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Frogs on ice

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This time of the year I get into the habit of checking for the first signs and sounds of the spring peepers and wood frogs in local ponds. In our region, the last week of March through the first week of April is a great time to hear those first emerging for the season. Spring peepers call for several weeks, while wood frogs are considered “explosive breeders”: they breed within a short period of time after they begin calling at a particular pond. Within a few days after hearing calls their calls, the only evidence of breeding are egg masses, usually found clustered together. Both species start calling and breeding on mild days when the temperature gets into the 50s or warmer.

Breeding wood frogs in the open water of this pond were calling for females to breed with. The female lays her eggs in a mass as the male fertilizes them. Wood frogs breed very early in vernal pools and ponds; the tadpoles can hatch in a week and are froglets by June, which is important, as many of these ponds dry up during summer. 

It was a mild day when I went to this particular pond early last week. This pond holds ice longer than any other in the area, and I had already checked it twice without hearing any frogs. This day was sunny with temperatures in the mid-60s, but the pond had only a small shore area that was free of ice. At first, I didn’t see or hear anything, but then I saw some small objects on the ice. Upon closer inspection, they turned out to be wood frogs sitting on the ice. No matter how warm the air temperature is, ice will never be any warmer than 32 degrees.

After a few minutes, I saw a few of the frogs on the ice start to move. They did not hop like frogs usually do. Instead, they slowly extended their rear legs, pushing themselves on their bellies toward the small patch of open water. After a push or two, they took a few minutes of rest.

I took some photographs of a frog close to the shore. On a hunch, I went to pick it up, expecting it to try to escape, but to my surprise, it did not move. Gently, I picked it up and placed it on the ice in the sun, pointing it toward the open-water area where the rest of the “ice frogs” were headed. Being cold-blooded, it was the same temperature as its surroundings; it was one cold frog! It’s likely that I caught these frogs just after they emerged from their hibernation areas, typically leaf litter on holes or hollows in the ground. A wood frog can withstand freezing temperatures during the winter because its body starts producing glycol as cold weather approaches.

All at once, as if someone turned on a stereo, the sound of a dozen or so calling wood frogs filled the air. All the males calling had already made it to the ice-free patch of water before I got there; they were calling to attract females in order to breed. Several frogs appeared on the water’s surface. The frogs on the ice did not call, but continued their slow progress across the ice. Until their body temperature warmed up a bit, they could move only so fast on their quest to reach the open water and find a mate to breed with.

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