Hydrodynastes gigas is a rear-fanged venomous colubrid species found in South America. It is alternatively known as the false water cobra and Brazilian Smooth Snake.[1] No subspecies are currently recognized.[2]

Common namesEdit

Hydrodynastes gigas is commonly referred to as the false water cobra, false cobra, South American water cobra,[1] and Brazilian smooth snake. It is often referred to within the reptile hobby more simply as either a "falsy" or "falsie" or a "FWC", which is an abbreviation of the common name false water cobra. In South America it is sometimes referred to as "Boipevassu".[3]


Hydrodynastes gigas is a large colubrid that may exceed 300 cm (9 to 10 ft) in total length when adult.[1] However most H. gigas reach approximately 2 m (6 to 7 ft) in length.[3][4] H. gigas is of medium body, and is therefore neither particularly heavy nor slender bodied. It is however one of the heaviest colubrid species when full adult size is attained. The common name false water cobra is an allusion to its ability to flatten its neck, similar to a cobra as a defensive reaction to make it look larger and more intimidating.[4] However, unlike the true cobra the false water cobra stays in a horizontal position when it hoods, rather than standing in a vertical position.[5] H. gigas also can flatten not only its neck but also lower down the body, which is not possible for a true cobra.

Additionally, the pattern and coloration of Hydrodynastes superficially resemble those of true water cobras (Boulengerina).

The false water cobra has large eyes with circular pupils allowing good daytime vision. The tongue is black, and of the typical snake fashion.

The background colour of a mature specimen is an olive green or brown, with dark spots and bands covering much of its body.[3] The background coloring and banding generally becomes darker towards the end tail of H. gigas. This colouring gives the false water cobra effective camouflage in its natural rainforest environment. The ventral scales are yellow or brown, spotted with dark flecks that make three dotted lines which appear to merge towards the tail. Mehrtens, 1987, suggested that females are brown ventrally, whilst males are yellow.[3] It has also been suggested that females have lighter bands and markings on the body.[3] This is not an effective way of judging the sex of H. gigas, as coloring will differ slightly between all individuals. Hatchling and juvenile animals are much darker in coloration and do not have the typical dark eyes of the adults. They more resemble a garter or water snake than their mature counterparts. In captivity hypomelanstic animals have been produced. These animals vary in coloration, from some having only slightly lighter colored saddles, all the way to those that are almost patternless.


Geographical rangeEdit

Throughout South America notably Brazil, Bolivia, Paraguay and northern Argentina. There may also be populations living in Colombia and French Guiana.


H. gigas generally lives in wet, humid and marsh land areas.[3] Typically within the tropical rainforests that are common within its range. However, the false water cobra has also been observed in dryer areas,[3] although this is not its preferred habitat. The preference of wet land as a habitat for H. gigas contributes to its common name of false water cobra.


H. gigas is primarily a diurnal species. It is also a very active and inquistive snake, which will spend much of the day climbing, burrowing and even swimming. The temperament of FWCs can vary massively between specimens, some are very docile and reluctant to bite, whilst others are very defensive and even aggressive or intimidating.[3] Captive bred specimens can become quite tame and trusting and many exhibit a high level of intelligence.


In the wild, H. gigas is primarily a fish and amphibian feeder but will take small mammals, birds and even other reptiles. In captivity most are rodent feeders and can quite easily be introduced to other types of food as well.


The posterior maxillary teeth of H. gigas are enlarged and the Duvernoy's gland produces a secretion with high proteolytic activity. Besides the ability of this large and powerful snake to inflict mechanical trauma, there have been numerous cases of local envenomation and perhaps hypersensitivity, most of which have gone unreported. Prolonged chewing bites may result in painful (sometimes extensive and persistent) swelling, as well as bruising.[1] Nevertheless, the species is regularly kept as a pet, becoming increasingly popular in recent years.

Manning et al. (1999) described a case in which an 18-year-old male pet store employee was bitten on the wrist by a specimen that hung on for 1.5 minutes. There was some mild swelling as a result, but after nine hours the victim claims to have experienced three bouts of muscle paralysis, during which he fell and was unable to move or speak. However, a medical examination did not produce any unusual results. It's possible the symptoms described were the result of anxiety.[1]


This species was once considered to constitute a single monotypic genus, Cyclagras [6]


  1. 1.0 1.1 1.2 1.3 1.4 Warrell DA. 2004. Snakebites in Central and South America: Epidemiology, Clinical Features, and Clinical Management. In Campbell JA, Lamar WW. 2004. The Venomous Reptiles of the Western Hemisphere. Comstock Publishing Associates, Ithaca and London. 870 pp. 1500 plates. ISBN 0-8014-4141-2.
  2. Template:ITIS
  3. 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7
  4. 4.0 4.1
  6. Dowling, H.G. & F.W. Gibson. 1970. The relationships of the Neotropical snakes Hydrodynastes bicinctus and Cyclagras gigas. Herpetological Review, 2(2): 37-38.

External linksEdit

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es:Hydrodynastes gigas fr:Hydrodynastes gigas hu:Brazil hamiskobra zh:巴西水王蛇

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