nuevo León, Mexico: composition, distribution, and conservation. Mesoamerican Herpetology 3: 558–638.
  39. ISBN 978-0-544-12997-9

Further reading

External links

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