Thursday, February 26, 2009

Unusual coloration in Bungarus caeruleus

Bungarus caeruleus (Common Krait) is best known for its ultra toxic venom. A medium-sized member of its genus with a metallic black coloration with white transverse stripes with a white underbelly. Its metallic black color may appear dark blue in certain wavelengths of light it is from this that its Latin specie has been derived. Though it has a bad reputation as a “potential killer”, it is a very peaceful and inoffensive snake, biting only as a last resort. Behavioral differences during day and nighttime is huge in this species. It is quite inert by day and requires a great amount of harassment in order to get it to bite voluntarily. By night it is very active and will make every attempt to avoid a confrontation with human beings. 

Feeds mainly on rodents, frogs and other snakes. The prey is pursued and a lethal dose of venom injected. It is notorious for its appetite for snakes and frequently consumes other snakes including other members of the genus Bungarus. When in pursuit of rodents it often ends up in human dwellings. Also, it is a commonly found species. These characteristics make the Common Krait, most dangerous of Bungarus species. It is one of

 the “Big Four” medicinally important snakes of India. 

Usually, the body colour varies from a dark steely blue-black to a pale faded bluish grey. It is moderately slender. Has a smooth, glossy appearance. It has large hexagonal scales running down its spine, forming a ridge. There are paired narrow white bands along the body. The bands are absent near the neck region. Young specimens may have white spots instead of bands along first one-third of body. 

A rare catch
On 1st September 2006, I got a call from a panicked resident regarding a displaced snake inside his house at around mid-night. On being asked about the size and appearance of the snake, he said “Its about a meter long and whitish in color!” 

I was amazed by the answer. Wasting no time I rushed to the site thinking of a rare specimen. I had no idea what the species might be. On reaching the site, I was stunned by my catch. It was a Common Krait! 

The specimen was so unusually colored that it would be difficult to identify the species for an amateur herper. The dorsal scales were pinkish-white unlike a typical B. caeruleus. The bands were absent through most of its body, the rest were extremely light and hard to spot. The ridge was prominent with larger scales, typical of a B. caeruleus, but was white in color instead of jet black. On getting a closer look, I discovered that the rostral, mental, supralabials, infralabials, nasals, pre-oculars, supraocular and temporals are either fully or partially white. 

I was curious to study such an unusual specimen. Thus the snake was kept in captivity where it behaved rather lethargic and inactive. This was a male measuring 101.6cms. A good size.

In a couple of days, the snake was found to be in a moult. After shedding the skin, it was found active. Also, it started accepting food. Since everything was found to be normal, the snake was released back to a forested area close to the site of capture. 

Can it be a geographical variation? 
Geographical variation has been known in snakes. Snakes are extremely adaptive animals and this feature allows them to live in varied physical conditions. Since they inhabit in varied geographic regions, they develop certain changes in their appearance to adjust and survive in different conditions. For eg. Snakes from colder regions would be rather darker in coloration as they need to consume more heat in the cold conditions.

But in case of this Krait, there is no such explanation. The snake was caught from a moderately populated semi-urban area of Ahmedabad city, where we have been regularly rescuing snakes since atleast past ten years. There has been never such a case. All the snakes of this species in this region are jet black, sometimes bluish black or dark gray, but never pinkish-white, or any similar color. Such a color variation cannot be a geographical variation as there is no data or logical explanation supporting this. 

Color variation? 
In snakes, occurrence of natural color variation is fairly common. This is definitely a case of color variation. But it is not a fulfilling answer as this color is not one of the possible occurrence of colors in a Common Krait. 

Albinism is widely distributed throughout the animal kingdom. It has been found in insects, fish, amphibians, reptiles, birds and mammals. The unusual appearance of albino animals is caused by genetic faults in the metabolic system that produces melanin, a pigment that typically causes the skin to be colored brown through to black. Albinos generally cannot produce melanin and so their appearance is determined by a combination of the other naturally occurring colors in their skin. 

The variation in color was leading to the fact that the body was unable to produce black color where it should have been black. Thus, it may be concluded that this may be a case of partial albinism.

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