(CN) — Step along the banks of a small seasonal pond in the southern Mississippi pine forests, and you just might hear one of the rarest sounds on earth.
Many describe it as a deep snore. In fact, it’s the unique, loud and somewhat charming call of the Dusky Gopher Frog. The amphibian species is so endangered that in 2005, researchers estimated that fewer than 50 breeding adults still lived in their natural habitat.
Now, researchers say the frog is seeing a comeback. In late May and early June this year, conservationists released hundreds of adult frogs into habitats in Mississippi.
The work is part of a recovery plan for the frogs, first published in 2015, which each year sees the U.S. Fish and Wildlife Service and other conservationists grow tadpoles into adult frogs, which are then released in the wild.
In 2021, researchers for the first time found specimens that had grown up on their own. “They are naturally breeding now, which is fantastic,” said Jackson Hutchinson, an American Conservation Experience intern who this year helped with the frog releases.
With a historic range between the Mississippi and Mobile rivers, populations of the Dusky Gopher Frog steadily declined during the 19th and 20th centuries. Timber and agriculture took much of the species’ land, while changing weather patterns, disease and predation killed off others.
The last natural breeding population was discovered in 1987, around a shallow pond on federally owned land in Mississippi’s DeSoto National Forest. At the time, no one was confirmed to have heard the frog’s distinct call since the 1950s.
In 2001, the U.S. Fish and Wildlife Service listed the frog as critically endangered. It is still considered one of the most endangered frogs in the country.
As researchers studied the pond in the early 2000s, they realized tadpoles were dying because the pond would dry out before they could reach metamorphosis. Dusky Gopher Frogs are terrestrial as adults, but females lay eggs and tadpoles develop in so-called ephemeral ponds, which only appear during the rainy season. They also need ideal pH, vegetation and temperature conditions.
“Amphibians today are one of the most endangered groups in the world,” said Joseph Pechmann, a biologist at Western Case University who has studied the frogs since he was a professor at the University of New Orleans in the early 2000s.
Ninety-seven percent of longleaf pine savannah in the Eastern U.S. has been altered or destroyed, Pechmann noted — robbing amphibians of their natural breeding grounds. “In my field, all of us are always very interested in helping to save and recover species that are in trouble,” he said. “The Dusky Gopher Frog was certainly one of those.”
In a phone interview, Pechmann said the species had abounded as recently as the 1930s.
Habitat destruction, coupled with the frogs’ breeding patterns, sent population numbers plummeting through the 20th century.
While adult Dusky Gopher Frogs are exclusively terrestrial, females lay their eggs in ponds. Specifically, temporary ponds: In permanent ponds, after all, fish and other predators might eat the eggs.
But temporary ponds also present challenges for the species, most notably in the form of evaporation. “In its natural environment, the Gopher Frog will drop maybe 1,000 eggs, and maybe 2% to 3% might survive to metamorphosis,” Pechmann said. But “often it's zero, because the pond dries too early.”
As the Dusky Gopher Frog hovered near extinction with so little natural habitat available, Pechmann and others had to get creative about ways to save it.
In a partnership involving the U.S. Fish and Wildlife Service, the Nature Conservancy and the Memphis and Audubon zoos, researchers began to “headstart” tadpoles in protected cattle tanks, later transferring them as adults to temporary ponds to begin new populations.
In recent years, the FWS has reared tadpoles in tanks at the Mississippi Sandhill Crane National Wildlife Refuge. They raised approximately 757 tadpoles this season, providing them pH-balanced water, shelter, foliage and supplementary algae wafers as food. By caring for the tadpoles in a protected environment, “we can get survival rates above 80%,” Pechmann said. “So, the frog is doing much better now than it was in the mid-2000s.”
Each Dusky Gopher tadpole grows to about the length of a finger before beginning its metamorphosis into a frog.
Before release, researchers weigh and measure the creatures and insert a tiny tag into each of their left rear legs. The device lets researchers identify each frog, allowing them to assess the health and growth of Dusky Gopher Frog populations. From a single pond where just a few dozen frogs were discovered in 2005, the program has since recorded several hundred other individuals surviving and in some cases reproducing in at least six other locations.
Earlier this month, American Conservation Experience interns Jackson Hutchinson and Megan Spina helped to coordinate the processing and release of more than 500 adult frogs into natural ponds.
Spina, a graduate student who randomly chose the Dusky Gopher Frog as a research topic for a senior-level ecology class, described the work as rewarding. “There are so many species we take for granted. It’s like the tragedy of the commons,” she said. “In my view, we kind of have a responsibility to bring [back] these frogs because we endangered them in the first place.”
For Hutchinson, the frogs themselves were also endearing.“Sometimes if you shine a light on them or startle them, they will cover their eyes with their forearm,” he said as he processed a handful of frogs for release.
Some of the frogs jumped off the table where Hutchinson was measuring them, hopping about around the room.“I like that this is a direct, hands-on endangered species project,” he added. “Rearing and releasing frogs is having a positive effect on them. Going out to release is very rewarding.”
Lessons learned from the program have also been applied to other efforts to reinforce endangered or threatened species elsewhere. Among them: the Carolina Gopher Frog in the Atlantic coastal plain, the Crawfish Frog in Louisiana and Midwest and the flatwoods salamander in the Southeastern United States.
“A lot of what we've learned, with a little bit of modification, would also apply to these other species,” said Pechmann, the frog researcher. “We can say with confidence that headstarting can work and habitat restoration can work.” The reintroduction efforts, he added, had been “a success story.”
After decades studying the Dusky Gopher Frog, Pechmann also couldn’t help but find the species endearing.
“They are solitary and shy and live by themselves, sometimes coming out of their burrows to bask in the sun and wait for an insect to come by,” he said. “They are very chill frogs.”
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