Forged in Flames

With summer temperatures hitting triple digits, you might expect desert parks to be lifeless landscapes. But look again.

By Jeff Rennicke

It’s hot. Even that simple recognition rises slowly across the seared plains of your brain. Thoughts tangle like heat waves. You’re surprised how difficult it is to breathe, your pulse hammering in your head, the claws of cramps tightening in your calves every time you stop—so you don’t stop. There’s no shade anyway. Then you come across footprints weaving in the sand as if from a drunk person. You’d laugh out loud, but your throat feels like sandpaper. It will be another hour before you come across the tracks again and realize they are yours.

We humans are not creatures built for heat. A rise of just a few degrees in our core body temperature can trigger severe complications, even death. Against that reality, temperatures like 112 degrees Fahrenheit in Mojave National Preserve in California, 117 degrees in Organ Pipe Cactus National Monument in Arizona, or the 134 degrees recorded in Death Valley National Park in California can make these places seem like alien landscapes, lifeless and trackless. But some species actually thrive here. The question is, how?

There are essentially three methods for living in scorching desert heat: Get tough, get out, or be very, very patient. Many desert species are nomadic, swooping in during cooler weather or after rains to take advantage of short-lived resources before getting out. Soaring birds like golden eagles and red-tailed hawks carve the summer sky, rising into the cooler air of higher altitudes. But road runners don’t have that ability. Although they can fly short distances, they prefer to use their legs, reaching speeds of up to 18 miles an hour. But even they can’t outrun the heat. Roadrunners slow down during the heat of the day, staying still for long periods to conserve energy and stay cool. They get most of the water they need by eating snakes and reptiles, and excreting salt through nasal glands to preserve water. When things eventually cool down, they’re off again, racing the desert wind.

Equally impressive despite its size (picture a handful of sand) is the kangaroo rat. It’s nocturnal, spending most of the day in a covered burrow to avoid the pounding fists of the sun. When a kangaroo rat does have to venture out, its ears and tail give off heat like radiators. Large hind feet keep it from sinking deep into the sand and expending unnecessary energy, while its hopping gait lifts it up and off the sun-baked ground. Roomy pouches in its cheeks allow it to gather and store food quickly, minimizing exposure to heat and predators.

The kangaroo rat is also an expert at minimizing its water needs. It may go an entire lifetime without a drop of free-flowing liquid. Instead, it metabolizes fluids from seeds and makes the most of every drop with kidneys that can concentrate its urine up to five times higher than humans. The tiny rodent seals the entrance to its den with cool dirt to retain moisture and even uses special membranes in its nasal passages to condense water vapor from its breath, re-circulating moisture in its system and hoarding precious fluids against the hot, dry world above.

The desert tortoise too has been sculpted by its environment. Thanks to patience, a long memory, and a fondness for the underground, desert tortoises can survive for 80 to 100 years in places where ground temperatures exceed 140 degrees. In spring and fall, they gorge themselves on succulent wildflowers and cactus. Immediately before a storm—which they can sense with a change in barometric pressure—they scratch out small catch basins in the dry soil and plot the locations on some internal map, then return when showers turn the holes into sipping pools. In the meantime, adult desert tortoises can go as long as a year between drinks, thanks to a large bladder that acts like an internal water bottle.

As the summer heat bears down, the tortoises seek shade in burrows or rock shelters to help slow water loss. When temperatures become unbearable, they use clawed front feet to dig burrows and eventually enter a state known as estivation, their metabolism slowed and systems all but shut down.

It’s a tough place, the desert, and not for the foolish or faint of heart. Survival here takes the wisdom of a roadrunner and the body of a kangaroo rat. It takes the patience of the desert tortoise, resting in a burrow beneath the surface—cool, quiet, and perfectly at home, barely aware of the distant echo of footsteps from a human wandering the dunes above, walking circles in the midday heat.

Jeff Rennicke teaches literature at Conserve School in Wisconsin's North Woods.

This article appears in the Winter 2009 issue.

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