Recently, I had a chance to spend a couple of days exploring Arizona’s Sonoran Desert. It’s truly amazing to see how all the different animals use the desert to make a living.

The Sonoran Desert is spread across 106,000 square miles with about 40 percent of it in the U.S. and 60 percent in Mexico. It ranges in elevation from near sea level to over 3,300 feet along the eastern edge of Arizona. In Arizona it receives both winter and summer precipitation with an annual average of about 13 inches.

It is the most biologically diverse of the four big North American deserts. In fact, there are more than 1,000 species of solitary and social bees in the Sonoran Desert — more than anywhere else on the globe.

Being trained as a tree root physiologist, I’m always curious about what’s making a living on the ground. Digger bee holes are very evident with a quarter of an inch hooked-top chimneys dotting the earth. The hooked chimneys are believed to thwart the attempts of parasitic hoverflies, who are known to flip eggs into bee holes — their eggs attach themselves to the bee eggs, once hatched they devour bee eggs.

Digger bees are solitary and the female will lay one egg with a packet of honey and pollen in up to 18 cells in one below ground nest consisting of 7 feet of tunnels.

Nearby the digger bee holes, I noticed a circular hole about an inch-and-a-half wide covered with silk; just outside the hole were some loose barbed, dark hairs — indicating a tarantula burrow.

Tarantulas are one of the most recognized residents of the southwest desert. These nocturnal hunters often wait at their entrance holes for beetles and grasshoppers that pass by. Upon entering their hole after a night of hunting they weave silk at the den entrance. The silk has at least two purposes: It keeps the burrow dry by holding humidity and it carries vibrations down to the spider allowing it to know what’s occurring above the ground.

Tarantulas defend themselves from foxes, coyotes, raccoons and skunks by rubbing their legs against the abdomen to loosen their barbed hairs, which are designed to severely irritate the eyes or nasal cavities of predators.

White-nosed coatis, a much larger relative of the mink and closely related to raccoons, are known to grab tarantulas, roll them vigorously on the ground, dislodge their barbed hairs and then feast upon them.

In a sparse clump of grass about a mile away from the tarantula den I spotted a hole in the ground about an inch-and-a-quarter wide, sitting nearby I waited for its occupant to surface. Soon a fierce little predator, a grasshopper mouse, appeared. These diminutive yet tough critters hunt lizards, grasshoppers, beetles, scorpions and even other mice.

Grasshopper mice cooperate by raising their young and teaching them to hunt. Young mice learn how to bite the stingers off scorpions before eating them, and how to disable stink beetles — inch-long bugs that defend themselves by performing a headstand and spraying a fetid smell from their posterior.

One of the more eerie desert sounds at night is the high-pitched howl of grasshopper mice. If cornered by a predator this miniature beast will drop a runny, very smelly bowl movement in a last ditch attempt to escape — an uncommon trait for a mouse. 

One of the most fascinating and easily my favorite animals of the Sonoran Desert are the Couch’s Spadefoot toads. They are the largest native toads in the U.S. measuring a whopping 7 inches in length. 

These incredible animals sleep for almost one year in the earth. The vibrations of the first summer thunderstorm awaken them and they burrow their way to the surface where they congregate in temporary rain pools and puddles in desert washes, irrigation canals or ponds.

Because water is so scare in the desert, they breed immediately and females lay eggs within 24 hours. Tadpoles must race to become toadlets before the ephemeral pools dry up — from egg to toadlet in less than 14 days.

Adult Spadefoot’s are insectivores with termites being their preferred prey. An adult requires just two meals on termites, then with their hard keratinous spade-like pad on their hind legs they bury themselves in the ground. This exceptional desert dweller can live for over 10 years.

Burrowing owls are the only owl or raptor (bird of prey) to den and nest in underground digs. Excellent eyesight helps them spot predators. They prey on rodents, beetles, moths, scorpions, grasshoppers, prairie dog pups, toads, young snakes and other reptiles.

Snakes, badgers and coyotes preyed upon burrowing owls. Mature burrowing owls have developed an intriguing defense mechanism — they imitate the sound of a rattlesnake, which often frightens predators away.

Arizona’s Gila monster is one of the most unusual reptiles in the world and one of only two venomous lizards (the other is the Mexican beaded lizard) known on the globe.

Gila monsters spend 90 percent of their lives in natural crevices under boulders or rocks.

This beauty of a beast can eat 35 percent of its body weight in one meal and store excess as fat in its tail. You can’t miss its bright black and pink coloring, and beaded skin.

These shy animals release their venom by biting down on the victim with needle-sharp teeth hidden by the gums when not in use.

Gila monster venom may very well become the next blockbuster drug; currently it’s being studied for treatment of high blood pressure that afflicts over 73 million Americans.


Dr. Reese Halter is a public speaker and conservation biologist. His most recent book is “The Incomparable Honeybee and the Economics of Pollination,” Rocky Mountain Books. Contact him through

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