Guided by native villagers, the bat biologists descended into the mouth of a cave on Fiji’s distant island of Vanua Balavu. They slipped down a rock face, swam by means of an underground pool, clambered over piles of guano and emerged right into a cathedral-sized cavern “completely chockablock-full” of Pacific sheath-tailed bats, says Kris Helgen, a mammal knowledgeable and chief scientist on the Australian Museum Analysis Institute in Sydney.

Hundreds of the animals stuffed the cave like a cloud, and Helgen might really feel the whoosh of their delicate wings as they zoomed round him at midnight. “It was a panoramic second,” he says.

The April expedition, led by the nonprofit group Conservation Worldwide, had not solely found the most important identified bat cave within the Pacific Islands, with a inhabitants conservatively estimated at 2,000 to three,000; the researchers had additionally discovered new hope for a creature they’d feared was racing towards extinction.

Pacific sheath-tailed bats have tender, chocolate-brown fur and attain simply 5 grams—the load of a nickel or a sheet of paper. Just a few million years earlier than people sailed throughout the Pacific and made their properties on island after island, these tiny bats undertook the identical astonishing journeys—by air. (A associated species, the marginally bigger Brazilian free-tailed bat, can fly 160 kilometers in a single night time.)

The Pacific Islands have 191 identified bat species, from tiny insectivorous microbats such because the four-centimeter-long sheath-tailed bats to fruit-eating flying foxes that dangle in timber and have a wingspan of a meter. Folks within the area acquire bats’ guano for fertilizer, hunt them for meals and—within the Solomon Islands—even use their enamel as conventional forex.

Sheath-tailed bats had been as soon as among the many Pacific’s most widespread mammals however at the moment are one in every of its most threatened. Lower than a century in the past they had been discovered throughout Oceania, from Guam to American Samoa. In the present day the 4 acknowledged subspecies at the moment are thought to outlive on only a few Micronesian and Fijian islands.

The archipelagic nation of Fiji is the “final stronghold” of the sheath-tailed subspecies Emballonura semicaudata semicaudata, says expedition member Siteri Tikoca, a Fijian conservation biologist and a Ph.D. candidate on the College of Adelaide in Australia. However in Fiji, too, the bat’s populations have been plummeting.

Some necessary roosts at the moment are utterly devoid of bats. Tikoca says she counted round 1,000 sheath-tailed bats in 2018 in a cave on the island of Taveuni, roughly 120 km northwest of Vanua Balavu. By 2019, the forests had been cleared nearly to the mouth of that cave—and only a few hundred bats remained.

Tikoca says discovering such a wholesome roost within the Vanua Balavu cave was a “lovely” second that rekindled her hope for these bats. However the Taveuni state of affairs “emphasizes the necessity to defend them now as a result of a lot can occur inside a span of 1 12 months,” she says. “If we do not do something for it in Fiji, then we are going to lose this subspecies fully.”

Conservation Worldwide says it’ll now work with the world’s Indigenous communities to raised safeguard the cave. “We’re all of the richer for the truth that they’ve taken care of these landscapes, these caves and finally these bats,” Helgen says.

The insectivorous bats are thought to play a key function within the surrounding ecosystems, consuming crop pests and controlling disease-bearing mosquitoes. Studying extra about these creatures’ ecology is crucial, Tikoca says, and is a vital first step towards doubtlessly relocating sheath-tailed bats to a few of their former haunts.

“That is such a formidable discover and a large win for the species,” says Jon Flanders of Bat Conservation Worldwide, who was not concerned within the expedition. Worldwide, 270 new bat species have been described since 2005, he says—and this newest discovery suggests different Pacific islands might shelter but extra winged surprises. “It simply goes to point out how little we nonetheless learn about bats,” he says.