Flashlight-Free Night Hiking - Time To Try It
Durango Herald, Jan 9, 2006
Leigh Gillette, Program Director

The natural world assumes a whole new character at night, and darkness provides an opportunity to sharpen senses other than sight.

Winter’s scant daylight hours make it hard for many of us to fit in an outdoor experience. I get my nature fix by hiking after sunset. The natural world assumes a whole new character at night, and darkness provides an opportunity to sharpen senses other than sight.

On a recent night hike on a deserted dirt road near Junction Creek, my fiancé Kevin and I heard owls and coyotes calling, and felt changes in air temperature as we passed sun-warmed south facing rocks and cool north facing ledges. Although we didn’t use flashlights, we weren’t stumbling sightless in the dark. Moonlight and starlight were all we needed to navigate.

Without some sort of light, no one sees, but a life under electric bulbs has skewed our perceptions of how much light we need for basic sight. Healthy human eyes have an impressive capacity to adapt to dim light conditions. A little understanding of eye anatomy and physiology can shed some light on the mysterious topic of night vision, and hopefully lure you out for a safe nocturnal stroll.

Eyes are light detectors, designed to admit light, focus it, and detect the patterns and colors translated by the brain as visual sights. Light enters the eye through the pupil – that dark spot at the center of the colorful iris of the eye. The lens behind the pupil focuses that light onto the retina, a special layer of light-sensitive cells lining the back of the eyeball.

The retina contains two basic types of light-sensitive cells: “cone cells” for color vision, and “rod cells” for black and white vision. Cone cells can only be triggered by high amounts of light; therefore, we typically see color only during daylight or other bright light. Starting an evening hike under a brilliant sunset is a great way to enjoy your last natural view of color for the day. As the light fades, so does your color vision as your cone cells deactivate.

Rod cells are for night sight! While they cannot provide strong detail, rod cells are incredibly sensitive to small amounts of light, and continue to send signals to our brain even in the dimmest of light conditions.

Each rod cell contains rhodopsin (ro?·dop·sin), a light-sensitive chemical. Rhodopsin degrades in bright light, and builds up in darkness. The more active rhodopsin you have in your eyes, the better your night vision. Stepping from a well lit- building or car onto a nighttime trail, expect to be night-blind, since the bright lights have degraded all your rhodopsin. But as the rhodopsin regenerates in your eyes, your night vision will increase quickly and dramatically. Within 5 minutes, active rhodopsin can increase 100 times, while your pupils simultaneously dilate to 10 times their previous diameter. With five minute’s patience, you can expect your night vision to improve 1000 fold.

Here’s to “seeing you” on the trail tonight! Night hikers, unite!