Mr. Bonesall — students nicknamed him “Bonesaw” — was a hulking Marine Corps combat veteran with a crew cut and tattooed arms. His icy blue eyes glinted with a don’t-mess-with-me attitude, but his countenance softened during lectures on advanced biology made to high school students in accelerated college prep classes. He was one of the best teachers I ever had.

It was Bonesaw who convinced my parents to allow me to take several college courses in the 11th grade. One of these -- The Class Amphibia -- he taught on weekends at the local university.

It was in his class that I learned about and never forgot a world of creatures that most people don’t see or appreciate. But rural residents of Appalachia hear their songs of orgy from late winter through summer.

Bonesaw taught me about frogs and toads.

Bonesaw not only required us to memorize the scientific names of these animals, he led students into the field to study amphibians in their natural surroundings.

His favorite forays were to swamps and vernal pools, where breeding occurred to a cacophony of croaks, peeps, trills, whistles, chirps and bass rumbles. It all began on frigid March nights.

In rubber boots and with carbide light helmets strapped to their heads, Bonesaw’s amphibian hunters waded through the flooded meadows and temporary pools where new generations of frogs and toads were created. We collected not only live specimens of adults for study, but large masses of gelatinous egg clumps and strings. These were brought back to the classroom to be hatched in aquarium tanks.

Often, the temperature would be near freezing with snow spitting from the dark sky when Bonesaw’s troops waded into the swamps. Getting soaked was an occupational hazard in his batrachology class. Being cold was the norm. But boredom never was part of this learning experience.

On warm nights in early spring, water snakes were out, preying on the amphibian buffet. It was unnerving to look down and see a moccasin slithering between your legs. There also were encounters with coons, minks and even skunks.

I remember standing knee deep in a vernal pool where rimes of ice had formed on the moss, but I saw my light reflected from the eyes of hundreds of frogs gathered to mate and lay eggs. This ritual of copulation and fertilization had been going on since before the age of dinosaurs, according to Bonesaw. It was humbling to a teenager worried about how to ask girls out on dates.

Mainly, our wetland safaris focused on a particular species of breeding frog or toad. We studied its peculiar habitat and life cycle, what it ate and what ate it. And Bonesaw taught us to recognize the amphibians by their springtime voices.

Eventually, I chose a different career path in college, but Bonesaw’s batrachian adventures still stand out as a unique part of my education. So much was I influenced that, to this day, I continue to have more than a passing interest in Appalachian amphibians.

Guests are therefore surprised on spring evenings when we grill on my deck, which overlooks a small pond and wetland meadow caused by rain overflow. As some people identify birds by their voice, so I can pick out frog and toad species by their songs.

Surprisingly the amphibian symphony started early this year. Despite the severe winter, spring peepers were heard in the last week of February. These small frogs have the scientific name Pseudcris crucifer and are recognized by the X in their backs.

Later the leopard frogs joined the musical movement. Wood frogs, tree frogs and chorus frogs chimed in, and later the varied members of the toad family added their notes. Finally the timpani of bull frogs reverberated across the teeming shallow waters.

On still nights, the rills, peeps, purrs and hiccups combine with the bull frogs’ bass line to form a springtime paean, a melody of procreation and ancient ardor that most humans don’t slow down and allow themselves to hear. My old biology teacher, Mr. Bonesall, opened the ears of his students, and I have never forgotten.

■ Steve Oden is an award-winning columnist and former newspaper editor in Tennessee and Alabama.