Crotalus durissus

''Crotalus durissus'', known as the South American rattlesnake, tropical rattlesnake,Mehrtens JM. 1987. Living Snakes of the World in Color. New York: Sterling Publishers. 480 pp. and by other names, is a highly venomous pit viper species found in South America. It is the most widely distributed member of its genus. Currently, seven subspecies are recognized.

Taxonomy

The Guiana rattlesnake, previously recognized as ''C. d. dryinus'', is now considered a synonym for ''C. d. durissus''. In fact, after the previous nominate subspecies for the ''C. d. durissus'' complex became the current nominate for ''Crotalus simus'', which now represents its Mexican and Central American members, ''C. d. dryinus'' became the new nominate for the South American rattlesnakes as represented by ''C. durissus''. The subspecies previously known as ''C. d. collilineatus'' and ''C. d. cascavella'' were moved to the synonymy of ''C. d. terrificus'' following the publication of a paper by Wüster ''et al.'' in 2005.

Subspecies

Description

A large Neotropical rattlesnake, it grows to a length of , and rarely to a maximum length of . It has two distinct stripes starting at the base of the head. Within the lines, the color is lighter than the stripes.

The color and pattern of the body are quite variable, most with an 18–32 dorsal with a darker diamond, and rhombic spots, 25–33 (usually 27) rows of dorsal scale in the middle of the body. The head has a dark brown bar at the top, with a dark post-orbital band. The color of the belly varies, it can be white or yellowish, with light gray spots, becoming darker towards the tail. The tail is usually gray, with dark and vague crossed bands.

Behaviour

The species is more active at dusk and in the early hours of the morning; it is usually not aggressive towards humans, but can bite if cornered or threatened.

Reproduction

The South American rattlesnake has a seasonal reproductive cycle; competition between males (for access to females) begins around the summer's end, with copulation occurring during the fall, and the birth of the young taking place the following spring/summer. Reproduction is ovoviviparous, giving birth to 4–8 young. In Roraima, Brazil it has been reported that the gestation lasts for 5 months, and they are capable of giving birth to up to 14 young.

Diet

The diet consists mainly of rodents, likely due to the great abundance and availability of these animals throughout the year, in most areas where the snakes reside. In some regions, lizards of the Teiidae family are also part of the diet of ''C. durissus''.

Common names

Common names for the species include: South American rattlesnake, tropical rattler, tropical rattlesnake, neotropical rattlesnake,U.S. Navy. 1991. Poisonous Snakes of the World. US Govt. New York: Dover Publications Inc. 203 pp. Guiana rattlesnake (previously used for ''C. d. dryinus'').Brown JH. 1973. Toxicology and Pharmacology of Venoms from Poisonous Snakes. Springfield, Illinois: Charles C. Thomas. 184 pp. LCCCN 73-229. and in Spanish: ''víbora de cascabel, cascabel, cascabela'', and also in Portuguese, ''cascavel''. In Suriname it is known as Sakasneki.

Geographic range

''Crotalus durissus'' is found in South America except the Andes Mountains. However, its range is discontinuous, with many isolated populations in northern South America, including Colombia, Venezuela, Guyana, Suriname, French Guiana and northern Brazil. It occurs in Colombia and eastern Brazil to southeastern Peru, Bolivia, Paraguay, Uruguay, and northern Argentina ( Catamarca, Córdoba, Corrientes, Chaco, Entre Rios, Formosa, La Pampa, La Rioja, Mendoza, Misiones, San Juan, San Luis, Santa Fe, Santiago del Estero and Tucumán). It also occurs on some islands in the Caribbean, including Aruba. The type locality given is "America."

Habitat

It prefers savanna and semi-arid zones. It has been reported to occur in littoral xerophilous scrub, psammophilous and halophilous littoral grassland, thorny xerophilous scrub, tropophilous deciduous and semideciduous scrub, as well as tropophilous semideciduous seasonal forest in the northwest of Venezuela