• Rwanda is home to 51 known bat species, and many of them live in Nyungwe National Park. However, habitat loss and fragmentation, mining, logging, hunting, burning, and other activities threaten bats and other species.

Photo: Dr. Winifred Frick

Dr. Jon Flanders’s feet pounded as he raced as fast as he could down  the muddy road. Kicking up chunks of mud that splattered all over his legs, Dr. Flanders, Director of Endangered Species Interventions for Bat Conservation International, held an acoustic bat detector in the air with one arm as he ran, hoping to catch as many fleeting sounds as possible. If the preliminary data meant what the scientists thought it did, the bat flying down the road—which he was racing after—was an incredible find. It was one that hadn’t been spotted in nearly 40 years: the Critically Endangered Hill’s Horseshoe Bat (Rhinolophus hilli).

It was January 2019, at the tail end of the dry season in Rwanda’s Nyungwe National Park, but the rain was relentless. Dr. Flanders was one of 10 scientists and researchers from Rwanda, Kenya, the Democratic Republic of Congo, and the U.S. who came together in the field for 10 days to study the park’s bats and search for the elusive Hill’s Horseshoe Bat.

At times, the scientists would huddle under a tarp strung up between two vehicles in a futile attempt to stay dry while working on sample collection. The team worked late into the night, then drove out of the park to catch a few hours’ sleep before getting up at 3 or 4 a.m. to try and catch bats to measure them and collect samples for DNA analysis before the sun rose. Their lodgings were located some distance away, and park rules did not permit them to stay in the park overnight.

Despite the weather and challenges, the team’s accomplishments were remarkable. In addition to ultimately confirming the presence of Hill’s Horseshoe Bat—a time-consuming process that involved intercontinental legwork—the trip also yielded another amazing find: the first record of the Damara woolly bat (Kerivoula argentata) in Rwanda. Additionally, it was the first time Lander’s horseshoe bat (Rhinolophus landeri) was recorded in Nyungwe National Park.

“The whole survey was really, really beneficial,” says Dr. Olivier Nsengimana, Founder and Executive Director of the Rwanda Wildlife Conservation Association, and one of the project’s key collaborators.

Fifty-one bat species are known in Rwanda, many of them in Nyungwe’s nearly 400 square miles of rainforest. However, threats like habitat loss and fragmentation, mining, logging, hunting, burning, and other concerns threaten bats and other species.

The team captured two individuals they believed were Hill’s horseshoe bats in the field, but they weren’t able to positively identify them until later. However, their data strongly suggested these bats were Hill’s horseshoe bats: the nose leaf was slightly different from other Rhinolophus bat species in the area, and  they had a very distinctive echolocation call compared with other local bats. The team was ultimately able to sequence DNA from the bats they caught in Rwanda, providing the certainty they were looking for. “Without a doubt, it was a Hill’s horseshoe that we caught,” Dr. Flanders says.

Park rangers conduct ongoing acoustic monitoring

Nyungwe National Park rangers have long played a key part in this research project, even before the international team traveled to the park to conduct fieldwork.

“Initially before this field survey, we had to engage the rangers in the forest to try and identify all the caves,” says Dr. Nsengimana. “It was really helpful that the rangers sent the GPS coordinates of places we think we can find the caves in the forest—it helped with planning.”

Photo: Dr. Winifred Frick

When the researchers were in Rwanda, they worked closely with park rangers, hosting an acoustic monitoring workshop to enable them to conduct acoustic surveys with bat detectors and transmit the data they collected. Acoustic analysis is also useful because it reveals areas where bats are not detected.

“We trained and empowered the rangers to be able to acoustically monitor areas in order to potentially identify areas where these bats are foraging, and potentially also roosting in,” says Dr. Paul Webala, Senior Lecturer at Maasai Mara University.

From July 2019 to March 2020, the park staff and rangers collected 119 nights of acoustic data from 23 locations within the park. Typically, they would leave one recording device at a site for four or five nights. Once they collected the data, they would email the files to Bat Conservation International for analysis. During this time period, Rwandan partners shared 262,896 files of bat calls—and they are still sending data. 

In eight locations, they detected the distinctive call of a Hill’s horseshoe bat. While the researchers were thrilled to detect them, they only found them within a small range, demonstrating how extremely vulnerable they are.  

It also shows what a challenge it is to find them, despite all the tools and skilled scientists working on the project. “It’s a large park, so it’s a ‘needle in a haystack’ sort of thing,” Dr. Flanders says.

Future projects in the works

The team hopes to return to Rwanda in the summer of 2022 to conduct further research, including catching Hill’s horseshoe bats and applying temporary radio tags to track their movements and learn more about where they roost. When they were examining the specimens they caught in 2019, the researchers noticed many similarities between the Hill’s horseshoe bat and a tree-roosting species in the Philippines. By tracking the bats, they hope to learn if the Rwandan bats roost in caves or in trees—where they would be even more vulnerable to habitat disturbance, such as logging, fires, or trees naturally falling.

Hill’s horseshoe bat. Dr. Winifred Frick

Dr. Webala points out the importance of learning more about the species and its life history in order to conserve them. “It’s very important to have this information, a picture of where they’re roosting, for the conservation of the species that is endangered,” he says.

They also hope to collect fecal samples and learn more about their genetics and diet. The two bats they caught previously were just leaving their roosts so they hadn’t eaten yet, making sample collection impossible.

Dr. Flanders, Dr. Nsengimana, and Dr. Webala all agree the highly collaborative nature of the 2019 expedition led to its success. “Working together is the key,” Dr. Nsengimana says. “It was kind of a huge operation that brought together so many bat experts.”