On March 19 I drove out to the Superstition Mountains, under a threatening sky split with trembling shafts of sunlight. It had rained the night before and again that morning, and as my hiking pal and I set out on the Second Water Trail the cool air was heavy with humidity and sweet with the scent of desert plants.
At the outset the trail descended gently to a boulder strewn wash. It was obvious that in rain events water thunders here, draining mountainous faces that loom craggy and forbidding. Familiar desert trees were joined by lush vines, and lichen and moss sprawled across rocky stretches. Timid lupine, larkspur and hyacinth shyly presented their spectrum of blue blossoms while brittle bushes and creosote flowered in bold yellow.
We hiked for several hours and the day was warming when I noticed movement at ground level. Expecting a lizard, I was astounded to see a small brown frog hop across the trail. He reached the shade of a large rock and slipped out of sight. It was a canyon treefrog, known for cryptic coloring that helps it hide in a variety of habitats.
The canyon treefrog is usually found in rocky canyons in riparian areas. This might be in the desert, in desert grasslands or oak-pine forests. The frog survives in elevations up to 9800 feet, avoiding cold temperatures by retreating to underground burrows.
I saw another frog a week later. I was outside with my Mesa Community College aquaponics class when one of the students spied a frog. It’s an evening class and we often walk over to the greenhouse, adjacent garden, and aquaponics systems to work. As we approached the dimly lit garden, a large frog hopped across the path.
Our professor scooped him up and held him so we could all admire his olive green coloring and dark green blotches. “This is a Couch’s spadefoot,” Dr. Brooks announced. “When I was a kid these frogs used to be everywhere.” The frog’s large eyes bugged out at us from the top of its head.
Apparently back in the day, spadefoots were a common sight in the evening times, especially in areas with sandy soils where drought hardy creosote and mesquite trees grew. Back then people knew the eerie nighttime scream they heard on monsoon nights was the mating call of this frog.
Mating season coincides with the torrential rainfalls of late summer. The spadefoots are called from their underground homes by the drumming of the rain on the earth and by the rumble of thunder. The males come up out of their burrows and immediately start calling the females. In The Natural History of the Sonoran Desert, the call of Couch’s spadefoot is described as the bleating cry that a sheep or goat might make. I would guess most of us aren’t familiar with that sound either.
Females lay thousands of eggs which can hatch in as little as 15 hours. The tiny tadpoles transform quickly into frogs, driven by the rapid shrinkage of the pools where they spawned. The brand new frogs hide under vegetation or anyplace slightly moist, and eat and eat. They feed on grasshoppers, ants, beetles and spiders. This may be the frogs’ only chance to eat until the monsoon season rolls around again. The horny growths or “spades” on their back legs help the frogs dig down into their protective burrows.
Frogs in the desert strike me as improbable, and in these days, nearly impossible. But nature has found a way to put amphibians into our arid landscape and allow them to flourish. As much as Nature favors delicate yet resilient amphibians, humans have mostly stayed immune to their charms and ignorant of their ways.