Biology:Florida cottonmouth

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Short description: Species of snake

Florida cottonmouth
Mocassin d'eau.jpg
Scientific classification edit
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Suborder: Serpentes
Family: Viperidae
Genus: Agkistrodon
Species:
A. conanti
Binomial name
Agkistrodon conanti
Gloyd, 1969[1]

The Florida cottonmouth (Agkistrodon conanti) is a species of venomous snake, a pit viper in the subfamily Crotalinae of the family Viperidae. The species is endemic to the United States, where it occurs in southern Georgia and the Florida peninsula in nearly every type of wetlands in the region, including brackish water and offshore islands. However, it is not entirely dependent on water and is occasionally encountered as far as a mile (1.6 km.) from surface water. Agkistrodon conanti venom is very hemolytic and known to cause relatively extensive necrosis compared to many snake venoms, and can sometimes be lethal with a 17% mortality rate.[2]:211 p. It is often confused with harmless watersnakes (Nerodia) and other semi-aquatic species with which it shares its habitat.

It is a moderately large, thick bodied snake, adults averaging 30 to 48 inches (76-122 cm) in length, but rare individuals can exceed 6 feet (183 cm). The head is marked with conspicuous black cheek stripes on each side, set off by light cream or white stripes above and below. The body is olive brown, dark brown, to black and with 10 to 17 dark bands. The dark bands are often darker at the edges but lighter with irregular markings or spotting in the center. The snakes often grow darker with age, and the banding and patterns can be obscure or absent on adults. It is a viviparous species, normally giving birth to 6 to 8 young, which bear the same pattern as adults but are clay-red or "red dirt" in color. It was first described in the late 1960s as a subspecies, Agkistrodon piscivorus conanti, however molecular research published in 2015 justified elevating it to a full species.[3]:215-225 p.[4]:249-274 p.[2]:193-215 p.[5]:437-438 p.[6]

Etymology

In the original description, Howard K. Gloyd wrote it was "named in honor of a friend and colleague, Roger Conant, Director of the Philadelphia Zoological Garden, whose professional achievements and dynamic promotion of the study of herpetology for amateurs merit highest commendation."[7]:230 p. Roger Conant wrote Reptile Study for the Boy Scouts of America's merit badge series and the original Peterson Field Guide to Reptiles and Amphibians of Eastern and Central North America, one of the most popular and authoritative field guides on North American herpetofauna. He was a leading authority on North American watersnakes (Nerodia),[8] and with Gloyd, he coauthored a seminal monograph on the genus Agkistrodon.[3] Conant also named the southern cantil (Agkistrodon howardgloydi) in honor of Gloyd.[9]:141 p.[10]

Taxonomy and phylogenetics

The Florida cottonmouth is one of eight species in the genus Agkistrodon that includes the copperheads, cottonmouths, and cantils. Molecular evidence indicates the genus Agkistrodon is a monophyletic group, meaning they all share a common ancestor. The copperheads (Agkistrodon contortrix and A. laticinctus) are the most basal (ancestral) living lineage of the genus, with the cottonmouths (Agkistrodon piscivorus and A. conanti) basal to Taylor's cantil (A. taylori), and A. taylori basal to the remaining cantils of Latin America.[11]:416 p. The northern cottonmouth (Agkistrodon piscivorus) is the sister taxon (closest relative) of the Florida cottonmouth (Agkistrodon conanti).[12]:513 p.

The Florida cottonmouth was first described as a subspecies, Agkistrodon piscivorus conanti, as recently as 1969. The holotype is a young adult male in the United States National Museum (USNM 165962), and the type locality is "at the edge of Rochelle-Cross Creek Road, about 7 miles southeast of Gainesville, Alachua County, Florida" . Seven additional paratypes were designated in the original description.[7]:226 p. Agkistrodon conanti was elevated to a full species in 2015 based on molecular data, phylogenetic evidence, and distinct ecological niches.[13][12] Several subsequent reviews and species accounts supported the recognition of Agkistrodon conanti as a species.[6][5]:437 p.[14]

Description

Top row: northern cottonmouth; bottom row, Florida cottonmouth; although the facial patterns are variable in both species, the overall lighter, cleaner face markings are characteristic of the Florida cottonmouth and the two dark vertical lines on the snout are diagnostic of the species)[7]

Adults of A. p. conanti grow up to 1,892 mm (74.5 inches) in total length (including tail). Allen and Swindell (1948) reported one male specimen from Marion County, Florida that measured 1,829 mm (72 inches) in total length and weighed 4.6 kg (10 pounds).[3]

The color pattern is very similar to that of A. piscivorus, apart from head markings that are plainly visible even in older darker specimens of A. conanti: with dark postocular stripes that are bordered above and below by narrow light lines. A pair of dark stripes are also visible at the front of the lower jaw. Mature specimens often lack any dorsal pattern, while the dorsal patterns of juveniles are more pronounced.[15]

The Florida cottonmouth (Agkistrodon conanti) differs from the northern cottonmouth (Agkistrodon piscivorus) in having a pair of dark vertical lines at the tip of the snout (running down the seams of the rostral, prenasals, and first supralabial scales). Additionally the patterns and markings on the head of the Florida cottonmouth are typically lighter, cleaner, and more sharply defined in all except a few old individuals.[7]:227-228 p. Agkistrodon conanti also has a longer tail, mean relative tail length 17.4% in adult and subadult males (mean relative tail length 15.9% in adult and subadult males in Agkistrodon piscivorus).[3]:216 p.

The cottonmouths differs from all other members of the genus Agkistrodon in the absence of a loreal scale and 25 mid-body dorsal scale rows, rarely 23 or 27 (mid-body dorsal scale rows typically 23 [rarely 21 or 25] and loreal scale present in all other species). Additionally, the third supralabial usually reaches the eye orbit (small scales are usually between supralabials and the eye orbit in all other species).[3]:55 p.[4]:250 p.

Distribution

Geographic distribution of the two species of cottonmouth, Agkistrodon piscivorus and Agkistrodon conanti; black dots represent the type localities

Agkistrodon conanti is found in the southeast of the United States, throughout the Florida peninsula, including many barrier islands and keys, and into southern Georgia. The Florida cottonmouth ranges into the Florida Keys at least as far as Key Vaca. The exact origin of a 19th century record from Key West is questionable, although by the end of the 20th century, no additional records had appeared and no suitable habitat remains there.[3]:219 p.

Sources vary on the exact areas and extent of the zone of integration between A. conanti and A. piscivorus. Earlier subspecies accounts all mapped different and various regions of integration.[3]:208-209 p.[4]:271 p.[16]:403 p. In one study ecological niche models predicted hybridization might occur from North Carolina to the southern coastal plains in southeastern Louisiana,[12]:516 p. however molecular data (DNA) from the same study indicated samples from individuals from the Savannah, Georgia area northward, as well as from areas north and west of Mobile Bay, Alabama were A. piscivorus (with the exception of a single hybrid from southern Mississippi).[12]:507 p.

Ecology and natural history

Habitat

A. conanti, Big Cypress National Preserve, Florida

According to Wright and Bishop (1915), in the Okefenokee Swamp A. conanti occurs in thickets along the edges of the cypress ponds of the islands, around the wooded edges of stretches of water, in areas where the woods of the islands meet pine woods, and throughout the swamp in general.[3]

In the Everglades, Allen and Swindell (1948) mentioned that it can be found in palmetto clumps as much as a quarter mile from water. Otherwise these snakes tend to aggregate around drying water holes, most likely because of the increasing concentration of available prey. Duellman and Schwartz (1958) described the species as inhabiting aquatic environments, cypress flats and wet prairies, but not pine forests, scrub or hammocks. The latter is contradicted by a report from northern Florida where large numbers were seen in wet pine-palmetto areas, except during very dry periods.[3]

Reproduction

Agkistrodon conanti is ovoviviparous, and while there is no specific mating season, most births occur during the summer months. Females generally only breed every other year and give birth to between one and 15 young per litter. The average total length of each newly born snake is 18 cm (7.1 in).

Colloquialisms and folklore

Colloquial names for the Florida cottonmouth include aquatic copperhead, aquatic moccasin, cotton-mouthed snake, gaper, gapper, lake moccasin, mangrove rattler, moccasin viper, North American water viper, pond moccasin, river pit viper, short-tailed moccasin, small-tailed rattler, snap jaw, stub-tail moccasin, swamp lion, swamp moccasin, trap jaw, water mamba, water moccasin, water pilot, water pit moccasin, water rattlesnake, white mouth moccasin, and worm-tailed moccasin.[17]

Gallery

  • Florida cottonmouth (Agkistrodon conanti) at the Cincinnati Zoo

  • Florida cottonmouth (A. conanti) from Alachua County, Florida (23 March 2011)

  • Typical defensive display of a Florida cottonmouth (A. conanti) from north-central Florida (9 April 2011)

References

  1. ↑ McDiarmid RW, Campbell JA, Touré TA (1999). Snake Species of the World: A Taxonomic and Geographic Reference, Volume 1. Washington, District of Columbia: Herpetologists' League. 511 pp. ISBN:1-893777-00-6 (series). ISBN:1-893777-01-4 (volume).
  2. ↑ 2.0 2.1 Ernst CH, Ernst EM (2011). Venomous Reptiles of the United States, Canada, and Northern Mexico, Volume 1: Heloderma, Micruroides, Micrurus, Pelamis, Agkistrodon, Sistrurus. Baltimore: The Johns Hopkins University Press. xviii + 352 pp. ISBN:0-8018-9875-7
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 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. ISBN:0-916984-20-6
  4. ↑ 4.0 4.1 4.2 Campbell JA, Lamar WW (2004). The Venomous Reptiles of the Western Hemisphere. Ithaca and London: Comstock Publishing Associates. 870 pp. 1,500 plates. ISBN:0-8014-4141-2
  5. ↑ 5.0 5.1 Powell R, Conant R, Collins JT (2016). Peterson Field Guide to Reptiles and Amphibians of Eastern and Central North America, Fourth Edition. Boston and New York: Houghton Mifflin Harcourt Publishing Co. xiv + 494 pp., 47 Plates, 207 Figures. ISBN:978-0-544-12997-9
  6. ↑ 6.0 6.1 Crother BI (editor) (2017). Scientific and Standard English Names of Amphibians and Reptiles of North America North of Mexico, with Comments Regarding Confidence in Our Understanding, 8th. edition. SSAR Herpetological Circular 43, 102 pp. (page 59) ISBN:978-1-946681-00-3
  7. ↑ 7.0 7.1 7.2 7.3 Gloyd HK (1969). "Two additional subspecies of North American crotalid snakes, genus Agkistrodon ". Proceedings of the Biological Society of Washington 82: 219-232 .
  8. ↑ Conant R (1969). "A Review of the Water Snakes of the Genus Natrix in Mexico". Bulletin of the American Museum of Natural History 142: 1-140.
  9. ↑ Conant R (1984). "A new subspecies of the pit viper Agkistrodon bilineatus (Reptilia: Viperidae) from Central America". Proceedings of the Biological Society of Washington 97: 135-141.
  10. ↑ Beolens, Bo; Watkins, Michael; Grayson, Michael (2011). The Eponym Dictionary of Reptiles. Baltimore: Johns Hopkins University Press. xiii + 296 pp. ISBN:978-1-4214-0135-5. (Agkistrodon piscivorus conanti, p. 57).
  11. ↑ Parkinson CL, Zamudio KR, Greene HW (2000). "Phylogeography of the pitviper clade Agkistrodon: historical ecology, species status and conservation of cantils". Molecular Ecology 9: 411-420.
  12. ↑ 12.0 12.1 12.2 12.3 Burbrink FT, Guiher TJ (2015). "Considering gene flow when using coalescent methods to delimit lineages of North American pitvipers of the genus Agkistrodon ". Zoological Journal of the Linnean Society 173: 505–526
  13. ↑ Guiher TJ, Burbrink FT (2008). "Demographic and phylogeographic histories of two venomous North American snakes of the genus Agkistrodon ". Molecular Phylogenetics and Evolution 48: 543–553.
  14. ↑ Uetz P, Freed P, Aguilar R, Hošek J (editors) (2021). The Reptile Database, Agkistrodon conanti Gloyd, 1969 (accessed 6 August 2021)
  15. ↑ Mehrtens JM (1987). Living Snakes of the World in Color. New York: Sterling Publishers. 480 pp. ISBN:0-8069-6460-X.
  16. ↑ Conant R, Collins JT (1998). A Field Guide to Reptiles and Amphibians, Eastern and Central North America, Third Edition, Expanded. Peterson Field Guide Series. Boston: Houghton Mifflin Co. xviii + 616 pp. ISBN 0-395-90452-8
  17. ↑ Wright AH, Wright AA (1957). Handbook of Snakes of the United States and Canada. Ithaca and London: Comstock Publishing Associates, a Division of Cornell University Press. 1,105 pp. (in two volumes). ("Cottonmouth, Other common names", p. 916).

Further reading

  • Allen ER, Swindell D (1948). "The cottonmouth moccasin of Florida". Herpetologica 4 (Supplement 1): 1-16.
  • Duellman WE, Schwartz A (1958). "Amphibians and Reptiles of Southern Florida". Bulletin of the Florida State Museum 3: 181-324.
  • Gloyd HK (1969). "Two additional subspecies of North American crotalid snakes, genus Agkistrodon ". Proceedings of the Biological Society of Washington 82: 219-232. (Agkistrodon piscivorus conanti, new subspecies, p. 226).
  • Wright AH, Bishop SC (1915). "A biological reconnaissance of the Okefinokee Swamp in Georgia. 2. Snakes". Proceedings of the Academy of Natural Sciences of Philadelphia 67: 139-192.

External links


Wikidata ☰ Q4692725 entry



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