Ben StegengaViews:
The spring field season is in full swing now. Indigo snake surveys have been completely wrapped up, and like most of our research staff, my last six weeks have been almost completely consumed by Spotted Turtle and wetland inventory fieldwork. As I settle into my Florida hotel room this evening after another long day of dip-netting wetlands, I think about what I’d like to feature in this month’s article. Since all my current fieldwork (aquatic trapping, dip-netting, etc.) is dependent on rainfall and full wetlands, I keep coming back to a series of observations I made in a dry pond basin back in December while doing some routine data logger downloads.
If you’ve been following Fieldnotes for a while, you may remember a video from last year where I talked about putting in PVC hydrology wells and data loggers in flatwoods salamander ponds. Since their deployment, it’s been my job to revisit those wetlands about every four months to download the data and conduct any needed maintenance on the wells. My last site visit was in December, and besides having to dig up a couple of wells to remove sediment, the week had been pretty uneventful. Fall and early winter of 2024 had been extremely dry in southern Georgia and the Florida Panhandle, so almost all the wetlands were bone dry. One of my last wetlands was a pond that had historically supported Reticulated Flatwoods Salamanders, but due to fire suppression, it’s no longer a suitable breeding pond. Cypress and hardwoods have created a full canopy, shading out almost all herbaceous vegetation that is critical for salamander nest sites and larvae. Instead of swishing through a sea of grasses on my trek to the center of the pond basin, my footsteps softly crunched in the dry cypress needles and leaf litter. I spotted the pink flagging tape hanging from a young sweet gum, indicating I was close to the well. We typically place our wells in the lowest point in a wetland, however, we decided against that in this pond. That’s because at the very center of this pond, an alligator had excavated a pit and burrow. Since the basin was completely dry, this “gator hole” stood out like an anole’s dewlap, but when a pond is full, the dark tannin-stained water can conceal it completely. That is, unless you literally stumble into one, which is what we did last summer while installing this PVC well.
Much like Gopher Tortoises or American Beavers, American Alligators are considered ecosystem engineers. They create large mound nests for their eggs, they wallow out pits that reach down to the water table, and they excavate burrows into the banks of ephemeral wetlands. All of these features benefit other wildlife species by providing nesting habitat, foraging opportunities, shelter from the elements, or access to water. Alligators construct pits and burrows mainly so they can thermoregulate during extreme weather and maintain access to water during seasonal dry spells or drought. And since this pond basin was now completely dry, the gator den was now a small oasis, providing the only accessible surface water in the area.
I walked over to the well, set down my backpack, and retrieved the data logger to initiate the download. I glanced over at the murky pool of water and noticed a familiar orange and brown pattern among the cypress knees and exposed roots. It was a small Banded Water Snake, less than a foot long and undoubtedly born just a few months prior. It’s always cool to see snakes active in the winter months, and I hadn’t seen many herps all week, so I inched closer to admire him. I soon noticed two frog feet sticking out of his mouth and realized he was in the middle of securing a valuable winter meal. He also had another food bolus in the middle of his body, so this wasn’t the first frog he had caught that day. I watched him finish his meal, but he didn’t seem comfortable with an audience, so he nervously retreated back into the labyrinth of exposed cypress roots.
It’s always exciting to see a predation event in the wild, so I was quite happy to end my day on that note. But before I could turn my attention back to my task, I noticed a few frogs sitting along the edge of the pool. I had just assumed the legs sticking out of the snake’s mouth had belonged to a Southern Leopard Frog or Green Frog, but that’s not what I was looking at. “Whoa…River Frogs?!?” Sure enough. As I scanned the water’s edge, I counted about half a dozen newly metamorphosed River Frogs. Thankfully, River Frogs are still somewhat common in this part of their range, but I also never expect to encounter them without specifically seeking them out. As their name implies, River Frogs are most often associated with large blackwater rivers, creeks, and their associated oxbows, sloughs, and swamps. There was a creek drainage less than a kilometer away, so it made sense for them to be in the area, but this was the first time I had seen them using a completely isolated ephemeral pond.
Just moments later, a series of ripples caught my eye. It took a few seconds for my brain to register what I was seeing. Dozens of tadpoles were ascending to the surface of the water, gulping air, and then diving back down into the murk. This is a common behavior among many tadpoles, especially in water with low levels of dissolved oxygen, because it allows them to supplement their oxygen intake. I immediately ran back to my truck to grab a dipnet. It was now late afternoon, and I knew deer hunters were probably climbing back into their stands at that very moment, so I needed to wrap things up soon. I rushed back to the gator hole and swept my net through the cloudy water. To my amazement, I pulled up about 50 large River Frog tadpoles. River Frogs have one of the largest tadpoles of any North American frog, sometimes reaching 15 cm (6 inches) in length. Their size, coupled with those vibrant red eyes and cream-colored tails, outlined in black, make them very distinct. They also form large schools that can number in the thousands. Due to how many I netted in one swipe, I estimated there had to be at least several hundred tadpoles in this pool. I pushed my net back under the bank into the burrow section of the den and was unable to feel the back. There’s no telling how many tadpoles this little oasis held. Like some other members of their genus, River Frog tadpoles require long periods of time to develop, and they may take over a year before undergoing metamorphosis. That means this might not be the only dry-down event that these tadpoles have survived due solely to this gator hole. Without it, I don’t see how any River Frog tadpole could survive in this pond.
I snapped a couple more tadpole voucher shots, released them all back into the pool, and finished filling out the datasheet for that wetland’s data logger. That evening, I had a long drive home, and after I had secured some dinner and caffeine for the road, I had plenty of time to reflect on my observations. I think all too often, people think of creatures like alligators as these one-dimensional monsters that only interact with other wildlife by eating them, and that couldn’t be further from the truth. Humans love to villainize predators without really understanding how they fit into the web of life. Just like the gray wolves in Yellowstone, the presence of large crocodilians has an effect on every trophic level within their ecosystem. Whether it’s by direct predation, wetland modification, nest building, nutrient cycling, or even seed dispersal, alligators shape the plant and animal communities around them, and ultimately boost biodiversity. I think my brief observation demonstrates that well, but it’s still only a brief snapshot of one aspect of this alligator’s biology. This alligator den was likely supporting more than just tadpoles and a single water snake. There could’ve easily been crayfish, small fish, aquatic invertebrates, turtles, or aquatic salamanders out of sight beneath the bank. Terrestrial animals might also be drawn to the pool when in need of a drink, and the benefits would extend to any predators that might be attracted to such a concentration of life, such as snakes, raccoons, otters, foxes, barred owls, herons, egrets, and kingfishers. Now, if you imagine similar scenarios replicated all over alligator range, likely hundreds of thousands of times, you can start to see just how important alligators are for our southeastern landscapes and all the species that live alongside them.
