Voiceless frog discovered in Tanzania
Researchers found the amphibian while looking for another feared extinct
Peer-Reviewed PublicationIMAGE: AN INTERNATIONAL TEAM OF RESEARCHERS DISCOVERED A NEW SPECIES OF SPINY-THROATED REED FROG WHILE CONDUCTING AN AMPHIBIAN SURVEY IN TANZANIA'S UKAGURU MOUNTAINS. view more
CREDIT: CHRISTOPH LIEDTKE
Researchers discovered a new species of frog in Africa that has an unusual trait: it’s completely silent.
The Ukaguru spiny-throated reed frog does not croak, sing or ribbit. Found in Tanzania’s Ukaguru Mountains for which it is named, Hyperolius ukaguruensis is among the few frogs around the world that do not vocalize to other frogs.
The new species belongs to a group of “spiny throated” reed frogs, which true to their name have tiny spines on the male’s throat. Since they can’t rely on sound to recognize members of their species, they might use spines instead.
“It’s a very odd group of frogs,” said Lucinda Lawson, a conservation biologist and assistant professor of research at the University of Cincinnati.
“The male frogs don’t call like most other frogs do. We think they may use the spine as something like Braille for species recognition,” Lawson said. “Without a call, they need some other way to recognize each other.”
This group of frogs has only a few species, found in small populations that make them rare and at risk of extinction. Finding a new member of this group is a major win for conservation, Lawson said.
The discovery was described in the journal PLOS ONE.
Lawson in 2019 led an international team on an amphibian search of the Ukaguru Mountains, where scientists have conducted at least seven previous surveys. They were hoping to find the beautiful tree toad, Churamiti maridadi, an amphibian that has only been observed twice in the wild in this same forest and is feared extinct.
“Our hopes were not very high. We knew the odds were stacked against us,” said study co-author H. Christoph Liedtke, a postdoctoral researcher with the Spanish National Research Council.
Researchers scoured undisturbed streambanks both day and night, documenting their search with handheld global-positioning satellite receivers. They looked under logs and in tree holes in an area of forest used by beekeepers, poachers and small-scale loggers.
They also set pitfall traps made of plastic buckets buried at ground level to catch amphibians that hide under the leaf litter. Researchers consulted with local foresters and distributed photos of the toad to nearby residents hoping someone — anyone — might have seen it.
While researchers never found the toad, they came across a locally abundant population of reed frogs unknown to science.
“Time spent looking for the beautiful tree toad yielded unexpected results. It was a fantastic finding that made the effort well worth it,” Liedtke said.
The newly discovered reed frog joins a family of nearly 200 species in the genus Hyperolius. Lawson said they immediately recognized they had found something special.
“With any Hyperolius, I can probably tell by looking at it whether it’s new or potentially new,” Lawson said.
“Immediately it was clear that it was a spiny-throated reed frog. But this one was a golden, greenish brown instead of the green color found in the other species,” Lawson said. “Sometimes color variation doesn’t mean anything, but it might here.”
A combination of genetic and genomic analyses confirmed the frog was distinct from other members of Hyperolius. Researchers also identified its closest evolutionary relation, Hyperolius ruvuensis, another species that is critically endangered and is likely extinct.
Measurements found that the frog has unique body proportions, with smaller eyes in relation to its head than other spiny-throated reed frogs.
Describing a species is the first step toward protecting it, particularly in increasingly fragmented forests like those in the Ukaguru Mountains, Lawson said.
According to the study, the newly discovered frog could be of high conservation concern.
“The Mamiwa-Kisara North Forest Reserve is a T-shaped remnant forest,” Lawson said. “It has a lot of edge effects from people cutting firewood. There are all sorts of pressures on this forest. It’s easy to cross the whole thing in just a few hours of hiking.”
Knowing how many species exist and where is critical to conservation, Liedtke said.
“The Ukaguru Mountains are part of the greater Eastern Arc Rift, a fascinating cradle of biodiversity, with many species endemic to single mountain blocks,” Liedtke said. “The fast population growth in Tanzania means that the mountain forest habitats are under growing threats from people.”
Amphibians are especially susceptible to human impacts. Since they absorb chemicals through their skin, they are vulnerable to toxins or changes in water acidity.
“If a bird’s habitat is destroyed, they sometimes can fly to a new forest. But that’s hard for amphibians,” Lawson said.
Having a diverse number of species is important to maintain healthy ecosystems, Lawson said.
“We think about this question a lot: why does one species matter?” Lawson said.
Frogs are part of the food chain. They eat insects and, in turn, are eaten by other animals.
“If this one species goes extinct, nothing much happens. We just lose one more strand in the fabric of the ecosystem,” Lawson said. “But if you keep pulling out strands, the ecosystem becomes destabilized and the fabric unravels.”
Co-author Simon Loader, curator of vertebrates at London’s Natural History Museum, said he was thrilled to help describe a new species. The discovery shows how much more there is to learn about diversity-rich parts of the world.
“We still have a long way to go before understanding what species are there and where they can be found,” he said. “This is particularly the case for the biodiverse-rich submontane forests of Tanzania”
Also contributing to the study were UC biology graduate Erin Siemer and doctoral student John Lyakurwa of the University of Dar es Salaam in Tanzania.
JOURNAL
PLoS ONE
METHOD OF RESEARCH
Observational study
SUBJECT OF RESEARCH
Animals
ARTICLE TITLE
Diversification of spiny-throated reed frogs (Anura: Hyperoliidae) with the description of a new, range-restricted species from the Ukaguru Mountains, Tanzania
A newfound ‘croakless’ frog may
communicate via touch
The animal might use spines on its throat to recognize potential mates instead of calls
Rather than croaking, a newfound frog (Hyperolius ukaguruensis) might use the spines on its throat to communicate via sense of touch.
By McKenzie Prillaman
FEBRUARY 2, 2023
A newfound species of frog doesn’t ribbit. In fact, it doesn’t make any sound at all.
Many frogs have unusual characteristics, from turning translucent to being clumsy jumpers (SN: 12/22/22; 6/15/22). The recently discovered amphibian lacks a voice. It joins a group of seven other voiceless frog species called spiny-throated reed frogs that reside in East Africa.
Instead of croaking, the spines on male frogs’ throats might help their female counterparts recognize potential mates via touch, sort of like braille, says conservation biologist Lucinda Lawson of the University of Cincinnati.
Lawson and colleagues spotted the little frog, only about 25 millimeters long, in 2019 while surveying wildlife in Tanzania’s Ukaguru Mountains. The team immediately recognized the animal, now named Hyperolius ukaguruensis, as a spiny-throated reed frog. But something seemed off.
“It [was] the wrong color,” Lawson says. Most frogs from this group are green and silver, but this one was gold and brown. Some quick measurements to check if the peculiar frog simply had trivial color variations or if it could be a new species revealed that its eyes were smaller than other spiny-throated reed frogs. The researchers agreed: “Let’s do some genetics,” Lawson says.
They ran DNA tests on two frogs that looked like they belonged to the suspected new species, as well as 10 individuals belonging to known spiny-throated species. Comparing the golden frogs’ genetic makeup with that of the others revealed the oddballs were genetically distinct, Lawson and colleagues report February 2 in PLOS ONE.
Each frog species in this voiceless group — including H. ukaguruensis — lives in its own isolated domain of forest. All seven of the previously known species are endangered or vulnerable. This seclusion makes it vital to distinguish species and get them added to the conservation priority list, Lawson says. Then, governments and organizations can begin protecting the region that the new, potentially endangered animal calls home.
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