Distinctly Montana Magazine

d i s t i n c t ly m o n ta n a • s u m m e r 2 0 1 5 26 are what allow humans to see color, but because many nocturnal animals lack cones, their color vision is poor or absent. Nocturnal vision is less sharp than day time vision. To compensate for poor visual acuity, the eyes of nocturnal animals, like the flying squirrel, are large for their body size. Owls have some of the largest eyes of any nocturnal animal. If a great horned owl was the size of a human, their eyes would be as big as oranges. Because of the size and shape of their eyes, owls can't rotate their eyes like we can. Instead, owls have the amazing ability to turn their heads more than 180 degrees to look in any direction. Nocturnal animals have another unique ad- aptation for helping them see in the dark. Have you ever noticed how a deer or coyote's eyes shine in headlights? e eyes of some animals appear to glow because of a layer of mirror-like cells located beneath the retina called a tapetum lucidum, which means "bright tapestry." e tapetum reflects light back through the eye. is recycling of light helps animals make the most of dim conditions. Different species' eyes shine different colors. Deer's eyes shine yellow while coyotes' eyes shine green-gold. Black tailed jackrabbits' eyes shine red and foxes' eyes shine white. ese color variations are caused by differences in the amount of minerals that make up the tapetum. e colors also vary within a species based on factors like age. But there are other nocturnal adaptations beyond keen eyesight. For example, foxes, which are primarily nocturnal, have exceptional hearing. Foxes can hear a squeaking mouse from 100 feet away. eir long whiskers help them sense their environment in low light. Like foxes, owls also rely on their keen sense of hearing to locate prey. Great horned owls are Montana's most common owl species. ey live in a variety of habitats from deep in the forest to your backyard. Great horned owls get their name for the two earlike tufts on their heads. ese tufts of feathers have nothing to do with hearing. Instead, they serve to camouflage the owl while it roosts during the day. Like all owls, great horned owls have asym- metric ears. With one ear located higher than the other, they're able to determine whether a mouse or vole is above or below them based on the time it took for the sound to reach each ear. An owl's sensitive hearing is enhanced by their facial ruff. e ruff is a concave surface of stiff feathers that frames their face and acts like a reflector to channel sounds to their ears. When an owl has finally located its prey, they The eyes of some animals appear to glow BECauSE OF a layEr OF mirrOr-liKE CEllS lOCaTED BENEaTH THE rETiNa WHiCH rEFlECTS ligHT BaCK THrOugH THE EyE. THiS rECyCliNg OF ligHT HElpS aNimalS maKE THE mOST OF Dim CONDiTiONS. NeAL HerBerT/NATiONAL pArk ServiCe For another article by this author, see: "Hibernation or Migration?" Winter 2015 DISTINCTLY MONTANA | DIGITAL Montana's Wild Nightlife

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