Winter’s Frog

For herp enthusiasts across the country, these winter months can feel like an eternity. With winter weather in full swing, reptile and amphibian activity can be hard to come by. However, there are a few species of secretive amphibians that make their yearly appearances during cold, rainy weather—you just have to brave the elements in order to find them. Here in South Georgia, we’re beginning to see pulses of amphibian activity triggered by recent rainfall. Eastern Tiger Salamanders (Ambystoma tigrinum) are arriving at their breeding ponds, and we’re just starting to hear full choruses of Spring Peepers (Pseudacris crucifer), Southern Chorus Frogs (Pseudacris nigrita) and Ornate Chorus Frogs (Pseudacris ornata) from swamps, roadside ditches and ponds. But you have to travel a bit further north to find one of my favorite winter amphibians, the Wood Frog (Lithobates sylvaticus).

Wood Frogs have a large distribution, ranging from Alabama to north of the Arctic Circle, and although they can be very abundant through much of their northern range, in the Southeast they are fairly uncommon and limited mostly to the southern reaches of the Appalachian Mountains. Individuals can be tan, salmon, bronze or brown with a black mask behind each eye, and adults are relatively small compared to many other North American frogs. In the Southeast, Wood Frogs can be quite difficult to find outside of the winter months, as they are often more terrestrial than other frogs. They are explosive breeders, and they converge upon vernal pools or other temporary wetlands whose hydroperiods are too short to support fish predators. Their migration is triggered by winter rain, and they can often be seen crossing roads in mass alongside Spotted Salamanders (Ambystoma maculatum) who are also headed to the same breeding pools.

Sometimes Wood Frogs arrive so early that there is still snow on the ground or ice on the water. While this could pose a problem for other species, Wood Frogs have a special adaptation for dealing with cold weather. They can survive cold snaps by literally freezing and thawing with their environment! Their livers produce glucose which gets pumped into the frogs’ cells and prevents them from being damaged as the fluid in their bodies freezes. During this time their breathing, blood flow, and brain activity all stops until temperatures rise and they thaw out again. This incredible adaptation allows Wood Frogs to have an early breeding season, so they can take advantage of wetlands that only stay filled for a couple months out of the year. After laying eggs, Wood Frogs disperse back into terrestrial and riparian habitats were they will forage for the rest of the year.

Although it’s been close to 12 years ago, I can still vividly remember the night I was introduced to the world of Wood Frogs. While out on a winter bird count on a rainy January afternoon, my father heard a distant chuckling chorus. Intrigued by the unfamiliar sound, he followed it to its source—a small ephemeral pool full of calling Wood Frogs. For South Carolina, that was a really good find. So when he returned home that evening with the news, I was eager to get out that night and see these frogs for myself. I armed myself with a headlamp and my film SLR camera and headed off to the spot my dad had described. I knew that area well. My frequent forays into the woods had brought me right past this spot many times before. It was a small elongated depression that ran parallel to a small creek. During most of the year it was fairly dry, and I had paid very little attention to it in the past when I scoured the neighboring stream for salamanders and snakes. But this time it was different. The recent rain had filled the depression with water and brought it to life. The distinct chuckling calls grew louder as I approached, but then they suddenly fell silent as I reached the top of the steep bank. They were on to me, and I still had a thick barrier of mountain laurels to navigate before reaching the water below.

I realized that getting photos of these frogs was going to require some patience. I laid down in the wet leaves with my camera in hand and slowly army crawled down the slope towards the pool. I paused halfway down to the water and turned off my light. I’m not sure how many minutes passed, but it sure felt like an eternity. Finally, a Wood Frog on the other side of the pool began to call again. One by one, the other males chimed in with their courtship songs, and soon I was in the midst of a full chorus. I zeroed in on one of the calling males. He was tucked in the leaf litter at the base of a mountain laurel. I felt like an egret stalking prey, only closing the distance by inches at a time. I tried to use my light as little as possible and only on the dimmest setting. They seemed wary of even the slightest light. Every time he stopped calling, I would freeze and turn off my light until he grew bold enough to vocalize again, and then I would continue to creep forward. Once I finally got within photo range, he stopped calling completely but remained motionless, allowing me the photo opportunity I had been after.

I repeated this process with several other calling males and shot most of a roll of film before the rain returned, and I made the trek back home. I returned later that week in hopes of seeing them again, but when I arrived I was met with silence. The entire breeding event had ended in a matter of days, but they had left the depression filled with scores of cantaloupe-sized egg masses. I periodically dropped by to check on the tadpoles all the way into the spring until the last ones had emerged from the shrinking puddle. I had witnessed the complete cycle of a Wood Frog wetland, and I found myself excited about seeing it all over again the following year. And still to this day, I find myself going back to those tiny wetlands every winter in search of these wonderful little masked frogs.