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False Water Cobras (Cyclagras (Hydronastes) gigas)
The care of False Water Cobras (Cyclagras (Hydronastes) gigas). By Kevin Stevens. Originally publised in The Herptile, journal of the International Herpetological Society

This article is intended to enlighten the reader with regards to this wonderful species, both its pros and cons as a captive subject, some brief natural history and notes on successful reproduction stimuli. I had hoped to track down some, what have turned out to be quite elusive, papers pertaining to this species. I hope the reader (and the authors of the missing papers) can forgive me in that I would like to use some of the details from memory but cannot give any references.

A species that has always intrigued myself, and many other amateur herpetologists, is the False Water Cobra. In its native South America it is sometimes referred to as “Boipevassu” (Friend, 1989) and has also been given the common name of the Brazilian Smooth snake (Mehrtens 1987). Firstly described in 1854 by Dumeril, Bibron and Dumeril, and placed in the genus Cyclagras (the only species within the genera) by Cope in 1885. Often referred to as Hydronastes gigas. Various workers have varying opinions with regards to
False Water Cobra Hydronastes gigas
False Water Cobra Hydronastes gigas
this species – the confusion appears to be centred around three species Cyclagras gigas, Hydronastes bicinctus and Hydronastes schultzi. Many modern studies have made the decision to make Cyclagras defunct and replace with Hydronastes, a genera with two species – H. gigas and H. bicinctus. This author still maintains the original description

Natural History
Confined to South America, including (but not exclusively) Bolivia, Paraguay, Brazil and northern Argentina. Other areas could include French Guiana and Columbia. Usually encountered around wet land and marsh areas, but does occur in dryer areas. It is said that the diet in the wild consists of frogs, fish, reptiles small mammals and birds. A medium to large sized snake, reaching around two metres in length. Colour is variable, olive green or golden brown is common, usually with irregular dark coloured crossbands and spots. Ventrally they are often yellowish or brownish with dark flecks and speckles. Mehrtens, 1987, states that males are ventrally yellow coloured, females are brown. Coburn, 1991, also makes a reference to females having lighter markings, presumably both ventrally and dorsally. I have personally seen males and females coloured the same. Although their cobra impression of raising their bodies and flattening the neck when “hooding up” is impressive, it is by no stretch of the imagination very comparable to the display given by Naja species.

The False Water Cobra is a rear fanged venomous species. Currently (May 2000) there are no restrictions regarding keeping them in captivity in the U.K.. They are not a species covered by the Dangerous Wild Animal Act 1976. It would appear (though not necessarily the opinion of this author) that this may change in the future as more studies show the true nature of the venom and the venom delivery capability of this species. May I refer the reader to the Mangrove snake (Boiga dendrophilia), a species often seen in the pet trade up until it was discovered that they were potentially more dangerous than first thought and placed on the Dangerous Wild Animal Licence. From discussions with Paul Rowley at Liverpool School of Tropical Medicines it would appear that recent studies have likened the potency of the venom to the Timber Rattlesnake, Crotalus horridus. I personally have only seen the results from one bad reaction from a False Water Cobra bite. The late John Foden was unfortunate to receive a bite from an adult on his arm. He told me he thought little of it at the time, until the arm swelled dramatically. Within a couple of hours he felt very poorly with a fever and severe nausea. Over the following days tissue damage occurred around the area of the bite, and a feeling of being generally unwell lasted for several days. Some time later he still complained of discomfort, and was left permanently with a disfigured arm. Needless to say that my keepers and myself treat these snakes with respect as if they were a “venomous” species and only handle with gauntlets and /or a hook. Temperament can vary from gentle and placid to violent and intimidating.

Captive care and breeding
In 1997 several False Water Cobras were in my care in the breeding facilities at Coast to Coast Exotics. At the time we had 5 males and three females of various ages from around 18 months to 17 years old. The main breeding attempts were with the older animals. Two pairs of these older snakes where housed in vivaria in our tropical room along with several species of tropical and sub-tropical boas, pythons and chelonia. Each pair were housed in their own 1.5mx0.6mx0.6m melamine constructed vivarium. Entrance into these vivaria was through twin (locked) toughened glass doors. Ample ventilation was provided from vents in the back and sides of each vivarium. Heating was provided by heat mats placed on the floor - no more than one third of the floor area was heated. Thermostats controlled the temperature during the day to provide a warm end temperature of about 30°C, at night the mats were switched off allowing the temperature to drop to the ambient 25°C of the tropical room. Furnishings included a cork bark hide, a large water bowl for soaking and a floor covering of orchid bark. The choice of furnishings allowed us to provide a medium to high level of humidity within the vivaria. Both the cork bark and the orchid bark maintain moisture very well and were kept mildly damp with a regular spray with tepid water. The humidity level in the tropical room was rarely below 80%. The pairs were only separated for feeding.

During the winter of 1997-98 mating was noted, but no eggs were consequently laid. Mating has never been regularly seen during the summer months. Winter 1998-99 saw our first serious breeding attempt. We decided to cycle them similarly to many of our Boids. The temperature was lowered to around 28°C during the day, dropping to a low of about 18-20°C at night. Spraying with tepid water was increased in the hope of simulating a “rainy season”. At first very little mating activity was noted in either pair, but after three or four weeks of these conditions mating was often and very vigorous. It is fair to say that the males give the females very little in the way of rest, but it appears that the females are just as insatiable. Copulation is of the typical snake affair, the male stimulates the females body with his own with rapid movements and twitching, the female responds with similar twitching – the whole act taking any where from a few minutes to hours. This continued for many weeks, to the point that one would believe that the female would never conceive. Some seven weeks passed from the initial copulation the younger female sloughed her skin. Upon examination she appeared gravid so an egg laying box was placed in the vivarium. This consisted of a cat carrying box full of wet sphagnum moss. The male was separated. Many snake species lay their eggs around ten days after sloughing their skin (known as the pre-lay slough). Some sixteen days later I was concerned that she had become egg bound. Fortunately I resisted the temptation to intervene and she laid a clutch of seventeen eggs naturally without inducement a further three days later. The older female (at a grand old age of at around 17) did not reproduce, and was later “retired” from the breeding group. The clutch of eggs were removed from the vivarium, placed into a large plastic container quarter filled with vermiculite and moved into our large walk in incubator. During the incubation temperatures were kept at a more or less constant 29°C. Humidity varied from around 80% to almost 100%. Maintained in these conditions they began hatching after 65 days, within two days all seventeen hatched successfully. The hatchlings were housed in typical methods on a heated rack system. Seven did not feed at all, the others accepted food readily. Scent manipulation with fish seemed to work with the fussy feeders, leaving only two stubbornly not feeding. Some seven weeks later a mystery spate of deaths led to losing six hatchlings, no signs of ill health were noted and all but one was feeding. A faecal and blood sample from the dead babies was sent to our pathological laboratories but all came clear. We have had no further deaths and cannot account for losing these six hatchlings within days of each other.

The following summer saw us returning the adults to their original conditions. It was decided to “cut out some of the dead wood” in the collection and stream-lined the group to one male and two females. A decision to move all of our heavy bodied snakes (mainly Boids) away from under floor heating (i.e. heat mats) was taken. This was replaced with ceramic heaters mounted in the roof of the vivarium. This was decided due to our accumulation of evidence to suggest a link with under floor heating and necrotic dermatitis – a rotting condition of the ventral scales. This coincided with a major re-fit at our premises allowing us to display some of our breeding stock to the general public. The three remaining cobras are now housed separately in wood vivariums measuring 1.4mx0.7x0.7m in the same conditions described earlier. The only difference is the provision of artificial lighting with full spectrum fluorescent tubes so that visitors can see them better. None seem in the least bit bothered by the increase in human disturbance from the viewing public. During the winter of 1999/2000 the same cycling methods were employed. The male was swapped from one female’s vivarium to the other. A similar pattern ensued, resulting in both females laying sixteen eggs each. Again, nearly twenty days passed after the pre-lay slough before either females laid her eggs. Presently (May 2000) the clutches of eggs are three and four weeks into incubation and all look healthy.

Thank you
Thanks go to Sue Patterson at Rep-tech, Windsor, England for providing some of the breeding stock mentioned in this article, including the “old girl” we later retired.

A parting thought
I would like to take this opportunity to dedicate this article in the memory of John Foden, who died recently. Although I was not one of his closest friends I feel privileged to have known him at all. A rare character in the reptile world, always with a tale to tell, a witty remark or humorous comment to make, an opinion to share and an unrivalled love and knowledge for all animals. Missed but never forgotten.

Coburn, J. 1991. The Atlas of snakes of the world. TFH Publications, Neptune City, USA.
Friend, J & C, 1989. Captive breeding of the False Water Cobra, Hydronastes gigas. The Herptile. Volume 14, Number 3, page 122. Journal of the International Herpetological Society, England.
Mattison, C. 1995. Encyclopedia of snakes. Blandford Press, London, England.
Mehrtens, J.M. 1987. Living snakes of the world. Sterling Publishing Co. Inc, New York, USA
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