- For the first time in 40 years, researchers caught a Hill’s horseshoe bat, confirming that the bat population still clings to life in Rwanda’s Nyungwe National Park, a highly biodiverse area containing old-growth cloud forest.
- Rhinolophus bats echolocate through the unique and exaggerated folds on their noses called “nose leaves,” which, in the case of the Hill’s horseshow bat, gives them a bass frequency, unlike the soprano of other horseshoe bats.
- Now that researchers have identified their call, they can use acoustic monitoring to eavesdrop on the critically endangered species with minimal impact.
- A lead researcher on the team said the bats are likely restricted to a core area, and although the park is well-patrolled by rangers, this area should be a focus in order to protect the remaining bats, whose population remains unknown.
“When we caught it, we all just looked at it and said, ‘You look ridiculous. Look how big your nose leaf is,’” Jon Flanders, director of endangered species interventions at Bat Conservation International, told Mongabay. The odd-looking creature in their net was a Hill’s horseshoe bat (Rhinolophus hilli)—the first seen since 1981.
“We feared the species may have already gone extinct,” Flanders said. “To think that we’ve been the first people to actually see this bat in almost 40 years … It was just remarkable.”
Flanders was part of a 10-day, 10-night expedition searching for the elusive bat in the old-growth cloud forests of Rwanda’s Nyungwe National Park. The fieldwork was brutal, he said, almost continuous rain pummeling down as they hiked through the steep terrain on little sleep. But their work paid off one night around 4 a.m. when they pulled the odd-looking bat from their net.
“We knew immediately that the bat we had captured was unusual and remarkable,” Winifred Frick, chief scientist of Bat Conservation International and a member of the expedition, said in a press release. “The facial features were exaggerated to the point of comical.”
As soon as they caught the fluffy, wrinkle-faced mammal, Flanders said, the group went nearly silent and began poring over textbooks to be sure of their find.
On their quest for the lost bat, the researchers used a series of traps, including a very fine net known as a mist net that is used to catch birds and bats. When mist-netting, researchers try to release their catch as quickly as possible to minimize stress to the animal, especially when that animal is critically endangered.
So, Frick made measurements while Flanders recorded the bat’s echolocation calls and others compared notes in their bat books. “We just know that the clock is ticking before we have to let the thing go,” Flanders said.
Frick was able to capture the first recording of the Hill’s horseshoe bat. But initially, he didn’t trust the readings, which registered the call at an unusually low frequency. Once they let the bat go, it flew along a nearby road and Flanders said he sprinted after it in the moonlight with his recorder, confirming that, while other species of Rhinolophus bats are sopranos, the Hill’s horseshoe bat is a bass.
“Their nose is just phenomenally shaped and they echolocate through their nose, which is part of the reason why they have this really unique and exaggerated nose leaves … so they can control the call partly through their nose folds,” Flanders said. “No bats in the U.S. echolocate through their nose. It’s really an Old World trait.”
Knowledge of the bats’ calls comes in handy as a low-impact conservation tool. Now, rangers and researchers can survey for bats using sound detectors alone, “which is great,” Flanders said, “because we have a critically endangered bat of unknown population size … this way it’s zero impact because we’re just eavesdropping on them as they’re flying around and doing their normal behaviors.”
“Knowing the echolocation calls for this species is a game changer,” Paul Webala, senior lecturer at Maasai Mara University in Kenya and one of the team’s lead scientists, said in a press release.
Flanders said the project couldn’t have been done without the Nyungwe park rangers, who found most of the caves and mist-net locations before the researchers arrived and have now recorded more than a quarter of a million audio files to survey for bat calls. He also credits the collaboration between Bat Conservation International, the Rwanda Development Board and the Rwanda Wildlife Conservation Association.
The collaborators have plans for another expedition this year to further study the bats’ behavior, DNA sequence their guano (droppings) to figure out what kinds of insects they eat, and find where the species roosts (none have been found roosting in caves like their other Rhinolophus relatives). While other bats like to hide in small crevices, these hang out in the open with their wings wrapped around their fluffy bodies, “looking a bit like a ripe plum,” Flanders said.
“Now our real work begins to figure out how to protect this species long into the future,” he said.
So far, acoustic monitoring suggests that the bats are restricted to a small core range in the park. Flanders said the forest is well patrolled by rangers, but that staff should “double down” on this core area where the critically endangered bat lives to make sure no one is damaging this critical habitat.
Significant amounts of Nyungwe National Park have been lost or degraded through poaching, fires and agricultural encroachment, and although the Rwandan government has made significant investments in protecting the park and halting this destruction over the past decade, Flanders said, there are still threats.
“Nyungwe National Park is one of the most biologically important montane rainforests in Central Africa, supporting an exceptional range of biodiversity including many rare and endemic species, including bats,” said Eugene Mutangana, conservation management expert for the Rwanda Development Board.
In another study that took place in the park, researchers placed 108 cameras in trees. In one month, they spotted 35 different mammals, including six primate species.
“A lot of people think that by now we know everything … but we just found a new species here,” Jennifer Moore, lead author of the camera trap study and a researcher at the University of Florida, told Mongabay in a 2020 interview.
“So that just goes to show that even in places where researchers have been for decades, there is so much more to learn.”
Banner Image of Hill’s horshoe bat by Jon Flanders, Bat Conservation International
Liz Kimbrough is a staff writer for Mongabay. Find her on Twitter @lizkimbrough_
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