That Reptile Blog – Reptile, Amphibian and Exotic Pet Care and Information

The 60+ species of sea snakes – brightly colored, highly venomous relatives of the cobras, mambas and coral snakes – are little studied and not often seen in zoos.  I was fortunate enough to have worked with yellow-bellied sea snakes (Pelamis platurus) at the Bronx Zoo, but the species is no longer exhibited there (perhaps something to do with the preferred diet of live moray and American eels?).   If you have the opportunity to visit a zoo that keeps sea snakes, by all means do so – you will not be disappointed.

How Marine Snakes Find Fresh Water

A recent Physiological and Biochemical Zoology article, written by noted herpetologist Harvey Lillywhite, dispels a popular belief concerning marine snakes.   Sea snakes, it seems, do not use special glands to extract salt from sea water, thus rendering it drinkable.  These glands remove excess salt from the bloodstream, but the snakes can drink only fresh or very dilute sea water.

Research focusing on the black-banded sea krait (Laticauda semifasciata) showed that the snakes obtain all their drinking water from fresh water springs (sea kraits leave the water on occasion), and refuse to drink sea water even when dehydrated.  The majority of other sea snakes, which do not travel overland, are presumed to drink from the surface layer of fresh water that develops on the ocean when it rains.  Indeed, sea snakes reach their greatest diversity in regions with heavy rainfall, and sea kraits are most common near fresh water spring outflows.

Notes on Marine Reptiles in North America

The study seems to raise questions as to the drinking habits of other marine reptiles, such as sea turtles.  It brought to my mind time spent observing mangrove salt marsh snakes (Nerodia clarkii compressicauda) in Florida – that particular snake lives largely in salt water, but periodically travels to nearby fresh water swamps to drink.

At the mouth of the Nissequogue River on Long Island, NY, I encountered a population of snapping turtles (Chelydra serpentina) that have been documented as having salt-excreting glands not possessed by snapping turtles living further upstream in the same river.  I’ll soon review an article written on the turtles in that habitat, with a view towards reconciling it with this surprising new information.

You can read more about the natural history of sea snakes and sea kraits at the web site of the Chicago Field Museum:

http://www.fieldmuseum.org/aquaticsnakes/true_sea.html

Image referenced at Wikipedia, http://en.wikipedia.org/wiki/Image:Banded_Sea_Snake-jonhanson.jpg, and originally posted by Jon Hanson on FlickR.

It is often difficult to determine what a snake will do in a particular situation, as their external cues are quite subtle. A great deal is going on behind those unblinking eyes, I can assure you, but most species give us little to go on. Not so, however, with the cobras – active, alert and intelligent, their behaviors are much more evident to us.

Among professional herpetologists, the king cobra has the reputation of having all the aforementioned cobra qualities in excess. This, combined with a length of up to 18 feet (it is the longest of the venomous snakes) renders the king cobra among the world’s most formidable animals.

Those I worked with at the Bronx and Staten Island Zoos invariably watched and reacted to each of my movements instantly, in almost “mammalian” fashion. The doors to snake exhibits are equipped with metal panes that can be slid open to reveal a small window, thus allowing the keeper a look inside. Nearly always, king cobras respond to the pane’s movement immediately by rearing up and peering back through the window – quite unnerving the first time it happens to one! No other snake has responded in this way in all my many years of working in zoos.

So it was with some trepidation that I responded to a call from an airport official who claimed that a “giant” cobra (escaped snakes are always “giants”!) had escaped from its shipping crate (I have agreed not to reveal the identity of the airport). Fortunately, the animal was contained with a small, relatively bare room. Armed with a pair of tongs and a garbage can lid, I entered, thoughts of Frank Buck’s similar story, related in his classic book “Bring ‘Em Back Alive,” bouncing about in my mind.

The snake, about 9 feet long, reared up in typical cobra fashion and, its head at my waist level, advanced. I have been in my share of tussles with wild animals, but the phrase “Discretion is the better part of valor” never rang truer. I backed out and asked for a secure box with a hole cut in one side. I pushed this into the room and, as I had hoped, the cobra darted inside – for once the species’ alertness working in my favor. The lack of cover in the room had strengthened its will to fight – provided with a way out, the snake retreated. I was able to secure it without incident.

A group of NYC police officers had gathered outside the room. The younger ones were quite disappointed that I had not leapt upon the snake and subdued it with a grasp to the neck. The oldest officer, the sergeant in charge, simply said “Thanks for sparing me a wild ride to the hospital and a ton of paperwork”!

One of my fondest “reptilian” memories is of snake hunting with famed herpetologist Romulus Whitaker.

Captive Breeding – my experience
The king cobra’s taste for other snakes complicates breeding efforts in zoos. During my years as a zoo keeper I experienced several successes and failures. I once housed a pair in adjoining exhibits, separated by a screen panel, for 3 months in order to gauge their reactions to each other. They seemed to get along well and, indeed, co-habited peacefully for several weeks. Always well fed, there were no signs of aggression. Unfortunately, however, there was also no sign of the female one morning – the 12 foot long male had swallowed all 8 feet of her – quite a feat even for a snake!

Working With King Cobras
Although rumored to be aggressive in nature, king cobras often (but not always!) flee when confronted by humans if given the opportunity. Captives are, however, extremely alert and seem, at least upon casual observation, to evince learning abilities not possessed by other snakes. I have always preferred to house them in exhibits equipped with shift cages, into which the snake may be secured before I entered the exhibit – they are just too fast to work with close at hand (my predecessors at the Bronx Zoo seemed to feel likewise – in an old storage area I came across an old wooden “cobra shield” – I like to think it may have been used by the eminent Raymond Ditmars, first reptile curator at the Bronx Zoo). When shifts are not available, I exercise extreme caution and, as with all venomous snakes, alert co-workers of my whereabouts.

King cobras are notorious escape artists, even for snakes, and the cause of much lost sleep in the zoo world. Some years ago a major zoo was closed down for 3 days while an escaped specimen was at large (it was, luckily, re-captured without incident). I’ll relate my own experience with 3 escaped spitting cobras in a future article.

Cobra Classification and Venom
King cobras and the 300 or so other members of the family Elapidae are known as “Proteroglyphous Snakes” – a term referring to the fact that their hollow, venom conducting teeth (fangs) are fixed in position and cannot be erected as can those of the vipers and their relatives (the Solenoglyphus Snakes).

Cobras inject venom by biting and employing a chewing motion, and cannot utilize the stab and release action of the vipers. The venom of most species is highly effective, and large specimens can deliver huge quantities of venom in a single bite. It is often said that an adult king cobra may carry enough venom to “kill a small elephant” – while that is difficult to quantify, a cobra of any species is a most dangerous animal.

Other Cobras and Their Relatives
Elapids reach their greatest diversity in Australia, dominating the snake fauna there. There are over 50 species in the Americas, with coral snakes being the only representatives found in the USA. Arboreal, aquatic and burrowing forms occur in Africa and Asia. Several African cobras can eject venom at the eyes of enemies (they hunt in usual cobra fashion), an adaptation to life in grasslands populated by large hoofed mammals. Sea snakes, kraits and mambas are related to cobras and also classified as Elapids.

The Cobras’ Hood
The defensive display of cobras involves rearing up and flaring out a wide hood of skin about the head and upper body. This is accomplished by raising a series of elongated ribs, which in turn stretch the skin between them to form the hood. A large king cobra may raise over 4 feet of its body from the ground when agitated – a most impressive (and convincing!) display.

Information concerning king cobras in India is posted at:
http://www.india-wildlife-tours.com/wild-animals-in-india/indian-wildlife-king-cobra.html

Physical Description
The king cobra is the world’s longest venomous snake, and may exceed 18 feet in length (average length is 12-15 feet).

Its color and pattern varies greatly across the huge range, with unique color morphs being distinctive of certain geographic areas: specimens from Southeast Asia are usually a uniform olive or yellowish-olive in color, while those originating in India tend to be olive with yellow bands and a black tail. Chinese specimens are often dark brown or black, and banded with white, brown or yellow.

Range and Habitat
This snake’s enormous range extends from northern India through Myanmar, Bangladesh and Cambodia to southeastern China (including Hong Kong and Hainan) and south through Laos, Thailand, Vietnam and much of Indonesia (Sumatra, Java, Borneo, Sulawesi) to western Malaysia and the Philippines.

King cobras occupy a wide variety of habitats but are usually found near a permanent water source. They occur in rainforests, dry forests, lightly wooded areas, overgrown fields, bamboo thickets, mangrove swamps, agricultural areas and along the outskirts of towns.

Status in the Wild
Not well studied. King cobras adapt to some disturbance and often frequent farms in search of other snakes (the favored prey) that are drawn there by rodents. Listed on Appendix II of CITES.

Diet
The king cobra feeds almost exclusively upon other snakes, although lizards are occasionally taken (the Greek-derived Genus name means “Snake-eater”). It hunts by day and actively searches for prey. Keen sighted and quick, king cobras are well-suited to pursuing fast-moving snakes.

In zoos, hatchlings and wild-caught adults often refuse all but snakes as food. Reptile keepers resolve this problem by “scenting” mice and rats (the snakes thrive on a rodent-based diet) with dead snakes that are kept frozen for this purpose. Usually, rubbing a snake on the rodent does the trick. Particularly choosy cobras sometimes force us to become resourceful – boiling a piece of an expired snake in water and soaking the rodent therein is the standard method used in these cases. Most king cobras can eventually be weaned onto a diet of non-scented rodents.

“Scenting” is used to induce other serpentine food specialists to accept alien food items as well. Eastern hog nosed snakes, Heterodon platirhinos, for example, are confirmed toad-eaters but eagerly take toad-scented mice.

Reproduction
King cobras are the only snakes known to construct a nest for their eggs. Using loops of her body, the female scrapes together a pile of rotting leaves and other vegetation, into which the eggs are deposited. Some construct a two-chambered nest, with the upper chamber serving as retreat for the female, while others merely coil on top of the leaf pile.

The female guards her 20-60 eggs for the 60-80 day incubation period. There is some evidence of mate fidelity that the male may also remain in the vicinity of the nest, but this has not been accurately documented.

The hatchlings are 18-22 inches in length and differ markedly from the adults, being boldly striped in black and white.