By: Corey Buhay
It was summer in rural eastern North Carolina, practically in the middle of nowhere. Jonathan Micancin had found what he was searching for. He could hear them: frogs. Clicking and calling, trying to out-sing each other, competing for attention. It sounded like a pond full of them, not far from the river. There were two men fishing on the riverbank. They were drinking beer, talking, joking – not an unusual sight. Micancin approached these fellows, inquiring about the permission he would need to observe those frogs up close for his dissertation.
“Excuse me, sirs. Who owns that pond?”
The two fellows raised their eyebrows.
“That swamp? Ain’t nobody own that swamp but God.”
“Well,” Micancin said, “That’s good enough for me.”
Micancin, now Dr. Micancin, is an evolutionary biologist and visiting lecturer at UNC Chapel Hill. He has two earrings in his left ear, a brow that shadows his eyes, and an athletic hunch to the shoulders that likely comes from his long-time whitewater kayaking habit. In the classroom, he occasionally has a dog beside him, an ever-smiling Cane Corso mastiff named Black. In the field, it’s an armload of recording equipment and any student who’s shown an interest in catching frogs.
He works primarily with cricket frogs, a genus that exists all over the U.S., from the Great Lakes to Florida, from the Rocky Mountains to the East Coast. As cute as cricket frogs are, they weren’t his first choice.
Micancin originally wanted to study acoustic communication in birds, but when he entered graduate school at UNC, his advisor, Dr. R. Haven Wiley, saw in him another kind of potential.
“You’re really good at catching salamanders,” Micancin remembers Dr. Wiley telling him, “Study amphibians, don’t study birds.” Besides, birds wake up too early.
“I’m much better with the frogs and the salamanders. I’m a nocturnal biologist,” Micancin said. His first-choice amphibians were dart frogs. He wanted to travel to Central America, researching as his day job and moonlighting as a hiker and whitewater kayaker whenever he had time.
Unfortunately, as is often the case in scientific research, plan A doesn’t always pan out. As a new PhD student, Micancin had a hard time securing the funding to transport both himself and the necessary equipment to the tropics. Plus, even while he was applying for grants, some other scientists had started working on the very same research topic Micancin was interested in.
“A couple of hot shot, big-time professors at a couple other colleges were getting whole labs working on this system,” he said, “So I was like, ‘Okay, I’m a small fish in a really big pond, and there’s just no chance.’”
As Dr. Wiley saw it, cricket frogs presented Micancin with a perfect alternative so they turned their attention toward the evolution of Northern and Southern Cricket Frogs. Micancin wanted to study how acoustic communication could contribute to species diverging from one another.
Frogs rely on making noise to find their mates, and much like drums, the shape and size of frog can affect what kind of sound it can produce. Therefore, it’s possible that as frogs choose mates based on the sounds they made, new species evolve with the shapes and sizes corresponding to the preferred sounds.
How easy Dr. Wiley made it out to be, studying frogs right on campus at the Mason Farm Biological Reserve. Micancin was less than thrilled at first (how could Chapel Hill even hold a candle to the exotic appeal of the tropics?), and as he started to do more of the legwork, even the attraction of the plan’s potential simplicity seemed to disintegrate.
As it turns out, there were no Southern Cricket Frogs at Mason Farm. Even so, Micancin moved on, checking out other sites where both species allegedly existed. In many of these locations, the Northern Cricket Frogs were still thriving. The Southern Cricket Frogs, however, seemed to have all but disappeared.
Micancin kept looking. The search took him all over the Coastal Plain, through woods and ponds, across farms and parks, always at night and almost always in unfamiliar settings. His meeting with the riverside fishermen was one of the nicer experiences Micancin had while tramping through the rural unknown. It wasn’t like the time he heard snarling dogs running loose while working in the same county where Michael Vick had managed a dog-fighting operation. Or the time an intoxicated landowner threatened to shoot him on suspicion of robbing mailboxes.
Micancin said he had some difficulty convincing people of the Southern Cricket Frogs’ absence. They look pretty similar to Northern Cricket Frogs, so some of his colleagues figured he was either not looking hard enough or couldn’t tell the difference between the two species. Don’t be too hard on him, though; at that point in time hardly anyone could. In fact, going through preserved frog after preserved frog in museum archives around the eastern U.S., Micancin found that about 20 percent of the cricket frog specimens were mislabeled.
So he came up with a better system.
After three years of four-wheeling through dark woods, canoeing through moonlit ponds and catching, measuring and listening to frogs, Micancin was able to confirm some of the key differences between the species that had previously been speculation. One of these differences was in the sounds the frogs made. Southern Cricket Frog calls are a series of shorter, faster pulses, while Northern Frogs sing with longer, more irregular pulses.
Micancin knew the human ear could detect these differences, but what about that of a frog? To test this, he returned to his field lab, an unused garage in his family’s old farmhouse. He duct-taped together some cardboard and acoustic tile to make a large box. He then filled the box with female cricket frogs and positioned speakers at each end to play the calls of male frogs. Micancin found that the female frogs were identifying males of their own species with the same auditory cues humans use.
The other difference Micancin found between Northern Cricket Frogs and Southern Cricket Frogs was the shape of the thigh stripes on the backs of their legs. Micancin said the stripes on Northern species look like they are “drawn with a charcoal pencil – they’re thick and mottled with jagged edges.” Meanwhile a Southern Cricket Frog’s thigh stripes “look like they were drawn with a watercolor pen. They’re very well-defined and thin and elegant-looking.”
Micancin also found the size of a frog’s anal tubercles, or “butt warts,” was also a good indication of its species, but he left most of those measurements to overeager undergrads.
Now that he knew what was what, Micancin could go back through the records and find out if the Southern Cricket Frog really was disappearing.
Fortunately, he had a distant predecessor, the “mad genius” Peter N. Barlett. Bartlett had collected, almost obsessively, 800 cricket frogs from 130 sites in the early 1960s. Micancin and his colleagues were able to compare those samples to recent cricket frog specimens and found that there was a very good reason Micancin had had such trouble finding places where Northern and Southern Cricket Frogs coexisted: Southern Cricket Frogs had completely vanished from about 14,000 square kilometers of their former habitat sometime in the last 60 years. The Roanoake, Tar and Neuse River basins are among those that the Southern Cricket Frog no longer calls home.
In Micancin’s words, cricket frogs are the popcorn shrimp of the amphibian world. Everything eats them. They’re an important source of food for many predators, and they have historically been a very common genus, so much so that one of Micancin’s colleagues couldn’t believe he was studying such a mundane creature (Northern Cricket Frogs are often called “parking lot frogs”). Cricket frogs have always been ubiquitous, and that’s why their disappearance is so concerning.
So where did the Southern Cricket Frog go?
Micancin has some ideas. He and his colleagues took tissue samples from hundreds of male frogs they’ve collected and studied in the field. Some of their analyses of these samples point to a possible hybridization between the two species: some of the Northern Cricket Frogs appear to have Southern Cricket Frog DNA.
But why does the replacement of one species with another matter? What do the predators care if the frogs now sound a little different and have bigger butt warts?
While Southern Cricket Frogs may be ceding their lands to a similar species, other amphibians aren’t so lucky. In fact, Micancin speculates that many other unique, local species – like Tiger Salamanders, Oak Toads and Pine Barrens Tree Frogs – face a plight similar to that of the Southern Cricket Frog. The Southern Cricket Frog merely stands as representation for all species that suffer from human interference and habitat loss. Unfortunately, these other, more rare species are less common and therefore both difficult to study and more vulnerable to population decline.
It’s not news that amphibians are disappearing. Civilization leaves little room for natural variation in the ecosystem. It smoothes out that variation with roads and parking lots, fields and farms. We make everything around us look the same; with us spread the species that are used to our surroundings. House flies, house mice, cockroaches, rats, weeds, certain types of bacteria…all these swarm in our wake, and these species take over once we’ve destroyed the more delicate native habitats.
For the Southern Cricket Frog, this means the destruction of the fleeting seasonal ponds, called ephemeral wetlands, in which they have evolved to survive.
Farmers drain some ponds and fortify others. Permanent ponds are a good source of water, and drained land is good for planting, but to a farmer, an ephemeral wetland is useless. Northern Cricket Frogs, the parking lot frogs, are generalists when it comes to habitat. They are happy to take over retention ponds and agricultural ponds. Meanwhile, the Southern Cricket Frog, a habitat specialist, has few homes left.
The ecology of the Coastal Plain is part of what defines North Carolina, and the rapid disappearance its unique habitats, like longleaf pines and ephemeral wetlands, is changing the face of the state. Even N.C. State University is selling off their large reserve of longleaf pine woodland for a little extra capital. What has long been the iconic habitat of both native amphibians and Tar Heels is vanishing.
“This type of habitat is going to be turned potentially into golf courses. And condos,” was Micancin’s speculation.
All the more habitat for the “parking lot frogs.” But is that really what we want?