Help Frogs Hybernate
What will these dead leaves do for the fish? Nothing good. The decomposition of leaves underthe ice will use oxygen, and that’s bad for fish. Let’s examine what wild frogs do when winter closes in. Bullfrogs, green frogs, leopard frogsand some other frogs squirm down deep through the layers of dead leaves and debris. Therethey sit. I cleaned and emptied one and filled it with fresh water. Into the other I dumped a bushel ofdead leaves. Then one cold winter day I checked the temperature of the ponds with aprobe-type thermometer. The problem for most frogs in ornamental ponds isn’t a lack of oxygen or a potful of mud. A”clean” pond bottom is the problem. A clean pond is inhospitable to a frog, especially in winter. That’s because the watertemperature can’t stratify. That is, the bottom layers aren’t much warmer than the top. A deeper pond is better. In the piedmont and coastal plain, a foot deep might be enough. Inthe mountains and colder areas farther north, two or three feet is better. When the water gets too cold for them to move, they’re helpless. When spring comes and theirworld warms, they swim to the top, get a breath of air and become active again. No one system is good for everything. So manage your fish ponds and frog ponds differently. But if you let leaves and debris accumulate, you’ll provide a better winter habitat for yourfrogs. That doesn’t mean all your frogs will survive, but it definitely improves the odds. In the October issue of Pondscapes Magazine, Mike Mullen of Kansas City, Mo., wrote abouthis problems in bringing frogs through winter. Here’s an experiment I did one winter to gather data on this frog-in-winter problem. I had twoidentical plastic ponds, about a foot deep, in the front yard. Mike placed a bubbler in the pond to add oxygen. But it didn’t seem to help. He put acontainer of sand on the bottom for the frogs to hibernate in, but they didn’t burrow into it.They just sat on the bottom and chilled into immobility. Winter hibernation is hazardous to a frog’s health. Some die. But then, every day is hazardousif you’re a frog. To live a year is to be exceptionally lucky. With the arrival of chilly fall nights, I’ve been getting calls from ornamental pond ownerswondering what to do for their frogs and turtles during winter. The temperature at the top of the leafy pond was the same, just above 32 degrees. But as Ipushed the probe deeper I recorded higher temperatures. At the bottom, it was a bit over 40degrees. I broke a little hole in the ice of each pond. The ice was about an inch thick on the clean pondand just a skim, about an eighth of an inch, in the leafy one. The clean pond was just slightlyabove 32 degrees from top to bottom. Is there an easier plan to get frogs through the winter? There is. Last year he feared Freddie, his favorite bullfrog, would suffer a similar fate. So he broughtFreddie into an indoor pond for the winter. That’s one solution, but it means extra workbecause, among other things, frogs need live food. He noticed that the frogs in his pond didn’t hibernate successfully. When spring arrived, hefound dead frogs in it. To help turtles hibernate, provide the same dead-leaf habitat. If you’re a neat type and want clean water right to the bottom, this doesn’t bode well for yourfrogs. The layering of leaves on the bottom slows down water mixing and keeps the temperaturewarm enough for hibernation.