In January, 2019, a multinational team of biologists set out into the rain forest of southwestern Rwanda, in search of a near-mythical bat that they thought might be extinct. The Hills’ horseshoe bat—agacurama in Kinyarwanda—hadn’t been seen in forty years. Scientists had caught and recorded it only twice, in 1964 and 1981, roughly five miles apart, in a forest reserve named Nyungwe. But then conflict and war, culminating with the genocide in 1994, devastated the region. Many of Nyungwe’s research and tourist facilities were destroyed. Subsistence agriculture, sometimes undertaken by people fleeing conflict, along with things such as logging and mining, caused the forests surrounding Nyungwe to largely disappear.
Paul Webala, a Kenyan wildlife biologist and one of the expedition members, had started work in 2013 on a monograph of the bats of Rwanda. “Not much was known,” he told me. “Records were old” and lacked echolocation data. The Hills’ horseshoe bat was the only Rwandan bat species, out of fifty-four found in the country, which the International Union for Conservation of Nature (I.U.C.N.) had listed as critically endangered. Webala wondered whether it was lost simply because no one had gone looking for it. He recruited the help of Julius Nziza, a Rwandan wildlife veterinarian for Gorilla Doctors, to conduct reconnaissance surveys. By then, the government had made Nyungwe Forest a national park; its four hundred square miles had become the largest protected tract of Afromontane rain forest in the Albertine Rift, a hotspot of endemism that stretches from Uganda to Zambia. Many of its animals and plants are found nowhere else on Earth. After more than a year of searching, however, Webala and Nziza started to think that the Hills’ horseshoe bat was found nowhere on Earth. During the course of two expeditions, they surveyed ten sites and found eight other bat species, but not Hills’. Was it extinct?
A million species currently face extinction, “many within decades,” a landmark biodiversity report, authored by more than three hundred scientists, reported in 2019. The rate of plant and animal extinction is already as much as hundreds of times higher than it has averaged over the past ten million years, and is expected to accelerate. At the same time, “biological communities are becoming more similar to each other,” the report’s summary said, leading “to losses of local biodiversity, including endemic species, ecosystem functions and nature’s contributions to people.” Nature, in its increasing homogeneity, is going the way of the American fast-food chain.
To address the catastrophe, delegates from the world’s nations recently met in Geneva to renegotiate the Convention on Biological Diversity, an international treaty first enacted in 1993. Progress was notable on the “30x30” initiative—to protect thirty per cent of Earth’s land and seas by 2030—which scientific consensus indicates is the absolute minimum needed to help curb global biodiversity loss. A majority of participating countries announced their commitment to the goal. “There has never been this much support for this level of conservation in history,” Brian O’Donnell, the director of the Campaign for Nature, told me. But countries will still need to formally adopt the global target—and a new, binding biodiversity framework—at the fifteenth Conference of the Parties, or COP15, now anticipated to start in August, in China. For leaders from the developing world, which will be disproportionately responsible for conserving biodiversity, appropriately ambitious financing commitments from donor countries remain in question. “That will be the biggest obstacle to achieving an ambitious global agreement,” O’Donnell said.
Lost-species quests can seem like wild-goose chases, but as Barney Long, the senior director for conservation strategies at the nonprofit organization Re:wild, told me, you can’t save what you don’t know is there. “Unless we know the distribution of, and threats to, a species, we can’t put in place conservation actions to save it from extinction and put it on the road to recovery.” In 2017, Re:wild, under Long’s direction, created a list of its “Top 25 Most Wanted Lost Species.” Nearly all of them are now being sought by individuals or local organizations. The list reads like speculative fiction: the Ilin Island cloudrunner, in the Philippines; the Namdapha flying squirrel, in India; the Blanco blind salamander, in Texas. And, in many cases, the biological record is spotty at best. The only specimen ever collected of Fagilde’s trapdoor spider, in Portugal, for example, was lost in a museum fire in the nineteen-thirties. There are no known photos. The only illustration is a drawing of the female’s genitalia. But people continue searching.
“Lost species hold a particular fascination, rather like ships lost at sea,” the ecologist Deborah Rabinowitz wrote in a seminal 1981 article titled “Seven Forms of Rarity.” The Hills’ horseshoe bat, based on her scheme, was at the endemic extreme: a tiny population, geographically restricted to a specific habitat, then not seen by scientists for decades. And yet, these days, the kind of rarity the bat represents is common. “There are many different reasons why a species can become lost,” Long said. “Some are naturally rare, others are very cryptic or hard to find. Others are just in remote or hard-to-get-to places due to social conflicts or geography. Others were common, but due to a threat have been reduced to small numbers.”
Re:wild and the I.U.C.N.’s Species Survival Commission currently know of more than two thousand lost species, not scientifically documented in the wild for more than ten years, with no individuals under human care. Searches often begin with discussions with local and indigenous people. But the forces that are leading to biodiversity loss “also relate to the loss of indigenous and local knowledge about species,” Pamela McElwee, a human-ecology professor at Rutgers University, said. Over the past five years, conservationists around the world have notified Re:wild about sixty-seven rediscovered species. From Re:wild’s “Most Wanted” list, searchers have found eight, including the silver-backed chevrotain (a fanged deer-like creature the size of a rabbit) in Vietnam, the Somali sengi (a tiny, monogamous elephant shrew) in Djibouti, and the Fernandina Galápagos tortoise. “A rediscovered species is not one that is not in danger of extinction,” Diogo Veríssimo, a conservation research fellow at Oxford and a co-founder of the Lost and Found project, said. “But they do represent a chance to correct past mistakes in a kind of do-over.”
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The obsessive people who search for these animals are their own variety of rare—sparsely found across a wide geographic range, in all sorts of habitats. In New Zealand, an entire charitable trust is dedicated to finding and saving the South Island kōkako, a bird also known as the grey ghost, largely by mapping reports from people who have heard the bird’s haunting melodic call. “I know the bloody thing’s there, it’s just the mind-wrenching psychological difficulty of it all,” one kōkako chaser, Rhys Buckingham, said. In 1997, an English shopkeeper named Richard Thorns quit his job to search for the pink-headed duck in Myanmar. He’ll be leading another expedition later this year. “Finding that passionate individual or local organization that is inspired to focus on a lost species is what provides me with hope,” Long said. “When a species has its guardian trying to find it and save it, the odds of that species recovering increase exponentially.”
In Rwanda, on the hunt for the Hills’ horseshoe bat, Webala and Nziza became slightly obsessed, too. They decided to recruit help from scientists with Bat Conservation International (B.C.I.), an organization dedicated to ending bat extinctions worldwide. B.C.I. was eager to help. “Our thought at the time was, simply, Have we done enough surveys to reasonably conclude that Hills’ may indeed be presumed extinct?” Winifred Frick, B.C.I.’s chief scientist and a member of the expedition, told me. If so, funds could be directed elsewhere. After several years of planning, fund-raising, and reconnaissance, Frick and her colleague Jon Flanders, B.C.I.’s director for endangered-species interventions, travelled to Rwanda—carrying ski bags full of nets, traps, and ultrasonic audio equipment—to join Webala, Nziza, and other Rwandan conservationists on the quest.
Every day they hiked the forest’s old trails, often in pouring rain. (It was supposed to be the dry season.) Thirteen species of monkeys and apes, including chimpanzees, filled the forest canopy. Rwandan park managers had helped identify ten caves, an abandoned mine, and a building as likely roosts. “The caves were all super-shallow, super-tight, kind of muddy,” Frick said. “Like you were on your belly, pushing off the ground with your toes, shoving yourself deeper into this hole in the ground that nobody had ever been in before.” She added, laughing, “I had some panic attacks.” They found signs of bats: cave-wall stains, guano piles. But they did not find Hills’ horseshoe bats.
The team was unable to camp in the park, so they only had a few hours in the evening to work. At dusk, they set up mist nets to capture bats. But torrential rains made the work nearly impossible, and they often had to close the nets early. They could, however, leave up harp traps all night. Bats fly into the traps’ nylon strings, which are vertically fastened between two rods—like a rectangular harp—then they slide, fall, or shimmy into a canvas bag hanging below. “We had to rush back to them before dawn so we could check the trap, remove any bats, measure them, and ultimately release them before daylight,” Frick said. “They don’t feed in the light, and the sun could be stressful and make them more vulnerable to predators.”
A few days into the expedition, at 4 A.M., the researchers drove the hour and a half from where they were staying, outside the park, to Uwinka, a watershed within Nyungwe where the original two Hills’ horseshoe bats had been found. At the harp trap, they started pulling bats from the bag, and, as Frick later whispered to me, “We found treasure.” The small, plump, furry bat that Webala pulled out looked sort of like other horseshoe bats, Frick said, but “the facial features were exaggerated to the point of comical.” The bat’s face was alien, an evolutionary screwball fit for the dark, featuring tiny button eyes, an inflated horseshoe-shaped snout, and, for a nose, a vulval sculpture of rippled and jutting skin flaps. Each pyramidal ear was striped, and larger than the bat’s face. “We were definitely really excited,” Frick said, “but also kind of doubtful. It almost seemed too easy.”
They took measurements, photographs, and a wing punch (a millimetre-wide sample of tissue—i.e., DNA—from the wing, which heals within a few weeks). Frick then released the bat, and Flanders ran after it, holding a special ultrasonic microphone connected to a laptop, in order to record its release call. As it turned out, the bat had a strange, distinctive echolocation call, which it emitted at a consistent frequency, much lower than that of other horseshoe bats. “It’s very handy for us,” Frick said. By distinguishing Hills’ from other bats, it allows for easy acoustic surveillance. They might not see the bat, but they can detect it flying.
Back at their camp, they pored over the literature on Hills’ horseshoe bats, to confirm that their measurements matched. “We weren’t going to call it right there, right then. We were going to do our due diligence,” Frick said. “But we were pretty sure.” One evening, they recorded an echolocation call that matched the Hills’ recording. “We were in the heart of some deep forest without any known caves nearby,” Frick said. It was too soon after sundown for the bat to have flown far. “So we think this species might roost in big old trees,” Frick said. As the week passed, the rains grew more intense, they couldn’t find any roosts, and the accumulated sleep deprivation started to fray nerves. “It just seemed like it got harder and harder,” Frick said. “So when it was the last night, it was almost to the point of, like, should we even try again?” Nevertheless, they set their mist net. Just before dawn, one more bat hit the mesh, its wings quietly tangling. There were hollers; it was another Hills’ horseshoe bat. “It was a eureka moment for us,” Webala said. They passed around a bottle of Rwandan whiskey.
“There was such an element of surprise and disbelief,” Frick said. “This elusive creature has been flying for forty years, unknown to humans, living this secret life. And it’s amazing and special and precious that we have the opportunity to say, ‘O.K., you’re still here.’ Then we let it go, let it fly back out into the forest.”
