Wildlife of Pakistan - Otter Specialist Group

Volume 1: Issue 1: January - March, 2012VisionSaw-scaled Viper (Echis carinatus) © Syed Shamim Fakhri, ZSDfades and finishes with the deathof the outer cells of the skin. Thesnake becomes passive for a weekor two. The dead skin is removedby expanding and contracting thebody. The snake opens and closesits mouth and rubs its body tohard any surface. First the skin isremoved from the head. Suddenlythe vision becomes sharp as thedull eye covering is removed. Withthat the snake becomes agile andthe dead skin is peeled off inside outfrom head to tail. Bright and glossycolour pattern of the body appearsagain. The snake becomes againactive for hunting. The first removalof the dead outer skin takes placein early part of the life when bodygrowth rate is faster. This occurs infirst one week or so after hatching.Afterwards the dead skin is removedwith the growth of the body once,twice or even three times during thesummer season.Snakes have no external earsA snake has no external and middleear. So it cannot hear. However, asthe bones of the middle ear havebecome connected with jaw bonewhich are normally attached tothe ear drum. As the under part ofthe head and the body are directlyplaced on ground any vibration fromany movement or scratching on theground nearby is communicatedfrom the lower jaw to the brainthrough the auditory nerve whichis connected to the internal ear. If asnake happens to be lying on a floor,any music or sound will not affect it.But if a chair is dragged on the floorthe snake will respond immediatelyby its body movement. Swaying ofCobra with the snake charmer’s fluteis not because the cobra has enjoyedthe music. The snake charmer firstprovokes the cobra in his basket.The excited snake expands its hoodand exhales loudly, at the sametime darts its head forward to bluffand frighten away the provoker. Asthe sensitive ventral plates belowthe neck receive sound waves ofthe flute the upset snake focuses itsattention on to the flute.It moves its head as the snakecharmer sways the flute.Eyes are placed on the sides of thehead, so these can see on bothsides, but both are unable to focuson an object together like we do.Each eye has its own independentfocusing. Snake makes its lensto move forward or backward tofocus. Snake’s lenses are yellowwhich helps in night vision. Its eyesight is not sharp. It can detectmoving creatures, however, thingsnot moving become difficult torecognize, unless they are closeenough to be felt by their heat.Body temperatureThe body temperature of snakerises or decreases with the riseor decrease of surroundingtemperature. In winter days, as theatmospheric temperature lowers, thesnakes cannot remain active as theirbody temperature also decreases.They look for some shelter from coldtemperatures of the night in someburrow or heap of dead leaves.They remain passive in that placefor the winter months. The bodyneeds much less energy. However,even slow functioning of the bodysystems some energy is consumed.This energy is transferred frombody fat. In late spring or earlysummer with the rise of atmospherictemperature their body temperaturealso rises. The snakes come outof their wintering places to look forfood as their body has no fat.Poisonous or Non poisonousMajority snakes found in Pakistanare non-venomous. Only threecategories are venomous. Thesecategories are Cobra, Krait andVipers. The basic difference inpoisonous snakes is that these injectWILDLIFE OF PAKISTAN9