The seasonal pool is about 50 yards from the tree line, surrounded by dormant, tan grass. As the gentle breeze ripples the water, the vibrant green foliage within the pool waves along with it.
It’s a serene setting, and State Herpetologist Nathan Engbrecht with the Indiana Department of Natural Resources (DNR) can identify the frogs calling from within.
“So that high pitched trilling sound that you hear — that's a Chorus Frog, a very small type of tree frog,” he said. “I think I hear a little ‘chuckle,’ which would be a Southern Leopard Frog.”
If all goes well, the loud impressive call of the crawfish frog might return to this pond in 2026 — 39 years after they disappeared.
The Indiana DNR is working to re-introduce this medium-sized frog back into the Angel Mounds State Historic Site. They died off from this location in 1987, and are endangered in Indiana.
Engbrecht and assistant Jason Mirtle are in the middle of this conservation effort.
“Our goal is to kind of move eggs here the next year or two, maybe three years, until we know that the frogs themselves are reaching adulthood and able to lay their own eggs,” Engbrecht said. “So our measures for success in terms of ‘how do we know when they've gotten here,’ is when they can actually mate and start laying their own eggs and they become more self-sustaining.”
Healthy frog or salamander populations migrate to such pools in the Spring, to breed. The DNR is trying to kick-start this natural process, by moving eggs from Greene County in central Indiana.
These frogs will also have local naturalist Mike Lodato to thank if they re-establish themselves. He closely studied the populations and noted when they disappeared, and advised the state on this issue.
“There were several populations in this vicinity in this part of the state,” Lodato said. They were so prevalent in the 1970s, he led guided nighttime listening tours. But then they slowly disappeared over the next decade.
“Most (disappearances) are explainable because of urbanization or highway construction or surface mining, something like that,” he said. “This population disappeared for unknown reasons about 1987.”
Everyone drags full five-gallon buckets with frog eggs from the DNR pickup to the water’s edge. Engbrecht said this vernal pool is actually the original crawfish frog breeding pond.
“So we're back at ‘ground zero’ here in Angel Mounds to put these eggs in. And if this is just the type of wetland that crawfish frogs like to use. (It) dries up in the fall. Fish can't get established, (it) kind of resets. It fills back up in winter and spring.”
To get to this important seasonal pond in the back of the State Historic Site, it’s wise to take an off road vehicle. The ground is wet and it’s a bit of a walk.
The clear cool water is about knee deep. Enbrecht, Mirtle, Lodato and seasonal DNR employee Jackson Schoettle wade out, one bucket at a time.
He said the eggs are actually bunches of circular, soft egg masses. “They're not really like chicken eggs, like you would think. They're soft, as opposed to having a hard shell.”
“It’s like caviar,” put in Lodato.
Engbrecht lifts the jiggly mass of eggs, gently setting it atop foliage just under the water surface. They repeat this in a few different spots of the pond placing a wire cage over them.
“That'll give them a little bit of protection. And once they hatch in probably about a week or two, then the tadpoles will be swimming around the wetland. We'll pull the cages off, and then the tadpoles are on their own for about the next three months. Probably by like, June or July, this thing will start to dry up. And we hope that they can complete that tadpole stage before it dries up. And they did last year. And it just depends on how wet of a spring we have.”
These frogs are about fist-sized and live in and near empty crawfish burrows. They have defined golden or black circles covering their body.
Engbrecht says such a project fits within the mission of the Indiana DNR Fish and wildlife service.
“On a personal level, I really like these frogs, and I'm really hoping to get them back here at Angel Mounds, where they were, in the past.”
This program started in 2022, and is funded by a conservation grant from the Indianapolis Zoological Society.
The frogs are listed as "endangered" in Indiana, "threatened" in several states and according to Engbrecht, a "regional species of greatest conservation need."
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