Yesterday, in the darkness at exactly 6:00 am, I heard a high-pitched screech outside my window, which turned into a squeal. Finally the call evolved into one I recognized: a Barred Owl, the familiar denizen of my park. After a short but fierce inner argument between the Voice That Wanted To Stay In My Warm Bed, and Naturalist Voice, the naturalist won and I dug myself out from under cats and covers, pulled on pants and a jacket, and ventured out into the dark street to try to spot the light-gray owl in the thick trees.
Unfortunately, the conifers along my street were too dense and tall for me to find the owl, who stayed quiet after that. So after my brief foray into the dark morning, I (quite happily) went back inside and crawled back under the covers to read for a while with tea and juice, knowing contentedly that the owl was somewhere nearby.
We humans, as you may have noticed, are pretty much diurnal: we’re active during the day, and if we’re out and about at night, we go where there are artificial lights. You can tell this is what we’re made for by looking at our faces.
Portrait of Nick
Can you see the sign of diurnality yet? By contrast, here’s another image, of a creature who’s nocturnal, active at night:
If we put these two handsome faces side by side, we see the clue: how much larger a proportion of the face the eyes take up in the nocturnal mammal.
Eye proportions in facial dimensions
Making a living in the world of night requires large eyes (or, if you’d rather live by another sense, huge ears). These eyes may allow you to find your prey—
Barred Owl (left), possibly the one who called at 6 am; Northern Saw-whet Owl (right)
—or to spot night predators, hoping to avoid becoming prey.
House Mouse. Note her big ears, also helpful for nocturnal living.
Lincoln Park, West Seattle
Why would a creature choose a nocturnal world rather than hunting in daylight like we humans do? One reason is that we, and other animal daylighters, just aren’t around as much in the dark, meaning you’ve got the world more to yourself, avoiding some competition for scarce resources.
Another reason became apparent a year ago at this time, when I spent a glorious two weeks rafting down the Grand Canyon. Barely two hours after we launched on our first day, we came across these.
Footprints, Grand Canyon.
Rear (on left) and left front foot (on right).
We never saw this creature. Still, we can learn a lot about her from the traces she left behind.
The creature who pressed her feet gently into the red sand had small oval corn-kernel toes, but her claws were recessed enough that they didn’t make impressions. Canine claws don’t retract, so this must have been another species.
Why the difference in pawprints? If you’re a canine—which in the Grand Canyon means a coyote or gray fox—your thing is running. Your legs and feet are built for chasing prey over long distances, and your claws help you grip the ground as you run, and to dig after prey that may be lucky enough to find a burrow while you’re after it. So having those claws ready to go for the long haul really helps you out.
But if you feed yourself by leaping and climbing after prey, you need different paws. For example, imagine you’re a cat. Cat hips, shoulders, loose skin, and musculature are designed to propel you up after arboreal prey that scampers along branches, or aerial prey that’s a bit too oblivious of your sneaking presence as it feeds near the ground. Keeping your claws sheathed keeps them nice and sharp for the sudden attack; if you regularly let them drag on the ground, they’d be too dull to work well for your purposes.
So our pawprints belong to a kind of creature that isn’t a canine. The only Grand Canyon mammal that has five toes fore and aft, and whose claws don’t always reach the ground, is the ringtail cat (Bassariscus astutus), a member of the raccoon family. She’s a marvelous creature, agile and with those endearingly huge eyes.
Ringtail cat (Bassariscus astutus) by moonlight, Grand Canyon.
Photo and painting by Trileigh Tucker.
The ringtail has done a good job making a living in a hard place. Her species is so well adapted, in fact, that it hasn’t needed to change its basic characteristics for over two million years, since it first appeared in the late Neogene. What does it take for a small mammal to make a good home in a desert? Well, when you think of the Arizona desert, what words come to mind? Dry. Hot. So our little ringtail, like other desert-adapted animals and plants, has had to find ways to deal with heat and desiccation. I’ll leave desiccation for another time, but let’s think for a bit about what it takes to deal with heat.
Look again at her face.
Ringtail cat at night. Painting by Trileigh Tucker.
If you have large eyes for the size of your skull, your eyes have bigger pupils and lenses that let more light into your eyeball, where your large retina can collect more of that precious light to provide useful information to your brain. Of course, the space taken up by those big eyes in your head mean there’s less room for other things like eye muscles—so in order to look around for your dinner, or for someone such as an owl, coyote, or bobcat who might make dinner out of you, your neck has adapted to let you twist your head widely around.
Your eyes also have many more rods (which are sensitive to low light levels) than those of daytime hunters, but far fewer cones to help you see color and focus precisely. That means your color vision’s pretty bad and you need a large-screen TV—your big retinas—to give you enough information to interpret an image.
In summer, when our ringtail left those tracks, it’s hot as heck out there in the daytime. So, many creatures of the desert protect themselves from the heat by hiding in shelters during the day, venturing out only at night when the temperature may drop to a relatively chilly 95° rather than 110°. All these visual adaptations ultimately mean that you can capture prey at night, when it’s cooler, and that’s a big plus in this Hot Dry Place.
* * * * *
We diurnal creatures usually know the night-dwellers only by their traces: a ringing call before dawn, small footprints in soft sand. We share the same place but on different cycles, different wavelengths, like AM and FM radio channels in the same atmosphere.
What else are we unattuned to? What other presences permeate our perimeters, recognized only by accident or fortune?
I once bemoaned to a dear friend my sense of having been misled, when I was a child, by adults who told me the world was full of pixies, Santa Claus, brownies who hide behind curtains: pervasive magic. His wise reply was that perhaps every spiderweb, salamander, soaring hawk, sparrow’s song, were the living manifestations of such mysterious spirits. Presences clear in the light of day and those hidden by night, keeping us alive to mystery, if we can listen for the echo of a call, find the shadows of tiny toes in the sand, catch the trace of a tail, feel the soft breath of Presence whispered in our ear.
Lizard tracks at busy intersection, Grand Canyon.
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