Myopic little men in tuxedos, or highly efficientland/water animals? Recent research indicatesthere’s more to penguins than meets the eye.
Ifyou’ve every wondered what it would be like tobe able to see as clearly under water as you canon land, just ask the nearest penguin. Most aquaticanimals are short-sighted on land. Most terrestrialanimals (and that includes us) are far-sighted underwater. But researchers have discovered thatpenguins can apparently see equally well in bothenvironments, because of the unique structure oftheir eyes. Penguins have to be able to see wellunder water because their diet consists mainly ofplankton, molluscs, crustaceans, and the inevitablefish.
Through a special slowing-down of their heartrate they’re able, like many other diving animals, tostay submerged long enough to search out andchase whatever catches their fancy. On dry land,it’s a different story-or has been up to now. Waddling along on their flat little feet, eyes fixedintently on the ground, penguins appear myopic,inefficient and generally out of place. In fact thereverse is true. During a recent stay on theFalkland Islands, a Canadian researcherdiscovered that penguins are able to recognizeindividuals and navigate the rocky terrain on whichthey live quite well.
Long of body and short of leg,they probably poke their heads forward as an aidto balance. And as for looking at the ground,they’re merely-like us-keeping an eye on wherethey’re going. The human eye is adapted for aerialvision, which is why scuba divers-or even you andI in the local swimming pool-must wear goggles ora face mask to re-introduce air in front of our eyesin order to see clearly. Among vertebrates ingeneral, the bird eye is frequently described as themost efficient. Its superior quality, combined withthe fact that a large number of birds-cormorants,pelicans, seagulls, even ducks, as well aspenguins-get their food from water, obviouslydeserved research beyond that possible in acontrolled environment such as an aquarium orzoo.
Professor Jacob Sivak of the University ofWaterloo and his associate, Professor HowardHowland of Cornell University, had a chance todo that research recently. Their trip had but onepurpose-to study the structure of penguins’ eyeswhile observing their natural habitat. The FalklandIslands, off the coast of Argentina, offered thisopportunity, being one the few areas outsideAntarctica where penguins can be found in largenumbers. Three of the 16 known species werelocated there: the Gentoo, which live on flat areasright off the beach; the Magellan (also calledJackass), which live in burrows; and theRock-hoppers, which live among the rocks alongthe cliffs. The Rock-hoppers were by far the mostcommon, having a population of well over100,000.
The general rule is, the smaller thepenguin, the meaner the temperament, and theresearchers did witness the odd fight. Theirflippers may look pretty useless out of water, butit’s not smart to play around with a penguin. Hel’llstand his ground in a face-off and if you’re foolishenough to get too close, those flippers can knockyou flat. Dr. Sivak and his associate, however,had little trouble.
Rock-hoppers alwayscongregate in fairly tight groups, as a defenseagainst predatory birds such as the skua (a largeseagull that thinks it’s a hawk), and two moreupright figures in their midst didn’t seem to botherthem. Standing as close to their subjects as 0. 3m,the scientists used two devices: one, developed byProfessor Howland, to take photographs of thepenguins’ eyes; the othger, developed by Dr. Sivak, to shine a series of concentric circles on thecornea and give a measurement of how reflectionsof objects are altered by curvature of the eye. Despite the fact all the work had to be done atnight-the only time the penguins’ pupils weredilated enough-the results were worth it.
Comparison of the photographs with similarphotos of human eyes, and study of the internalstructure of the eyes of creatures discovered killedby seal lions, proved the scientists’ theory that thepenguin’s eyes are the secret of its survival. Ingeneral terms, a penguin eye and a human eye arealmost identical. Both have the same componentsnecessary for vision-a cornea through which lightcan enter; an iris which controls the amount of lightthat enters; and a crystalline lens that focuses thelight onto the back of the eye where a specializedmembrane, the retina, receives it and passes themessage along the optic nerve to the brain forinterpretation. In the penguin eye, hoever, thereare many subtle differences.
The cornea, forexample, is markedly flattened compared to ours– so much so that it almost resembles awindow-pane. This greatly alters the angle atwhich light can enter the eye and is very importantfor underwater swimming, when light enters theeye obliquely through a medium (water) whosedensity is quite different to the density of air. Thepenguin iris is controlled by a very powerfulmuscle which is able to drastically alter the shapeof the lens attached to it, depending on whetherthe penguin is in or out of the water. The lens,comparatively larger than ours and differentlyshaped, focuses the light coming through theflattened cornea onto the retinal body at the backof the eye. In this way, the penguin eye adapts towhatever medium it happens to be in at the time. Interestingly, there was no evidence of eyeproblems (apart from one incident of blindnessdue to injury) in the group of penguins studied.
Ofcourse penguins don’t read, watch TV orencounter any of the numerous irritants weland-bound animals subject ourselves-or aresubjected-to during our lifetime. Both the testingdevices and methods used in this study are easilyadaptable for use with human eyes, paving theway for fast, easy identification of eye problems. Also, the researchers hope that the insights they’vegained into how animals deal with twoenvironments may lead to knowledge of howhumans, in the future, might do likewise.
