Sunday, December 8, 2013

Common Krait : The Mysterious killer in Sri Lanka (තෙල් කරවලා)

In rural dry zone in Sri Lanka, sometimes people die in their sleep or die due to sudden respiratory failure. There is one snake behind all these unknown deaths, it's the most venomous terrestrial snake in the island "The Common Krait" also known as "Magamaruwa"(මගමරුවා) which means DEATH ON THE WAY

Terrestrial kraits belonging to the genus Bungarus of sub family Elapinae and family Elapidae. There are 18 krait species including five sub species are currently recognized by herpetologists and in the snake island of Sri Lanka we encounter two species which is the most venomous among them is the common krait. The scientific name of the common krait is Bungarus Caeruleus. In sinhalese it's known as "තෙල් කරවලා " (Thel Karawala), "මගමරුවා " (magamaruwa), and "හබරලා" (Habarala)


Common Kraits are distributed through out the dry zone and some parts of intermediate zone up to 1600m elevation. It is a nocturnal snake.(All Krait species are nocturnal) rare to be seen in day time as it hides under logs, piles or underground rodent holes or any dark cold place. Slow moving and sluggish during day time. if felt threatened it coils up and hide it's head inside the coil and wiggle it's tail as a distraction. but totally different story at night. they are very active and could be aggressive if provoked.

Kraits are easy to identified thanks to the large hexagonal vertebral scales and coloration. same conditions applies to the common krait. Dorsal coloration of the common krait ranges from black to bluish black, purple tint black and sometimes brownish black with 20-25 white band pairs on dorsal body. These white bands are usually paired. juvenile common kraits have bright milky white bands all over their body. Head is indistinct from the body and depressed, looks cylindrical from head to tail. It has a red color tongue and small black round pupiled eyes.



                                                                Image Credit - Prathamesh Ghadekal

30 to 42 undivided sub caudal scales, 195- 208 ventral scales and 15 mid body scale raws are present in common kraits body.


                                                    Juvenile Common Krait- Image Credit- Hemant Ogale

As you can see in the images above they have a shiny smooth scales like it's been oiled up. This is why Sri Lankans used to call it Thel Karawala which means Oil Krait. Along with shedding and growing the milky white bands gets disappeared.

Common kraits mainly feeds on other snakes including blind snakes and baby cobras and shows cannibalism as well by eating their own kind. frogs, small mammals and lizards are part of the diet.

                                      A Common Krait Feeds on a Wolf Snake- Image Credit to Vivek Sharma

Bungarus Caeruleus is an oviparous snake. They mate in 3rd and 4th quarter of the year and female lays 6 to 10 eggs measuring around 35x19mm. Females will guard their eggs around 60 days until hatchlings comes out. Hatchlings are about 11 inches and they grow to an average length of 3 feet. Reports says some specimen grow up to 5 feet as well.

Talking about the venom, kraits have neurotoxins and the potency of venom varies species to species. common krait is equipped with short fixed proteroglyph fangs on their upper jaw capable of delivering one of highly potent snake venom in the world. Common krait has both pre-synaptic and post-synaptic nuerotoxins which attacks your nerve system, destroying communications between brain neuron cells and muscles and turning the victim to in to paralyze. lethal dose of venom to humans are 1mg and a common krait delivers up to 20mg of venom in a single bite. It is 16 times venomous than cobra venom. after a krait bite the victim has only 10-12 hours to live without treatments. Color of the common krait venom is amber.

So why it's known as a silent mysterious killer? The main reason is common kraits enter human habitations at nights when people are sleeping. in rural areas people often sleep on the floor. This is a perfect warm place to a krait to coil up. once the sleeping human change his sleeping position or do any other move krait gets threatened and bites the sleeping human. Krait bites are painless and no bite marks can be seen to naked eye. small children usually dies in their sleep if a krait bite happens. By the dawn it moves again to a hiding place without a trace. after awaken, people feel abdominal cramps and muscle paralysis. If not treated, the victim will lose his life. Mortality rate of a common krait bite is 70-80% without anti venom. Some medical reports says it's 50% even with anti venom. That is why people in south Asian sub continent should be extra cautious when walking outside at nights. If you step on this type of krait, Death is on the way! you may not feel the bite. It's quite painless. According to the world famous herpetologist Austin Stevens, Kraits are like to hang on to their victim for few seconds so they can inject venom effectively. If you getting bitten by any kind of krait, best thing to do is pull it off quickly from the bitten area. More it hangs on to you more venom will be injected.

Symptoms of a Common Krait Bite

*Abdominal pain
*unconsciousness and muscle paralysis
*Bite mark mostly not seen,
*Local swelling rarely found,
*Body weakness,
*Drooping of eyelids,
*Difficulty in respiration,
*Respiratory arrest,
*Cardiac arrest,

It's also important to talk about wolfs snake (radhanakaya) because it's familiar looking as a krait. People often kills these innocent non venomous colubrid snakes by misunderstanding.

                                                                    Wolf Snake (radhanakaya)

The best way to differentiate a wolf snake from a krait is by looking at it's head and scales. Wolf snakes head is larger and it's distinct from the body. The vertebral scales are similar to the mid body scales and have wide white bands which are not paired. So once you see a krait like snake watch it twice before relocating.

Myths about Common Krait

It's surprising to see no myths about this snake among Sri Lankan people. But there is a myth coming from India. people believes this snake come to lick human sweat and it will just lick you without biting. the lick from this snake will led to a silent death.
It's quite obvious why people believe in such a myth. Krait bite marks are not visible to naked eye. so people judge it by tongue.

Here is a video of a Common Krait in Sri Lanka.



Common krait is the most venomous terrestrial snake in India as well. even you are a good snake handler it's important to take extreme caution when handling a krait. A mili second mistake may cause your life in trouble. They are very important for us for making anti venom so please don't kill these snakes if you encounter one

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