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Too many frogs

March is the season for the so-called "movement nights" of the crawfish frog. Particularly on warmer nights, under the protection of rain, the frogs move from their subterranean dwellings where they have lived the whole previous year to breed in ephemeral wetland pools. They seem to have a strong instinct to return to the ancestral ponds in which they were born. The males move first, calling from their burrows and then forming choruses in the ponds where they gather, and a deep snore rolls across the prairie. They wait for the females to emerge and come to the ponds themselves. Sometimes staccato grunts can be heard as the males fight each other during the breeding season.

At Big Oaks, the Crawfish frog breeding season formerly began around mid-March (St. Patrick's Day), but has become earlier each year, now being more towards the beginning of March. It generally lasts a few weeks, depending on how many nights there are with favorable weather. As the males clasp the females in amplexus, they fertilize the emerging egg masses, each of which contains some 5,000 to 8,000 eggs. In a few weeks they will develop and hatch into tadpoles. This whole time they are incredibly vulnerable to predators, including newts, salamander larvae, green frog tadpoles, fish, and snapping turtles. Losses throughout the frogs' development are very high, and most never make it.

We have been feverishly working on the crawfish frog project the last month, including searching for egg masses, transferring egg masses, rearing tadpoles in cages, and listening for calling at night. We have had major setbacks: one pond began to leak around the water control structure and many eggs were killed by drying out, although we have since repaired the leak. We drained Karns pond in order to reduce the load of Perkinsea parasites which have been causing mass die-offs of tadpoles, but the large population of crawfish frogs still laid almost 50 egg masses in shallow puddles in the basin, puddles which will not last through the developmental season. During the heavy rain the past few weeks, green sunfish managed to enter ponds that had dried last fall, potentially causing massive damage. These events happen every year, but the crawfish frog has remained resilient.


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