A Plague of Frogs or a Jubilee of Toads

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Figure 1. The swarm of newly metamorphosed eastern spadefoot toads that emerged on the shore of Shol Pond on 2 October 2000.

According to the Book of Exodus, the Lord punished Pharaoh by sending a plague of frogs out of the river, vast hordes of frogs, across all of Egypt from one border to the other until the people were overwhelmed by frogs. How many frogs constitute a plague? How many frogs does it take to physically overwhelm the land? One recent emergence of eastern spadefoot toads, Scaphiopus holbrookii holbrookii, in Florida may shed some light on that question.

Unlike the biblical plague, they did not swarm into houses, bedrooms, beds, mixing bowls and ovens, but the mob of newly transformed eastern spadefoot toads that emerged from a small wetland called 'Shol Pond', located in the Riverside Island area of the Ocala National Forest, Marion County, Florida, on 2 October 2000, was so immense as to overwhelm everything in sight of their nursery pond (Figure 1).

The toads physically and visually blanketed the northern shore of 'Shol Pond' as effectively as nylon carpet (Figure 2).

Although the area of emergence measured approximately 375 ft2 (35 m2) or 15 by 25 feet (4.5 by 7.5 m), the baby toads were so numerous and so close together that, save for a clear strip of sand along the water's edge, it was impossible to walk anywhere for fear of crushing the toads. In most places it was physically impossible even to touch the ground with the tip of a finger without first brushing the toads aside (Figure 4).

'Shol Pond' is a small, elongate, shallow depression surrounded by a beautiful forest dominated by longleaf pines and wiregrass. The U.S. Forests Service maintains the lush, open, park-like conditions of the forest around the pond with prescribed fire. Without regular fire to maintain the pine forest, hardwoods (primarily oaks) would eventually dominate and the wire grass and myriad other plant species forming the lush green groundcover of the forest floor would disappear under the smothering shade of oaks.

The miniscule toads, about the size of raisins (Figure 3), had recently completed their metamorphosis from egg to tadpole to toad, and were beginning to disperse into the uplands surrounding the pond. Because the toads spend most of their lives in the uplands a long distance from the breeding pond, maintaining the forest in as natural a state as possible is key to preserving the toads and the many other species that inhabit the longleaf pine forest.

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Figure 2. The carpet of newly emerged eastern spadefoot toads, Scaphiopus holbrookii holbrookii

We estimate the horde contained in excess of 1,000,000 of the 1/3 to 1/2 inch (0.8-1.27 cm) long, newly transformed, spadefoot toads (Figure 3). To a couch potato who dislikes the out-of-doors and wildlife, the emergence could only be described as a 'plague' of toads. To a herpetologist or lover of nature it was not a pestilence, calamity nor a nuisance. It was a thrilling spectacle. To Archie F. Carr, Jr. (1994:22-39), it might have been a 'jubilee.'

The word 'jubilee' comes from ancient Hebrew and originally referred to the twice a century celebration that was marked by the freeing of slaves, cessation of farming for a year, restoration of land to its former owners, and the blowing of rams horns. In modern usage, 'jubilee' signifies a periodic special celebration or a season of celebrations. That is the reason the citizens of Daphne, Alabama, call the massive assemblage of crabs, eels, flounders, and other fishes that occurs from time to time in the shallow waters on the eastern shore of Mobile Bay a 'jubilee.' When winds from the east are mild enough to push the surface waters without whipping up waves, they set up a circulation in which the surface water moves west before the wind and the deeper water slowly flows back eastward along the bottom to replace the surface layers. Waterlogged detritus that washes in from rivers at the head of the bay lies on the bottom decaying and giving off noxious gases, and as a consequence the deep water has little oxygen in it. Fishes and crabs retreat before the anoxic barrier flowing up from the bottom and soon find themselves in the shallows of the east bay. That near stranding provides a celebratory occasion for the people of Daphne to come together to harvest and feast on this infrequent cornucopian abundance of seafood.

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Figure 3. Close-up of the newly metamorphosed eastern spadefoot toads, Scaphiopus holbrookii holbrookii

Carr (1994:25) points out such unusual congregations of aquatic animals occur at other sites and it is appropriate to apply the term 'jubilee' to them as well.

Carr (1994:25-31) tells of another jubilee, the periodic mass assemblage of tens of thousands of little fishes, golden topminnows, gambusias, elassomas, salamanders, sirens, and crayfish in the water that spilled through culverts under a road in the Wacahoota Hammock on its way to Ledwith Lake in northcentral Florida. Carr (1994:27) says the aquatic critters were so abundant, "It was hard to think of a way to get good counts of the teeming jubilee animals. The water was too fast, the bottom too rocky, the different species too spottily and shiftingly spread about the basin, and the composition of the pool too changeable from day to day. But one day we made three short hauls with a little six-foot common-sense seine and laboriously counted out the catch. There were 7,505 animals in our bucket. Seventeen species of fishes were there, and in numbers far higher than normal for the stream. Of these, seven kinds made schools so dense that they hid the bottom or even bolstered their own upper tiers above the surface of the water. These most abundant fishes were in their most usual order of abundance; mosquito fish, golden topminnow, pygmy sunfish, blue-spotted sunfish, flag-fish, lined topminnow, and red-fin pickerel. The remaining ten species were less numerous, but there were still far too many to be in such habitat. The most abundant animal that night was the crayfish Procambarus fallax. We counted 2,084 of these." Five of these Wacahoota jubilees were observed before upstream modification of the stream ended the phenomenon.

Though it was a more or less permanent feature of the spring and not a periodic event, Carr (1994:33-37) identified the throngs of fishes in Homosassa Springs on Florida's west coast as yet another jubilee. Carr (1994:34) describes the scene he observed from a shaky old, narrow, dock at the spring, "There were orderly swarms of saltwater catfish-both gaff-topsails and sea catfish-pinfish in hundreds, schools of anxious mullet, a dozen big speckled sea trout, and three burly redfish. Down deep in the main conduit I could see mangrove snappers resting, and there were small bands of big sheepshead prying about the rocks. A half-grown tarpon kept charging aimlessly back and forth through schools of smaller fish, which hurriedly opened as he passed and quickly closed behind him; and back near shore under a raft of drift and water lettuce a row of big snooks lay in the gloom like bigmouthed logs. Beside these migrants from the Gulf there were a few big largemouth bass, multitudes of bluegill bream, little schools of stumpknockers, and a gang of longnose gars. There were other kinds without doubt, but those are the ones I remember seeing from the quaking platform of the rotting catwalk." Carr (1944:37) speculates about lesser gatherings of fishes in other Florida springs and lumps them together as jubilees as well.

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Figure 4. The crowded mob of newly emerged eastern spadefoot toads, Scaphiopus holbrookii holbrookii

Carr (1994:32) also recounted as a possible jubilee William Bartram's (1996:117-118; Van Doren 1928:118-119) encounter in 1773 of a gathering of alligators arrayed across the mouth of Lake Dexter where it joins the St. Johns River. The close phalanx of alligators formed a fence-like barrier that allowed them to easily snatch up fish that tried to swim through their ranks. Carr observed, "This spectacular aggregation of alligators was also baited up by teeming fishes. The conclave, the fish part at least, may qualify as a real jubilee. The congregation was produced by the upstream movement of many kinds of fishes traveling together, and its late stage occurred in a narrow pass that connected one body of water to another." The multitude of fishes moving through that spot might qualify as a jubilee, but the alligators were there to join forces with their colleagues in a cooperative effort to catch fish, a phenomenon well-known in crocodilians.

The overwhelming swarm of eastern spadefoot toads recorded here was the result of torrential rains delivered by Tropical Storm Gordon that broke a drought and attracted adult spadefoots to the newly filled 'Shol Pond' where they bred and laid their eggs. Eastern spadefoot toads are explosive breeders that are drawn out of their burrows and into wild mating aggregations by torrential downpours that dump several inches of rain that in a short period of time rapidly fills the breeding ponds.

Spadefoot toads are adapted to breeding in temporary ponds that may dry up and disappear in a few weeks, so their eggs hatch in 1-2 days and the tadpoles feed incessantly and metamorphose into tiny toads in as little as 2 weeks. Eastern spadefoots breed only in the most short-lived wetlands and until they are suddenly filled, most of their breeding ponds appear only as dry depressions in the woods. Most permanent ponds develop a full complement of fishes, aquatic insects and other predatory species. However, if the pond dries up these aquatic predators die. Because eastern spadefoot toads usually breed in ponds that only hold water for short periods of time, the tadpoles have relatively few competitors or predators.

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Figure 5. The Shol Pond jubilee emergence of eastern spadefoot toads.

To produce the swarm of more than 1,000,000 baby toads, hundreds of adult male spadefoot toads had to be drawn to this breeding pond where they attracted egg-laden females with nightly serenades. Together they populated the pond with individual clutch masses of 2,000 or more eggs stuck to the submerged vegetation. It seems reasonable to assume that the spectacular swarm was the product of egg clutches laid by more than 500 females.

As protection against predators, spadefoot tadpoles typically remain together in dense schools. The schools move around the shallow edges of the nursery pools feeding on algae and other vegetation. If this occurs in the early spring, the surface of the pool may become covered with a yellow scum of pine pollen that is ravenously eaten by the tadpoles. The pollen packs the gut of each tadpole until it shows bright yellow through the body wall. The massive schools of bronze-colored tadpoles flowing around the pond like a giant amoeba were spectacular.

Only one species, the eastern spadefoot toad, Scaphiopus holbrookii holbrookii, was involved in this spectacle, and only the tadpoles are truly aquatic, the young toads being newly terrestrial. Nevertheless, Archie Carr may well have considered this assemblage of toads to be another jubilee.

To paraphrase Carr (1994), "To even the most detached or town-loving observer jubilees are a wonder. To a zoologist who fancies himself familiar with the behavioral norms of the little animals involved, they are sensational." Jubilee or plague, this assemblage of newly emerged eastern spadefoot toads was a once in a lifetime spectacle.

Literature Cited

Bartram, W. 1996.
Travels and Other Writings. Thomas P. Slaughter, Editor. The Library of America, New York. xv + 701 p.
 
Carr, A.F., Jr. 1994.
Jubilee. pp. 22-39. In: Majorie Harris Carr [ed.], A Naturalist in Florida. Yale University Press, New Haven. xviii + 264 p.
 
Van Doren, M. 1928.
Travels of William Bartram. Dover Publ., New York. 414 p.

Authors: F. Wayne King, Florida Museum of Natural History, Gainesville, FL 32611-7800, U.S.A. and Steve A. Johnson, Florida Caribbean Science Center, U.S. Geological Survey, 7920 NW 71 Street, Gainesville, FL 32653, U.S.A.

Suggested Citation: F. Wayne King and Steve A. Johnson. 2002. A Plague of Frogs or a Jubilee of Toads. 8 p. [Online] Available at: http://www.flmnh.ufl.edu/herpetology/links/plague-frogs-or-jubilee-toads