Nocturnal naturalists explore fascinating world

By Gary Raham
Nature Writer and Illustrator

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I once wrote about a child on a camping trip who was afraid of all the night-time noises until she learned to recognize them for what they were: the songs of night creatures. Eventually she came to anticipate and enjoy the night. I would urge everyone to turn off "Survivor" on occasion and explore their yards and gardens for the fascinating night folk you will find there.

Although we humans specialize in daylight activity, we have enough black and white receptors in our eyes (rods) to see pretty well with a little dark adaptation. It takes 15 minutes for the shutter in your eye (the iris) to open maximally and about 30 to 40 minutes for the light-sensitive retina to become fully adjusted. Because the color sensors (cones) dominate the center of the retina, and the rods reside near the periphery, it's easier to see objects at night by looking out of the corner of your eye.

You can maintain good night vision - as long as you can avoid street or yard lights - by lighting your path with a red flashlight. These can be purchased or you can convert any flashlight by covering the lens with red cellophane. Many nocturnal mammals have mostly rods in their eyes, so they are red blind. Many insects can't see red (although they often see beyond our rainbow into the ultraviolet). Fishermen know that earthworms are best collected from moist garden soil using such a red flashlight. Amateur astronomers use red lights to record their observations of stars, comets and other celestial events.

On warm spring nights following rainy days you may be lucky enough to see migrations of toads and salamanders as they move downhill toward moisture. I've had tiger salamanders - the only salamanders native to Colorado - find themselves stranded in my window wells after gully-washing rains.

On the other hand, regular flashlights may reveal the identity of certain creatures of the evening. Everyone recognizes a cat's eyes transfixed by headlights. A mirror-like membrane in their eyes called the tapetum reflects light back toward the retina and, inadvertently, to the motorist.

An experienced naturalist can often recognize an animal by the color of its eyes at night. A raccoon's eyes shine bright yellow. Dogs and foxes reveal bright white eyes fairly close to the ground, whereas a deer's eyes are white and several feet above the ground. A bobcat's eyes glow yellowish white; a skunk's are amber. An opossum's eyes burn dull orange and a night heron displays red to red-orange eyes. Tiny white specks in the grass are probably the eyes of wolf spiders out for a stroll.

Moths visit the white or light-colored flowers in your garden. Milkweed flowers attract bees and beetles by day and moths at night. In the southwest, bats often pollinate cactus and agave.

Entomologists wishing to view night-flying insects know that blue light or white light (especially when focused on a sheet) attracts a crowd. Warm, overcast evenings are best. Not many insects venture out under a full moon, perhaps because they are more vulnerable to predators. Although insectaphobes may enjoy the popping sounds of frying insects in bug zappers, they are attracting many more insects with the blue light than they would if they used red or amber light for illumination.

Bats, of course, are insects' flying nightmares. You can often make a good guess about a bat's identity by where you are, what time of night it is and how the bat flies. Little brown bats come out just before dusk and are often seen skimming over water near wooded areas. Big brown bats tend to fly strong, straight paths during the late evening. Silver-haired bats are slow-flying, early evening visitors to woodland streams and ponds. Hoary bats like late evenings in woody areas.

Don't forget to check for birds. Look toward the horizon, especially when the moon is low. Night migrators travel at an average of 3,000 feet, begin about 10 p.m., and peak at midnight. Such migrators include rails, nuthatches, wrens, orioles and woodcocks. Ducks, geese and loons may migrate day or night. Great horned owls are common in this area and can be recognized by their six note "hoo-hoohoo-hoo-hoo-oo" call. Some, I think, have acquired a taste for stray cats.

Which brings my narrative back to night sounds. You can hear coyotes on occasion, as they have adapted well to human population growth. The squeal of a rabbit in mortal danger also sticks in your mind, once you have experienced it. And cricket chirps can even tell you the ambient temperature if you've left your thermometer at home. (Count the number of cricket chirps in 15 seconds and add 40 to get the approximate temperature in degrees Fahrenheit.)

So, go forth into the dark and you will discover as much adventure, danger, duplicity and novelty as in any episode of "Survivor." You will find, in fact, a wealth of survivors who have made the night their own.

References

Duensing, Edward, and Millmoss, A.B. "Backyard and Beyond." Golden, Colo.: Fulcrum Publishing, 1992.

Grant, Susan. "Beauty and the Beast, the Coevolution of Plants and Animals." New York: Charles Scribners and Sons, 1984.

"Bats of Colorado, Shadows of the Night." A publication of Colorado Division of Wildlife (phone 303-297-1192).

For more information about Gary Raham's writing and illustrating go to www.biostration.com.