An End to Hibernation

End of Hibernation: The Dunk

Bullfrogs hibernate during the winter so their metabolism slows significantly and they aren’t very active but they don’t bury themselves in the mud the way a turtle might. Many bullfrogs at Ridgefield found their hibernation cut short this winter by the herons and egrets and bitterns that worked the shallow channels and ponds of the refuge.

This egret in particular was just walking up and down one such channel, avoiding a great blue heron doing the same, striking at bullfrog after bullfrog, following a familiar process between catching the frog and eating it. First, the frog would be dunked quickly into the water, as shown above. Next, the egret would spin the frog rapidly, presumably causing massive internal injuries to the frog, as shown in the following two pictures. In the first picture, the egret has closed the nictitating membrane in its eyes, a transparent third eyelid that protects the eye from damage while still allowing the egret to see, as water spins off the frog and its clawed feet flail about, while in the second picture the membrane has been retracted.

End of Hibernation: Spin Cycle No. 1

End of Hibernation: Spin Cycle No. 2

Then the egret would toss the frog into the air, catching it in a different place on its body, and either repeat the process again if it caught it by a leg, or perhaps crush it in its beak if it caught it by the body. This would happen multiple times until I gather the frog had died or given up fighting, although with the egret constantly keeping the frog moving it was hard to tell exactly when or if the frog itself stopped moving.

End of Hibernation: Throw & Catch

The final step was to position the frog head first in its beak and swallow it whole. Bullfrogs are voracious predators and, as they aren’t native to the area, have had a big impact on some of the other small creatures in the ponds and sloughs. However I’ve seen the bullfrogs themselves become prey for the larger predators of the refuge, including not just egrets and herons and bitterns but otters, raccoons, and grebes.

End of Hibernation: The End

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