I was terrified of The Magic Tinderbox story as a child. The tale’s soldier hero struck an enchanted match, and instead of a genie, three supernatural dogs appeared to do his bidding. The accompanying illustration of black, shaggy mutts with lips curled back into snarls and ghoulish greenish-white eyes sent shivers down my spine. One dog’s eyes were saucer-sized, the second one’s were the size of dinner plates, while the third had eyes as large as windmills. Had I known of eyeshine, I may not have been so petrified.
Animals active at night need to see in the dark. Their eyes have a reflective membrane, tapetum lucidum, meaning ‘bright tapestry.’ Light enters the dilated pupils and hits the back of the retina where the tapetum is usually located.
The membrane bounces light back to the retina, enhancing the animal’s night vision. It’s this reflected eyeshine that we see blazing back at us.
At Madras Crocodile Bank, Rom showed me how to hold the torch close to my eyes to see crocodile eyeshines. In one of the large enclosures, hundreds of bright unblinking spots glowed in the dark as if planets on the night sky had fallen down. While driving through forest roads in Karnataka and Kerala, I saw the bright eyes of civets, deer, flying squirrels, gaurs, jackals, and dholes.
Frequently, all we see is a pair of bright eyes before the animal vanishes into darkness. Some wildlife specialists claim they can identify the creature just from the colour of eyeshine. Different substances make up the tapetum that may reflect specific colours. In crocodiles, the membrane’s guanine crystals reflect red, cats have riboflavin rods that glow greenish-yellow, while cows and sheep have fibrous collagen that makes their eyes gleam blue.
Dogs’ tapetum is made of zinc cysteine, and my dogs’ eyes reflect blue, green, white, red, or yellow. Tapetum is iridescent, and the colour varies with the animal’s position. That’s why I’m not convinced you can identify animals just by eyeshine colour. Colour and intensity may also depend on whether the torch has halogen or LED bulb.
Ishan Agarwal of the Centre for Ecological Sciences, Bangalore, taught us how to search for small pretty geckos that are well-camouflaged in the leaf litter. The trick is to use a dull incandescent torch that emits yellow light.
In Sri Lanka, Rom and I stayed in a rest house overlooking the large pond of Katagamuwa, Yala National Park. We decided to sleep in the mosquito net-draped beds on the verandah as it was too stuffy inside the room. The ranger accompanying us narrated an incident of how a leopard had mauled someone sleeping in the open.
After nightfall, while Rom spotlit the pond for crocodiles, I scanned the forest for leopards. While he chanted quietly under his breath, “99, 100, 101,” my beam of light picked up little more than spiders that have surprisingly bright eyeshine for their size.
We fell asleep listening to the sounds of the forest: dry leaves rattling in the wind, distant trumpeting of elephants, a rodent or civet scurrying around the roof, the monotonous call of a nightjar, and the sudden startling lapwing scream, “ Didyoudoit ... didyoudoit .”
I woke up in the middle of the night to take a swig of water and scanned the forest with a torch. The brightest pair of eyes, the aura of light as big as saucers, stared back at me. I roused Rom, all my dormant childhood fears making my hair stand on end. His powerful spotlight revealed a leopard. A moment later, the cat disappeared among the trees.
Five years later, a leopard moved into our farm. Every night I scan the perimeter with a torch, while our dogs do their last business of the day in the garden. I feel like that soldier when I switch on the torch. Would the light summon ole saucer eyes?
Ironically, while tapetum allows creatures to see better in darkness, its bright beacon-like reflection gives the animals away.
