Monday, April 3, 2017

Eastern Spadefoot Toad - finally!

An Eastern Spadefoot, Scaphiopus holbrookii, floats among the weeds in a recently flooded agricultural field in Athens County, last Friday evening. This small, largely smooth-skinned toad is one of Ohio's most enigmatic amphibians.

I've wanted to observe spadefoots for years, but finding them isn't easy. Populations display an explosive emergence and reproductive cycle - the toads emerge en masse when weather and moisture conditions are just right, and their singing, mating, and egg-laying may all take place in a night or two. Further compounding the difficulties of locating spadefoots is their unpredictability. Emergences might take place anywhere from late March through July.

Laura Hughes knew of a good spadefoot locale in Athens County - one of nine southeastern counties in which they have been found in Ohio. We went there on a very wet night in early March, but nothing - it was probably just too early in the season. But, hot on the heels of a massive thunderstorm that dumped some two inches of rain in the area, we returned last Friday, March 31. Bingo! The secretive toads had emerged in large numbers, and as is almost always the case, we first detected them by the curious call of the males. They sound a bit like sheep bleating, and the call carries for quite some way. Click the video above to hear a recording from Friday evening.

The site is not a natural wetland, but a low-lying agricultural field along the Hocking River. It was planted in corn last year. Heavy rains, and overflow from swollen river waters, inundate the field for short periods. Thus, the site is not high in amphibian diversity - only the most adaptive species seem to occur there. There were many Spring Peepers, such as above.

Many American Toads were also in the waters, with some males singing. This is a pair in amplexus, or the mating "hug" (male on top). I also heard a Green Frog or two, and a few Western Chorus Frogs, but that was about it.

This is what we had come to find, though - the fascinating Eastern Spadefoot. I met Laura on the southeast side of Columbus around 8 pm, and initially we had reservations about the evening's prospects. The temperature seemed to be dropping, and was hovering around 46 F. We felt that if the mercury plunged much lower, it would keep the toads under ground. However, as we moved south, the temperature gradually rose to about 50-51 F and remained there until nearly midnight, when we left. Plenty warm for amphibians.

A spadefoot, showing its wide spread big goggle eyes, and relatively smooth skin, at least for a toad. There are seven or nine species in its family, the Scaphiopodidae, depending on how the taxonomy is interpreted, and all but the species at hand occur in the southwestern U.S. and Mexico.

Eastern Spadefoots apparently spend most of their life underground, thus a thorough understanding of their life history is tough to ferret out. Limited observations suggest that toads probably come above ground more often than is though, at least on wet or very humid nights, but detection is by far easiest during mass mating emergences, when males are vocalizing.

A closeup of the paddlelike hind foot, showing the animal's namesake spade. The elongate hardened dark ridge helps the toad dig efficiently in the sandy soft soils in which they inhabit.

A male, in full bleat. We estimated seeing or hearing at least 75 toads, but given the size of the site and that we covered only a small portion, I'm sure many others were present.

Finally catching up with this amphibian, and bearing witness to the spectacle of a breeding frenzy, was quite a treat. However, the experience raised numerous questions. Where exactly did the toads come from? How far do they wander? What's the primary diet? How many other populations of this highly secretive animal are out there (listed as state-endangered)? And more.

I can think of a number of other seemingly suitable sites for spadefoots in southeastern and southern Ohio. Hopefully, and now with a much better search image, I will be able to check some of them out during this spring and summer's heavy downpours.

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