January is a rather strange time to be thinking about frogs in Alaska. However, I crossed a small open creek while traveling with the dog team a few days ago and frogs came to mind. As a kid growing up, I used to catch frogs and tadpoles from a pond near our house. I'd bring them home to live in jars and tubs for a week or so. I never could figure out why they wouldn't eat mosquitoes out of my hand. The ponds where these small frogs lived in the early spring always dried up and the frogs were gone. Occasionally I'd find one hopping in the woods during the summer but by moose season they were all gone. Where did they go?
Our Alaska frogs are wood frogs. They don't go anywhere in winter. They stay in the leaf litter on the ground and freeze solid. The little frogs' hearts stop and they quit breathing. Spring comes and they warm up and get on with life. That's a lot cheaper than a trip to Hawaii. They can tolerate freezing and thawing many times throughout the winter without damage.
Wood frogs are one of the most freeze-tolerant animals on Earth. They prepare for the winter by employing special ice nucleators that actively seed ice formation in their bodies. That way they can begin to freeze right at 32 degrees and get solid a bit more slowly. Frogs also build up glucose in their cells, which acts as an antifreeze to keep the insides of the cells from freezing. In the bodies of most vertebrates, icing forms crystals in the cells, puncturing and destroying them; hence the major damage caused by frostbite.
More than 60 percent of a frog's body water freezes. All of it is solid except for the insides of the cells. There is no blood movement. This is suspended animation. We don't know how they trigger their bodies to come back to life. We don't know how their bodies can tolerate blood sugar levels 100 times higher than normal. These little wood frogs even have their eyes freeze solid.
However, just hours after spring temperatures rise above freezing and the ponds begin to melt, wood frogs come to life and begin to make more little frogs. They breed anywhere there is water. Meltwater ponds, roadside ditches and even tire tracks that hold standing water for a short time will work for these resilient critters. Once the tadpoles grow legs, they leave the water and live on mosquitoes and other insects until freeze-up.
In the Paxson area, spring comes late and the freeze is early. Frogs are active for just over three months. If one lives for a couple years, how long is it really alive? They don't have much time to grow!
The farther north one goes, the smaller wood frogs are. In the Brooks Range I have found adult frogs that were just over an inch long. The Anchorage area has frogs three times that big. They range as far south as Ohio. I have found them along the Yukon River. I discovered one accidently while trapping beaver in February.
I was making a beaver set on a frozen pond when I chipped into the ground under the snow where I thought there was water. Up came a chunk of frozen muck with a frog sticking out. That was in the '70s and I puzzled over it for quite a while before I got to a library. It seems that winter is not such a strange time to think of frogs.
The first year I was the trail coordinator for the Yukon Quest, I put up a funny sign to entertain tired mushers along an open lead on the Yukon River. The sign said, "watch out for frogs!!" Maybe I wasn't so far off after all.
John Schandelmeier is a lifelong Alaskan who lives with his family near Paxson. He is a Bristol Bay commercial fisherman and two-time winner of the Yukon Quest.