- A field survey by herpetologists has failed to find any signs of the Mt. Elgon torrent frog in its native Uganda, raising concerns about the degradation of wetland habitats.
- There are 80 to 100 amphibian species in Uganda, but their habitats are being drained to create farmland and livestock pasture, or to build residential areas and industrial parks.
- Many of the country’s wetlands are also affected by water pollution caused by fertilizer and pesticide runoff from both large- and small-scale farming, as well as industrial effluent and sewage from growing urban centers.
- Scientists say it’s important to keep tabs on frogs and other amphibians because their presence — or absence — serves as a key indicator of ecosystem health.
A team of Ugandan herpetologists has just returned from near their country’s border with Kenya. They were searching for a glimpse of a critically endangered frog that hasn’t been recorded by science since 1962.
They didn’t find any sign of the Mt. Elgon Torrent frog (Arthroleptides dutoiti), but they collected other species that thrive in the same habitat — Natal dwarf puddle frogs (Phrynobatrachus natalensis) and Ruwenzori puddle frogs (Phrynobatrachus petropedetoides) — keeping at least faint hope alive that A. dutoiti may still be present in the fast-moving rapids and waterfalls of the Suam area.
The Mt. Elgon torrent frog is small, around 31 millimeters (1.2 inches) long, with half-webbed toes and clearly visible hearing organs. It is listed by the IUCN as critically endangered. Habitat in the frog’s known range around Mount Elgon has been affected by logging, charcoal production, and farming. But there are still suitable streams and rivers inside the national park that straddles the border.
Previous attempts to find this species in its type locality in Kenya were unsuccessful. The team of four Ugandan herpetologists, led by Mathias Behangana, searched new areas on the Ugandan side where no surveys had previously been carried out.
Mount Elgon stands 4,321 meters (14,177 feet) above sea level, the elevation supporting ecosystems very different from those of the plains it rises above. The 1,279-square–kilometer (494-square-mile) Mount Elgon National Park lies mostly on the Ugandan side.
Outside the park boundaries, Bagisu and Sabiny farmers grow maize, millet and sorghum, coffee, and bananas. Here, as in the rest of the country, the population is growing quickly — 3.2% per year, according to a 2018 report on the Mpologoma catchment area within which the missing torrent frog’s potential range occurs.
Amphibians typically need relatively undisturbed wetland vegetation near rivers or other bodies of water. Most of the sites surveyed were along the Suam River, where expanding agriculture frequently extends right up to the riverbanks, and the research team found far fewer species than expected.
There are between 80 and 100 amphibian species in Uganda.
They face a major loss of habitat, as wetlands are drained to create farmland and livestock pasture, or to build residential areas and industrial parks, according to herpetologist Robert Ssekisambu.
Many of the country’s wetlands are also affected by water pollution caused by fertilizer and pesticide runoff from both large- and small-scale farming, as well as industrial effluent and sewage from growing urban centers.
“Amphibians are very sensitive to slight changes in pH or water chemistry in general. This is because of the nature and dependence on water through the various stages of life,” Ssekisambu said.
Other threats, he said, include changes in climate, and diseases such as the chytrid fungus Batrachochytrium dendrobatidis (Bd for short). “This fungus can kill them in masses. Warming may greatly affect species at high altitudes especially western Uganda and Elgon areas.”
Full extent of the threat undetermined
The conservation status of most of Uganda’s amphibian species is believed to be of “least concern,” according to the IUCN Red List. Many are common species, found across large parts of Uganda and beyond. There has been little research to determine their distribution and abundance and so determine their conservation status in Uganda. This survey will contribute to the ongoing Herpetofaunal Conservation Assessment of Uganda, a loose collection of efforts to assess the conservation status of the country’s amphibians and reptiles and improve natural history information for data-deficient species like A. dutoiti.
Strengthening local data collection and deposition is also a useful way to monitor the health of local ecosystems, because the status of amphibian populations is an important indication of the health condition of wetlands and watercourses.
“If they are many amphibian species or many individuals of a particular species in a habitat like a wetland, it may indicate that the wetland is healthy. If there are a few species or none, this may be an indicator of disturbed or destroyed habitat or wetland,” Behangana said.
In the field, Behangana and his team observed and collected specimens from streams and wetlands and interviewed residents and mapped out habitats. A complementary survey of sites inside the national park will take place later this year,
and the specimens collected — along with sound and location data — will be compared with those held at Harvard University’s Museum of Comparative Zoology to see if the Mt. Elgon torrent frog or one of its close relatives is among them.
Why conserve amphibians
Amphibians are ecologically important, and impacts on their habitat are swiftly reflected in changes in population and species diversity. They are mostly predators, acting as primary and secondary carnivores. Frogs and toads mostly eat insects, some of which are crop pests or disease vectors like mosquitoes. They are also interlinked in food chains, often acting as food for other vertebrates, such as pigs, birds, snakes and sometimes even people.
They are also a source of medicine; Behangana says some communities in the Kabale and Kisoro regions of Uganda use clawed frogs (Xenopus vestitus and Xenopus wittei) as medicine for children suffering from kwashiorkor and other diseases of protein deficiency.
Besides providing habitat for many bird and other animal species, the wetlands that support frogs offer a wide range of benefits to communities. They influence rainfall, purify water by absorbing pollutants, recharge groundwater, and help control floods.
Rhoda Nyaribi, the municipal environment officer for the city of Mbale, on the slopes of Mount Elgon, attributes the disappearance of the Mt. Elgon torrent frog and other species to population growth.
“Population is growing every other day and people are looking for land to cultivate, land to construct and even we had some dry spells previously that forced people to move closer to water sources to cultivate,” Nyaribi said.
Jeconious Musingwire, an environmental scientist with Uganda’s National Environment Management Authority, says he is optimistic that such research efforts are a major step in finding this lost frog or “discovering previously unknown amphibian species” in the country. But he acknowledges the fact that amphibians are broadly threatened in Uganda.
“Like now when you go to where you used to find frogs they are almost non-existent because they have nowhere to breed, they do not have anywhere to hibernate,” Musingwire said.
For the Ugandan herpetologists, the hope is that the results of the completed survey later this year will include a sighting of a rare frog in the torrents on the slopes of Mount Elgon. Regardless, the team’s work will give Uganda’s environmental officers and conservationists a clearer picture of the presence of amphibians in this part of the country, and how to better protect their habitat.
Banner image: Detail of a photo of a Natal dwarf puddle frog in the Gambia. Image by Thomas Brown via Flickr (CC BY-NC-SA-2.0)
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