1,500 Bat Species and Counting

he moment Rohit Chakravarty, Ph.D., saw the bat in the mountains of India’s Uttarakhand state, he knew it was the one he had been seeking for four years. He’d last spotted the species years before, and Chakravarty was eager to examine what would soon be named the Himalayan long-tailed bat (Myotis himalaicus). Chakravarty is Bat Conservation International’s (BCI’s) India Program Manager, and he joined taxonomist Uttam Saikia, Ph.D., and the rest of their team in the field that day to examine the bat they’d carefully netted, evaluating its measurements and the shape of its head and teeth.

“Our team was able to work out a suite of external, cranio-dental (head and teeth) and bacular (penis bone) characteristics unique to this species,” Saikia says. “Supported by genetic data, we were able to confirm that it indeed belongs to a new species.”

Identifying bats is a challenge for scientists, who often use multiple methodologies, including charting each bat’s physical characteristics and analyzing its genomic information, to discover if it is truly a species not yet described by science. Comparing samples to museum specimens of previously recognized species is also a key way to determine if a species is new to science. More than 1,500 unique bat species are known to science, though the number continues to increase each year as more species are described.

Identifying distinct bat species is important for many reasons, including conservation.

“Recognizing different species, especially cryptic species, continues to be vitally important for conservation efforts by defining the scale of diversity we need to protect,” says BCI Chief Scientist Winifred Frick, Ph.D. BCI tracks the latest information on bat species diversity in order to ensure bat conservation efforts are targeted to benefit bat diversity.

The methods the team used to identify the Himalayan long-tailed bat were a combination of traditional and more modern bat identification techniques that perfectly illustrate scientists’ ability to tease out the subtle identifiers that distinguish a bat species.

“The best case is where the bat looks different, behaves differently, and has a different genome,” says Nancy Simmons, Ph.D., Curator at the American Museum of Natural History and BCI Board Member.

That’s why identifying a bat is an impressive and ever-evolving science that utilizes multiple methods.

Simmons, who runs the database of known bat species called batnames.org, knows firsthand how critical these choices can be. She formed the Global Bat Taxonomy Working Group, a formal committee of the IUCN Bat Specialist group, to help grapple with decisions regarding which new discoveries should make it into the database. The group considers newly published bat research to determine if the data and methods are sound enough to justify the claims being made.

“In some cases, it takes a lot of discussion,” she says. “We go back and reread a bunch of papers, and eventually we come to, ‘Alright, this is our best guess.’”

Historically, most bats were identified by external morphological traits, including the distinctive physical characteristics that Chakravarty, Saikia, and their team, including Manuel Ruedi, Ph.D., and Gabor Csorba, Ph.D., found during their examination of the Himalayan long-tailed bat’s head, teeth, and pelvis.

These morphological traits also helped the team figure out that an unidentified specimen that had been caught by Gábor Csorba, Ph.D., in 1998 was also a Himalayan long-tailed bat.

However, identifying bats just by physical characteristics can be a challenge. “We’ve come to learn that there’s a lot of cryptic species diversity if we just look at the external morphological traits of bats,” Frick says. “By using modern genomic and genetic tools, we can see the species divergence in the genomes of bats, and that’s provided a much fuller picture of the level of diversity that we have.”

This fuller picture also helped BCI discover Nimba myotis (Myotis nimbaensis) in 2021. The little orange bat, discovered in Guinea’s Nimba Mountain, was captured during surveys of old mining tunnels.

“When I first started working with bats, the only way you could build a family tree of a set of organisms was using morphology, so anatomical traits,” Simmons says. Today, genomic methods that classify bats by analyzing their DNA are getting more sophisticated every day. “You can use a single gene to figure out where an animal goes amongst close relatives,” Simmons says. “Or you can use the entire genome, which is the direction we’re moving in now.”

Genetic analyses of different kinds can also reduce the number of bats that need to be captured for research purposes. Scientists have recently discovered that environmental DNA (eDNA) naturally shed by bats can be used to study their habits and migration patterns. For example, bat species visiting hummingbird feeders can be detected by swabbing the feeder the next day. Of course, scientists can’t build a genetic database to compare samples to without catching bats. But while capturing and keeping the whole bat used to be standard, today’s methods often make it possible to gain plenty of information by collecting a small tissue sample and other methods.