The largest known cave roost of bats in the Pacific region has been discovered on the island of Vanua Balavu on the remote Lau archipelago in Fiji.

Significantly, this roost houses a considerable population of the endangered ‘Pacific Sheath-tailed bat’ (subspecies Emballonura semicaudata semicaudata), marking a key moment in the efforts to conserve this endangered species.

A conservative estimate places the number of bats in the newly discovered cave at around 2,000 to 3,000. This important find was made possible by a rapid assessment mission led by Conservation International in Fiji in April 2023. The mission was a joint effort with the Australian Museum and the University of Adelaide, aimed at cataloguing and studying the diverse species in Lau. 

The bat-related initiative of the mission was spearheaded by world-renowned mammal expert, Professor Kristofer Helgen, Chief Scientist and Director of the Australian Museum Research Institute.

“We have found what we now believe is the biggest population and roost for this species in Fiji and the region. The size of the roost found, numbering in thousands, gives us a remarkable insight into the potential population size and distribution of the bats, which may be larger and more spread out than previously thought,” said Professor Helgen.  

For comparison, the most recent previous assessment for this species, published in 2019 by the International Union for the Conservation of Nature, noted that there were approximately 2,000 bats in Taveuni, Fiji recorded in 2018—a figure that had unfortunately declined to only a couple of hundred bats by 2019. This positions the Lau archipelago discovery as the most significant concentration of this subspecies in the Pacific to date.  

“It is noteworthy to mention that several other smaller caves on the same island have been identified as housing this endangered species, providing new hope and further amplifying the island’s significance in conservation efforts of this species,” said Helgen.

Conservation International Senior Director Fiji Programme and Regional Fisheries Mere Lakeba said the unexpected discovery in northern Lau has shifted renewed conservation focus onto the Pacific Sheath-tailed bat, adding that “the finding has significant importance for CI’s Lau Seascape Strategy.”

“This finding is a landmark in the context of Conservation International’s Lau Seascape Strategy. It serves as a powerful catalyst that energizes our terrestrial conservation strategies and reinforces our unwavering commitment to safeguard and restore the distinct biodiversity of this irreplaceable ecosystem.”

“It sends out a strong message that persistent research, exploration, and conservation efforts are essential to discover the presence of endangered species such as this, hidden in our biodiversity. It’s these relentless pursuits that enable us to redefine and enhance our strategies for preservation,” said Lakeba.

Lakeba also acknowledged the indispensable role of the Indigenous community of Lau, describing them as “more than just custodians of the land. Their profound understanding of the land, shaped by generations of traditional practices and wisdom, will be instrumental in safeguarding the newly discovered subspecies of the Pacific Sheath-tailed bat population and their roost in the Lau Seascape.”

Further heightening the importance of this discovery is the fact that the Pacific Sheath-tailed bat population has seen a rapid global decline. In the Pacific, this specific bat subspecies, Emballonura semicaudata semicaudata, is extirpated from countries where it used to live, like Tonga, Samoa, American Samoa, and Vanuatu. In Fiji, this subspecies has been lost from a significant conservation roost in Yaqeta, Yasawa, a place where it once existed in hundreds.

Professor Helgen stressed that “the virtual extinction from other regions of the Pacific makes this new roost in Fiji a monumental find and the most important stronghold for the species’ conservation in the region.” 

“Pacific Sheath-tailed bats are ecosystem superheroes. They are nature’s pest controllers, and biodiversity barometers, helping maintain ecological balance. Their existence provides invaluable insights into environmental health and important focus for further scientific research in the Lau Group of Fiji. In essence, their survival is not just about them, but the health, prosperity, and balance of the world we share,” explained Professor Helgen.  

University of Adelaide Associate Professor, Dr Wayne Boardman, who was part of the mission described the discovery as a “career highlight.” 

“While this is the biggest population of the species in the Pacific which has been discovered to date, it is still not enough to remove the species from the endangered list,” said Dr Boardman. “It just gives us more hope that the population is in a slightly healthier position than it was before and all the more important to protect it.”

Siteri Tikoca, a Fijian researcher at the University who was also part of the mission added: “Discoveries this striking for an endangered species are rare and present a more accurate foundation for conservation planning; they provide researchers with valuable information about this habitat, behavior, and population size. It is not just about recording an existence – but we must take steps to protect this site and this species before it is too late.”

The Pacific Sheath-tailed bat is listed as Endangered under the International Union for Conservation of Nature (IUCN) Red List of Threatened Species due to declining rates in the Pacific Islands and is listed as one of the 35 species on Bat Conservation International’s worldwide priority list for conservation.

This story was written by Priya Chand, originally published at Conservation International on 29 August 2023.