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To go in the dark with a light is to know the light.

To know the dark, go dark. Go without sight,

and find that the dark, too, blooms and sings,

and is traveled by dark feet and dark wings.

–Wendell Berry, “To Know the Dark”

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There is a certain phase between day and night, a time of transition, where the diurnal blends into the nocturnal. These periods of emergent light and shifting darkness make up the twilights of the day—the bimodal intervals between dawn and sunrise, and between sunset and dusk. This is a time on the edges, on the border of binary classification. Organisms that make their way about in these in-between times are known as crepuscular. Those active strictly in the morning twilight are the matutinal; those active solely in the evening twilight are vespertine.

Many familiar creatures make their way about in this altered level of light, taking advantage of both the dimness and the illumination. This is the time to be crepuscular. Under these conditions, a multitude of large forest dwelling creatures emerge—bear, deer, moose—along with their small mammal compatriots: skunks, raccoons, possums, rabbits. Many creatures of the air take flight. The insects—mosquitoes, moths, fireflies. The birds—the owls, the nighthawks. The charismatic bats also take wing. It is now that the active behaviors of these creatures peak. To bear witness to these crepuscular awakenings, the intrepid observer must come join the experience, without light, as a member of the dark.

You are in the middle of it now. Let your feet and voice be silent as you travel in deeper. You will find that the woods are alive with sounds and movements. Careful! Listen close! You too will hear and know the character of the fading light. Though the growing darkness distorts your human vision, fear not. There is nothing to be afraid of in these woods. Nothing in the night is any more dangerous to you than during the day. With transformed senses and unfamiliar sensations, your mind fills in the gaps and imagination runs wild. Yet don’t be alarmed. These crepuscular creatures are more afraid of you than you are of them. Relax. Stay a spell. You may become privy to the hoot of an owl or catch the gliding wisp of a bat overhead.

This twilight journey has been a distinctive experience for you, for humans are not crepuscular creatures. We are largely diurnal, adapted to the brightness of day. Our main sensory experience, our vision, works best in broad daylight. As the day fades into twilight, our eyes begin to cope. The iris expands and the pupils dilate to allow in the dissipating light. Inside the eye, the cones—the sensory cells that detect color and detail—begin to shut down in the dimness. Colors begin to fade, details blur. The acuity of vision diminishes. Yet within the eye, the counterpart of the cones—the rods—begin to become engaged. With the activation of the rods, contrast and shadow become keener, movement more detectable. The silhouettes of trees overhead begin to pop against the dimming sky. The rods readily pick up movement in the periphery of your vision. What was that?!? Did something move? In your periphery, you may detect movement, but oh what tricks your mind may also play on you! The darkness is unfamiliar territory; you are more wary, more attuned to sudden movement.

Yet there are creatures about. There is an abundance of life that is indeed adapted to the crepuscular world. The fading light offers a veil of protection for easy prey, yet illumination enough by which to forage. Predators, too, make use of the twilight as a time of feeding. Equally adapted to the hunt, the crepuscular predators seek out their crepuscular prey. In the twilight, the never-ending battle of evolution ebbs on. Owls, marauders of the night sky, have large eyes adapted to gathering the few rays of light available; binaural hearing, also known as asymmetrical ear placement, allows the owl to detect differences in sound occurrence down to 30 millionths of a second, letting them pinpoint even the tiniest rustle on the forest floor. Overhead the sky is filled with the noise of sound waves, inaudible to the human ear. The bats have emerged and fill the night sky with their echolocation. By emitting their sonar in flight, bats are able to precisely locate the abundance of crepuscular insects upon which they feast. It is a world of eat and be eaten.

All daylight has now faded. At astronomical dusk, the light from the sun no longer can reach over the horizon—it is now as dark as it can get. The period of crepuscular animals is ending. Patiently they will wait again until the next time of twilight. Truly nocturnal animals now make their way about the forest. Take a moment to gaze up now. The sky abounds with a brilliance of stars. Even in the dark, light from a thousand distant suns still caress the planet with their brightness. Even in the darkness, there is light. Even in the darkness there is knowing.