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A search for the rare and elusive Eastern Spadefoot Toad

May 7, 2014

The Eastern Spadefoot Toad, so named because of a digging device on each hind foot, is a beautiful creature with bright yellow cat eyes. It spends most of its life underground, often for years. Following deluges in May and beyond, the amphibian sometimes resurfaces to call, court, and reproduce. A small population of these animals did just that recently—a fine birthday present for the Naturalist.

This may surprise you, but one of my all-time favorite series of books is not the journals of Thoreau, the peregrinations of Edwin Way Teale, the chronicles of Bernd Heinrich, or any of the fine collections of work by other luminary naturalists. No, in my pantheon of great and enduring reads is the Harry Potter series by J.K. Rowling. And among my most memorable of Rowling creations is a giant of a teacher and friend known as Rubeus Hagrid, the gamekeeper of Hogwarts Castle and the instructor of a class about the Care of Magical Creatures.

I thought about invoking Hagrid last week when I had an encounter with one of the most magical creatures in my world. This would be the Eastern Spadefoot Toad, an amphibian whose survival abilities and lifestyle verge on mythical. Spadefoots, handsome amphibians that can, as an adult, fit easily in your palm, are exceedingly scarce in our area. According to URI wildlife ecologist Peter Paton’s authoritative Rhode Island Vernal Pools website (www.uri.edu/cels/nrs/paton/), Scaphiopus holbrookii, as the creature is known to science, is “probably the rarest and least known species of frog that occurs in Rhode Island.” It’s considered threatened in Massachusetts, where its last remaining stronghold is Cape Cod. And in Connecticut, the spadefoot, named in recognition of the digging tools on its hind feet, is a state-endangered species.

Hagrid never dealt with these amphibians, but he would have been impressed, for spadefoots can, in a very real sense, cheat death and, in the process, live for a very long time—well, for a small amphibian. Here’s how they do it.

Imagine you’re an adult toad and you’ve just bred successfully in a vernal pool. In the spadefoot’s case, however, “vernal” is something of a misnomer, in that these amphibians are typically summer breeders and seem to choose depressions that don’t fill in the spring, like traditional vernal pools, but rather wait until the arrival of monsoonal thunderstorms in June through August. On the rare occasions when this happens—one trigger seems to be at least several inches of rain within a day—the spadefoots appear out of nowhere, immerse themselves in the water, court like crazy, and mate, after which the females lay upwards of 2,500 eggs. With their important work done, the adults melt back into the landscape. Perhaps they feed and fatten up for a while; perhaps, if the weather conditions are right, they might even return to the ponds for another round of courtship activities.

In the temporary ponds, the eggs hatch quickly—often within a few days—and the tadpoles grow fast on a diet of algae, tiny invertebrates, and, occasionally, their brother and sister tadpoles. In about a month, the larvae metamorphose and leave the pond as thumbnail-sized toadlets. These probably feed for a period of time and then, they too disappear.

But where? Here’s what I consider the magical part: spadefoots use their hind-feet shovels to tunnel into the sandy soil—deep into the sandy soil. There are reliable stories of these toads digging down more than six feet below the surface, and once there, they secrete a mucus that forms a moisture-trapping cocoon. Then, they enter a kind of suspended animation and, barely alive, they await resurrection, natural-history-style. Rising from something close to death may happen within a year or, in rare but probably true cases, it may take as long as 20 years for the right conditions to occur: rains during relatively warm weather that are heavy enough to percolate down to the spadefoot’s hiding places. It’s also possible, but by no means certain, that the amphibians might also respond to the soil-penetrating rumbles of thunder as wake-up calls.

Whatever works took place at the end of April this year, when we had about 3.5 inches of rain in the ridge gauge, and that, atop more than 6 inches of precipitation earlier, apparently did the trick. On May 1, the night of my birthday, I had this strange feeling that I should visit a pond I’d been checking for years. At the beginning of July 2009, right after a 6-inch, noisy deluge, I stopped by this very place and heard, to my astonishment and delight, the sheep-bleating calls of spadefoots. (Here’s a link to their calls: srelherp.uga.edu/anurans/scahol.htm) For reasons of amphibian security, I can’t tell you where this place is, but historical records show that a location near this spot hosted spadefoot breeding activity in the past.

I can tell you that I never heard anything like the S. holbrookii concert I listened to—for one evening—in 2009. I haven’t, despite rainfalls that seemed amenable to waking subterranean toads, heard anything like it since.

Until May 1, 2014.

It was as fine a birthday gift as I could have asked for, and after I made some recordings—it was too wet still for photography—I sent them off to my good friend Dave Skelly, an eminent Yale ecologist (and the just-appointed new director of the Peabody Museum of Natural History). Dave and his grad student Max Lambert, who is clearly bound for a fine career as a biologist, arrived at our house the following night, and though the chorus by then was much weaker, the fact that the spadefoots were calling at all exerted an animal magnetism on Max. Even without waders, he sloshed into the chilly water and after one failed attempt at capture, he succeeded beautifully on his second try.

“Awesome, Max!” said Dave with child-like glee, as his acolyte returned, spadefoot in hand. My wife Pam and I, along with Dave and a pretty wet but ecstatic Max, gathered round the exquisite amphibian, which looked very prehistoric, to observe, marvel, take notes, and photograph. The spadefoot, for his part, relaxed and seemed entirely unflustered at being held.

“They’re very mellow amphibians,” said Dave, noting that spadefoots are actually fairly common in the south but then peter out in this, the more northern part of their natural range. Here, as is often the case, the cause of their very limited numbers is development. “These guys seem to thrive and aim to live in places where nobody else goes. They may even avoid other amphibian species,” said Dave. “That may give them a measure of protection, since they’d have, in ponds that had just filled, no competitors and no predators, except tadpoles of their own species.”

The young spadefoots would just have to be able to get out of these very ephemeral ponds fast, which is something they’ve evolved to be able to do. But such amenable habitats are in short supply and disappearing quickly. Change is not always good, Dave noted, especially when “you change things and the toads no longer have other options.”

For now, these remarkable animals don’t need our magic to survive, even thrive. Indeed, all they require is our benign neglect, coupled with their own magic, and a stretch of wet weather. Hagrid would certainly counsel that staying away is the best method for caring for these magical creatures. I concur, but from time to time, I’m going to stop by to watch, from a safe distance, their progress.

 

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