by Shaena Montanari
It had been nearly four decades since anyone had observed a Hill’s Horseshoe Bat (Rhinolophus hilli) in the montane forests of Rwanda. The bat, which is listed as Critically Endangered by the International Union for Conservation of Nature (IUCN), is enigmatic, known only from two individuals caught in Nyungwe National Park, most recently in 1981.
Now, Bat Conservation International (BCI) and the Rwanda Wildlife Conservation Association have announced that Hill’s Horseshoe Bat has been rediscovered inside the park, which the researchers hope will lead to new information about this mysterious, at-risk species.
Dr. Jon Flanders, the Director of BCI’s Endangered Species Intervention Program, says a two-week field expedition to Rwanda in 2019 revealed this species is still present in the park, albeit rare and very difficult to find.
The only place Hill’s Horseshoe Bat has ever been found is in Nyungwe National Park, a protected rainforest just over 380 square miles in size and home to endemic wildlife, including 12 primate species, as well as rough terrain and towering waterfalls. This bat and other wildlife in the park have been impacted by decades of deforestation and human encroachment in the country.
BCI began collaborating with rangers at the national park and researchers from Rwanda, Kenya, and the Democratic Republic of the Congo in 2016 when Dr. Winifred Frick, Bat Conservation International’s Chief Scientist, traveled to Rwanda.
Dr. Frick says that when Dr. Paul Webala, a researcher and senior lecturer at Maasai Mara University in Kenya, thought he may have found a Hill’s Horseshoe Bat, it led to the “tantalizing thought” that this bat may still be extant. In the following years, Dr. Frick and other researchers soon solidified a multinational collaboration that led to the 2019 expedition.
During the expedition, researchers identified two bats they suspected could be Hill’s Horseshoe Bats, and were able to obtain measurements, photographs, and DNA samples from the bats. Confirming they had found Hill’s Horseshoe Bat wasn’t instantaneous. Dr. Flanders and another colleague had to examine two existing museum specimens in Belgium and Switzerland to definitively say they did catch two Hill’s Horseshoe Bats in 2019.
Thanks to a partnership with Wildlife Acoustics, researchers and rangers were able to collect echolocation data from this species using acoustic detectors for the first time ever during the field expedition. Being able to identify the species from their echolocation signatures allows the researchers to set out acoustic bat detectors and determine where the bats are foraging and commuting in the forest.
“Placing acoustic detectors in the forest is an efficient way to eavesdrop on the bats without them even knowing we’re checking in on them,” Dr. Frick says.
There are multiple species of horseshoe bats that live inside Nyungwe National Park, so this new acoustic information can help tell them apart. Even after the two-week expedition ended, park rangers were able to spend the next nine months deploying acoustic recorders to 23 locations in the park to collect additional data and continue to listen in on the bats.
Though the team of researchers learned a lot about the Hill’s Horseshoe Bat, much about the species remains unknown. One thing they still don’t know is where exactly these bats roost in the rainforest. While they previously thought the bats may be roosting in caves, since many species of horseshoe bats do, Dr. Frick says this species has not been observed in or near a cave. “To the best of our knowledge at this point, it may seem much more likely that the species could actually be tree roosting, which would be very interesting.”
The bat’s specific diet, too, is still a mystery. Because researchers caught the two individuals early in the evening with empty stomachs, “we have no idea what insects they’re eating,” says Dr. Flanders.
Researchers hope to head back to Rwanda this year to see if a second expedition will turn up more Hill’s Horseshoe Bats. Dr. Frick says they would also like to expand the search for the species in other forested areas in the region.
“The idea is to continue to expand our knowledge about where the remaining populations may be located,” Dr. Frick says.