Crotalus durissus - South American rattlesnake

English name
South American rattlesnake

Distribution
Crotalus durissus has the largest distribution range of all rattlesnakes, covering all of the South American countries on the main land, except Ecuador and Chili.
C. d. cascavella comes from Brazil and is found in the dry Caatinga region.
C. d. collilineatus found in central and northeastern Brazil.
C. d. cumanensis can be found in Colombia, Venezuela and along the Caribbean coastal plains.
C. d. durissus Guyana, Surinam and French Guiana.
C. d. marajoensis exists only on the savanna of Ilha de Marajo, Brazil.
C. d. maricelae (nomen nudum) exists only in the "Bolsón Arido de Lagunillas", Cordillera de Mérida, Venezuela.
C. d. ruruima found on the slopes of Mount Roraima and Cariman-Peru in Venezuela,Territorio Federal de Roraima in Brazil and possibly extending into southern Guyana and Surinam.
C. d. terrificus starts in southern Peru downward to northern Argentina and southeastern Brazil, passing through Bolivia, Paraguay and northern Uruguay.
C. d. trigonicus found in on the savanna in Rupununi, Guyana and maybe in Roraima Brazil.
C. d. unicolor found only on the island Aruba.
C. d. vegrandis only found in southern Venezuela in the Maturin savanna.

Habitat
The different C. durissus species avoid the dense rainforests but prefer the drier parts of the different countries.

Description
Generally C. durissus is a large rattlesnake reaching lengths of 120cm to 160cm but some populations are dwarfed and don’t tend to go over the 100cm. This species, like C. simus, has a spinal ridge, especially noticeable in the larger adults. The ground color tends to range between brown to red to black, but snakes living in the forest tend to be darker then others. The botches, not always visible, are rhombic or diamond shaped with dark colors at the exterior and lighter/paler color inside and most have a paravertebral stripe starting from the top of their head running down part of the back.

C. d. unicolor inhabits the southeastern part of the island Aruba and lives in a habitat of thorn scrub and rocky desert terrain. They reach an adult length of just a meter. The juveniles of this specie are sharply drawn with an ash-grey ground color and dark blotches but after each shed tend to lose their dark colors and turn into a uniformly ash-gray rattlesnake.

C. d. vegrandis found in an isolated habitat in Venezuela are like C. d. unicolor very different then the other species in the durissus group. In the wild they rarely grow larger then 70cm, but in captivity they can double this length. They tend to have a reddish to brown-black ground color with light white tipped scales, in juveniles these flecks outline the blotches but with age can change enough so no pattern can be seen.

Describing and marking the differences of the other species is almost impossible as the patterns and colors vary tremendously even within the species itself.

Diet
Their diet consists of small mammals and ground dwelling birds available is the regions they live in.

Venom
The venom of the durissus group is as divers as the group it self but the overall effects in humans, of their mainly neurotoxin venom are: nausea, pain, cramps, swelling, damage to skeletal and maybe heart muscle, fever, tubular necrosis but they are also known for their paralysis of muscles of the face and tongue and their venom is know to paralyze the cervical muscles often producing the "broken neck" sign.

Extra
The C. durissus and C. simus group as a whole is still under "investigation" and in the future some will be uplifted into a full species (possibly C. culminates and C. tzabcan) where as others maybe be dropped and merged in one species (like C. d. cascavella and C. d. collilineatus into C. d. terrificus).