It's cooling off a bit after the heatwave of the last weeks, but in the desert "cooling off" can be a relative term. It's still hot. Desert dwellers with any choice hunker inside during the heat of the day, waiting for that big glowing ball in the sky to go away. And for most of those desert dwellers, "inside" means inside a hole in the ground.
There are exceptions, of course. A few animals don't seem to be fazed much by the heat. Cactus wrens and ravens and the desert's various jays find a little bit of shade when they have to. Coyotes use excavated dens to raise their pups, but stay aboveground after they're grown. Some animals hang out in holes that aren't in the ground: ladderbacked woodpeckers, for instance, dig holes in trunks of Joshua trees or the occasional saguaro.
But in summer, at least, a lot of the desert's wildlife, perhaps even a majority of it, goes below the surface. The group America famously sang that the ocean is a desert with its life underground, and now you've probably got that song stuck in your head for the rest of the day, and I apologize. But the desert, for the most part, is also a desert with its life underground. There are entire ecosystems of holes in the top six feet or so of stony soil, entire communities of holes, holes that are excavated by one animal and adapted by another and then another, in the underground housing equivalent of a food chain.
It makes sense. Air temperatures in the inch just above a patch of exposed desert soil can easily top 150° on a hot day. Dig a foot or two down and angle your hole so the sun doesn't shine into it and you can find yourself cool and comfortable at somewhere between 60° and 80°. A partially-enclosed hole with little air circulation helps conserve exhaled moisture, its relatively humid air keeping an animal from dehydrating as it breathes. Holes provide shelter in an environment that doesn't offer much shelter, not just from the elements but also from those above-ground coyotes and ravens.
And throughout the desert, places where it's relatively easy to dig a hole abound. There are few roots to bind the soil in an impenetrable mat of sod and tree root. Where roots do grow they tend to belong to shrubs that accumulate loose soil around their bases, perfect for kangaroo rats and ground squirrels and other small animals who can build homes reinforced by the shrub's roots.
If you need a larger hole, there are plenty of cutbanks and slopes carved into the desert by flash floods, readily excavated with a few hours of effort. In places that the local humans have left alone for a few decades, there are also pre-owned holes that can be acquired and spruced up. On occasion, an animal such as a rattlesnake or a badger will acquire a hole as a side benefit of eating the previous tenants. Fairly often an animal will move into an already-occupied hole with happier results for all: scorpions often move into occupied ground squirrel holes and both residents seem to coexist just fine.
There are enough ready-made holes in the desert, in fact, that some species who are utterly committed to the subterranean lifestyle can thrive even if they're unable to dig their own houses. Take burrowing owls, for instance, which don't last long without holes of just the right size, but have no way to dig their own. They can, however, move into holes dug by rodents, rabbits, tortoises or larger animals and make slight modifications on the inside.
A key consequence of the desert harboring so many hole-dwellers is that desert visitors of the two-legged, water-bottle-toting variety may visit a highly populated, consummately biodiverse stretch of desert and get the impression that there's no wildlife there at all. A clever visitor discovers his or her mistake when hiking onto a patch of inviting bare soil only to sink a foot or two into the earth with every third or fourth step. Much apparently undisturbed, barren desert soil is in fact honeycombed with tunnels, and veteran desert hikers learn to stick to sandy washes when they can in order to avoid collapsing someone's home. This isn't entirely altruism: there could be rattlesnakes down there. It's unlikely but not impossible.
The Arizona-Sonora Desert Museum Press publishes a quirky, entertaining and informative field guide to holes in the desert, which is sensibly entitled "A Field Guide To Desert Holes." Author Pinal Merlin describes ground holes ranging in size from anthills and spider nests to rodent and tortoise burrows and coyote dens, as well as holes in trees, rock crevices, depressions animals scoop out to rest in, and a few other related concavities. Though it's focused on the Arizona portion of the Sonoran Desert, it's quite useful in the California deserts as well.
It's just another example of the desert hiding its treasures from us; a seemingly desolate expanse of sand and rock can be as intricate and biologically diverse as a coral reef. But unlike a coral reef, you don't need specialized equipment -- or even a plane ticket -- to get to know them. A little study, a little patient observation, a few moments of having your boots plunge into the soil unexpectedly, and you develop the sense that you're walking around on the fragile meniscus of an ocean of sand with entire schools of things living just below.
And, after a while, in the desert you can remember their names.
Chris Clarke is an environmental writer of two decades standing. Director of Desert Biodiversity, he writes from Joshua Tree regularly at his acclaimed blog Coyote Crossing and comments on desert issues on KCET weekly. Read his recent posts here.
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