Spadefoot Toads: Desert Amphibians
What was that weird noise coming from behind my house?
The concert of hoarse calls woke me about 3 A.M. one August
night after two days of torrential rains.
Could it be the mysterious spadefoot toads I had read about? At the time, I was living by the desert grasslands near Santa Fe, New Mexico. I had hoped to see some spadefoots.
The desert spadefoot is a small olive-brown creature about two and a half inches long. It is an amphibian, related to other toads and frogs. Like its cousins, it eats insects. Most toads and frogs are found in wet or moist places, but spadefoots live in a desertlike environment. So they have to have special ways to survive in a dry world.
Secret
Burrows
The spadefoot toad is named for the sharp, hard, black bump
on the underside of each hind foot.
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Each
of the toad’s rear feet has a hard, black bump
for digging.
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It uses this “spade” to bury itself by digging backward into the sandy soil. The toad can stay in its secret burrow for days, months, or even a year without eating, waiting for a heavy summer rain.
The morning after the late-night concert, I walked out to the big sandy ditch behind my house. Usually the ditch was dry, but it had a trickle of water in it this morning. Following the ditch, I soon came to a monster muddy rain pool.
Suddenly I saw five or six small brown toads swimming around in the puddle. They were floating on their bellies, legs stretched out behind them, their heads out of the water.
Every few seconds they called, inflating huge, balloonlike vocal sacs on their throats. They looked like a bunch of kids blowing pink bubble gum.
Calling
for Mates
The
hoarse calls were mating calls. As the males called, other
toads, which were females, swam around them. Over and over
the males tried to grasp the females. The females swam away,
only to go back as the males called again.
This courtship game lasted several minutes. Finally, each male spadefoot succeeded in clasping a female from the back.
The clasping stimulates egg-laying. Then, when the female lays her eggs, the male is there to deposit his sperm on them.
Suddenly the pool was quiet. The calling males had all found mates.
That evening I caught one of the toads. At home, I put it into a fishbowl with about two inches of moist sand in the bottom. The toad quickly dug itself backward into the sand with its hind feet, making a wiggling, side-to-side motion.
After about sixty seconds, all I could see of it were its eyes. Then the toad closed them into little slits, and soon they, too, disappeared under the sand.
Young
Toads
Wading
into the rain pool the next morning, I found many small
jellylike blobs attached to the grasses in the water. In
the jelly were many clear eggs with dark spots inside.
On the next day I saw some newly hatched quarter-inch tadpoles clinging to the tattered remains of the jelly. The shallow pool was beginning to shrink in the hot sun. In the mud around the edges was a network of tiny toad tracks, the only trace of the adult spadefoots.
Each
day the pool got smaller. By the end of the week, it had
shrunk to a strip of water just a few inches wide, crowded
with hundreds of fat-bellied, long-tailed tadpoles.
To survive, the tadpoles would have to change quickly into fully formed toadlets. They would have to be able to live on land before their watery birthplace dried up.
As the pool shrunk, many tadpoles’ hind legs grew large enough to be seen easily. A few began to sprout front legs.
And then on the twelfth day, I found dozens of miniature spadefoot toads hopping around the edges of the puddle. Some still had long tails. Some had stubby tails. Others had none. All of them had four legs, little toady bumps on their skin, and two beady eyes on the tops of their heads.
Countless tadpoles had died. But some had won their race against the disappearing rain puddle.
I watched one dig itself into the sand nearby. There it would hide safely until heavy rains signaled it to meet other toads in a rain puddle. Then the life cycle would start over again.
