As evening fell on Barro Colorado Island (BCI), Maryna Yerofeieva put her headlamp around her neck, laced up her combat boots, and headed into the forest. As she followed the trail downwards into a ravine, she fell in line with the researchers ahead of her, carefully stepping from cinder block to cinder block. She had flown halfway around the world for what she was on her way to do: catch Neotropical bats.

Maryna had traveled to Panama from Kharkiv, a city less than 20 miles from Ukraine’s Russian border, through the Human Frontiers in Science Program (HFSP) Organization’s “Scientists for Scientists” relief grant for Ukrainian researchers affected by the Russian invasion to join active HFSP research projects. In total, four researchers – all women – received funding to participate in the Panama-based project, two of whom were on Barro Colorado Island for this field season. The group was completing the first of several surveys for a three-year study investigating self-medication, the deliberate consumption of plants or minerals to relieve sickness and infection in animals.

Led by Rachel Page, a staff scientist at the Smithsonian Tropical Research Institute who has been studying Panama’s bats for more than two decades, the BCI team spent the half hour before sunset deploying a series of mist nets. These nets, which are so fine they resemble their namesake mist, are used to safely capture bats as they leave their roosts to begin the nightly hunt. After setting the nets, Kseniia Kravchenko – co-founder of the Ukrainian Bat Rehabilitation Center and fellow Scientists for Scientists grant recipient – walked several paces away to wait quietly with Maryna, eyes adjusting to the forest’s early darkness.

Common noctule bats (Nyctalus noctula) are migratory, insectivorous, and the most common bat species in Ukraine. In late summer, they live in the wooded areas outside Kharkiv to mate and feed on insects to sustain them for the long winter ahead. When winter comes, they return to the city with full bellies, looking for a place to hibernate until spring.

Inadvertently, humans have made cities into bat hibernation hotspots. “Our hypothesis is that modern cities, especially large buildings made of concrete, attract them,” said Kseniia. The number of bats in Kharkiv has greatly increased over the last 30 years due to increased urbanization and climate change which have altered the movement patterns of this migratory species. The imperfections in Kharkiv’s buildings, like cavities and crevices, mimic natural hibernation spots that bats would otherwise find in mountains or rocky landscapes.

As the number of bats has increased, so has the frequency of unwanted interactions between humans and bats. Seeing a need for a centralized organization to help keep both bats and humans safe, Kseiina and her colleagues Anton Vlaschenko and Alona Prylutska co-founded the Ukrainian Bat Rehabilitation Center twelve years ago. The Center – which is the largest of its kind in Eastern Europe – has supported bat rehabilitation, research, public outreach, education, and a bat rescue call center for over a decade. The operation is impressive and time intensive: each bat in artificial hibernation – and there are thousands – is woken up for individual feedings and check-ins until their springtime release.

The Center had their hands full rescuing bats from the everyday dangers of urban life before bombs began to fall on their city. Since Russia launched a full-scale invasion of Ukraine on February 24, 2022, Russian missile, rocket, and drone attacks have destroyed residential and governmental buildings alike, killing hundreds of Ukrainian citizens and forcing about half of Kharkiv’s population of 1.5 million to flee the city. The Center’s work has been impacted, too; the team had to evacuate their outdoor bat cage at a satellite facility because it was too close to the front line. Barabashovo Street Market, which is one of the largest markets in Eastern Europe and is located near their old office building (which they have since left for a bigger office space with more constant access to electricity and water, as well as an underground shelter space), was bombed. “We don’t know why – there is no military. There are many questions, and there is no why,” said Kseiina.

The destruction caused by the war has also affected Kharkiv’s bats. Usually, the Center has around 2-3,000 bats that it supports through the winter. This past year, 2023-2024, that number rose to 6,000. The Center rescued 2,000 bats from a single building at Karazin Kharkiv National University, where Maryna was studying at the time. Russian blasts damaged the frames of the building’s double paned windows, and when workers went to fix the broken windows, they found thousands of bats trapped inside. The animals’ finely tuned echolocation, which normally enables them to be acrobatic, deft flyers, boomeranged back and forth between the parallel windowpanes, offering no clues on how to escape.

— — —

Maryna’s headlamp scanned across the mist net, stopping on something fist-sized, furry, and wriggling: a fringe-lipped bat (Trachops cirrhosus). Within the family of leaf-nosed bats commonly found on BCI, this frog-eating bat eavesdrops on the tropic’s nightly amphibian chorus, picking off frogs as they call for mates. While bats in Europe mostly eat insects and the occasional bird, bats in the tropics have a diet that’s much more varied, including frogs, small rodents, insects, fish, birds, lizards, blood, fruit, nectar, and even other bats. Maryna recounted the first time she saw a frog-eating bat in Panama: “I saw the Trachops with a frog in its mouth, and I thought wow, this is not real!”

Tropical bats have displayed other interesting, and sometimes mysterious, dietary choices. Fruit-eating bats in the Amazon have been documented to attend mineral licks while pregnant or lactating, eating clay or drinking clay-enriched water. Fruit-eating bats will occasionally eat specific leaves, which have far fewer nutrients than their normal diet. The reason for these behaviors is unclear. One explanation could be self-medication, the consumption or use of therapeutic compounds in animals to alleviate sickness or infection. Although self-medication has been studied in many species, it hasn’t yet been documented in bats. Rachel Page, staff scientist at STRI, Ralph Simon, sensory ecologist at Nürnberg Zoo and Friedrich-Alexander Universität Erlangen-Nürnberg, and Daniel Becker, a disease ecologist at the University of Oklahoma, sought out to change this with the creation of the cross-disciplinary, cross-country SELFCURE project.

Their reasoning to investigate this behavior in bats is twofold. First, bats can harbor a wide variety of parasites and diseases, some of which may induce self-medication behavior. “We understand surprisingly little about how pathogens spread and circulate in bat populations,” said Daniel, adding that this limits our understanding of the trajectory of epidemics. Meanwhile, self-medication behavior has the potential to influence whether diseased bats recover, or if they get sick in the first place. “This is important both for monitoring bat health for conservation purposes, and for figuring out when and where to limit bat-human interactions to prevent pathogen spillovers.”

Second, bats have an excellent spatial memory and strong social bonds. Some species share information about suitable roosts and return to their historic feeding, hibernating, and pupping grounds year after year. Vampire bats, which are a highly social species, groom each other and share regurgitated bloodmeals if a member of their colony wasn’t able to feed that night. This behavior has been shown to change when vampire bats are sick; like humans, vampire bats will social distance from each other when they’re feeling sick, which may keep their illness from spreading to the rest of the colony. But there’s an exception: their closest relatives stick around to continue to care for them even when sick.

Considering their extraordinary cognitive abilities and dynamic social relationships, the SELFCURE team wondered if bats could learn to associate specific foods with curative properties – and communicate that information among their social networks. By 2026, Ralph hopes their suite of behavioral and immune-challenge experiments will show “where bats go when they’re sick, what foods they select in the wild, and if they can learn these behaviors by observing other bats.”

The project, which was greenlit by the Human Frontiers in Science Program Organization in 2023, received $1.2 million, with an additional $273,000 to fund the participation of Ukrainian scientists whose work was impacted by the war, an initiative supported by the European Commission. It’s a collaborative project that spans countries and labs, starting with the team’s field visit to Panama in March and a lab visit to Germany in June.

— — —

After being carefully untangled from the mist nets, each bat was placed in a felt bag and hand-delivered to the visitor center-turned lab space where the SELFCURE team was set up for the week. “Where’s Rachel? We have something interesting!” someone shouted as the double doors to the lab burst open. Maryna, who had been mostly quiet on the trip, rushed in holding a felt bat bag. She gingerly took out a striped hairy-nosed bat (Gardnerycteris crenulatum), a rare capture for the Smithsonian Bat Lab (and, according to Rachel, “just such a cute bat”) with impressive ears and an even more impressive nose. Everyone crowded around.

“Ooh, hi! That is beautiful!” Rachel cooed. Rachel said that to prepare for the field season, Maryna made her own key to Panama’s bats, updating it as she learned how to identify each species. “I’ve never had a student do that before,” she said. “Maryna has been so enthusiastic in her approach to learn these new species, and to master the many new sampling techniques this project entails. For a very early career researcher now in a totally new country, it is amazing to see this level of dedication and expertise. Her passion for bats has transcended language, country, and continent, and immediately connected her to our team here in Panama.”

Ralph, too, has been impressed by Maryna; he says that her years of bat rehabilitation, feeding, and handling have made her one of the most skilled wing scanners. Ralph’s goal is to use the unique collagen and vein patterns in the bats’ wings to train artificial intelligence (AI) to differentiate individuals from one another. Current technology allows AI identification of animals based on visual fingerprints like fur patterns. “We can already use AI to automatically identify individual animals by other characteristic morphological markers and some species even by their gait. Engineers are able to develop incredibly powerful tools for individual identification,” Ralph said.

Ralph hopes that eventually, this technology will be able to identify bats based on backlit photos and videos of their wings as they fly. Currently, scientists have to capture each bat, implant a small RFID tag under its skin (Radio Frequency Identification tag, similar to what’s used for pets), and recapture it to identify the bat down to the individual level. This process, known as mark and recapture, can be costly, invasive, and stressful for the bats, especially the smaller species. “This wing scan technology has the potential to vastly change the field of bat biology and our ability to understand natural behaviors in the wild, not just in this project, but across bat research worldwide,” Rachel said. “If these wing scanners can be developed to identify individual bats in the wild with high accuracy, this identification method could be a game changer for how we approach bat research going forward.”

— — —

At Ralph’s Behavioral Ecology and Conservation Lab at Nürnberg Zoo in Germany, Alona Shulenko and Valeriia Bogodist, the Ukrainian scientists on the grant who weren’t at the initial field season in Panama, met with Maryna, Kseniia, and Ralph’s team of engineers. Alona graduated with her bachelor’s in biology and is about to start a master’s program, and Valeriia has a master’s degree in veterinary science and is a current PhD student splitting her time between Finland and Ukraine. During their trip, they familiarized themselves with the wing scan technology by practicing with the bats in the Zoo’s greenhouse and strategized the upcoming complex fruit choice experiments.

While the scientists at the Ukrainian Bat Rehabilitation Center are well-versed researchers, they explained that with so much time and energy focused on rescue and rehabilitation, staff often don’t have time to test and follow-up on the behaviors they observe in their bats. “Here, we have the facilities here to improve our bioacoustic and machine learning skills,” Alona said. “It’s a huge level up for us.” Alona, who wears a black glasses chain decorated with bats, is from a small town even closer to the Russian border. “It's still not under occupation. I don't know why, but it's good luck for us,” she said. She now lives in Kharkiv and described the situation in the city in 2024 as “quite terrible.” Daily blackouts and airstrikes characterize life in the region: “Each day, you just wait for your rocket.”

For Alona and Valeriia’s families, relocating was cost prohibitive, and it would have been challenging for their parents to find jobs in another part of the country. “Of course, we have plans B, C, D, and E, for where we can evacuate our animals, our scientific collections, ourselves, and so on, but all of us are in love with this city, with our jobs, and with our families,” said Alona. “And your rocket can find you anywhere,” she added.

At the beginning of the full-scale invasion, when Alona was 20 years old, she and her mother discussed if they would leave. “We just had a conversation that, okay, we are adult women, and we can make our own choices. And my mother said, ‘I choose to stay here, and I take the responsibilities [of that decision] on my own.’ And I decided I also wanted to stay in Kharkiv and continue my work. And we just understood each other. And tried to support each other.”

A year into the invasion, Alona received a scholarship to study in Poland for six months. “Even if you’re somewhere in a safety place, you’re still worried about your animals, your friends, your work, your family,” she said. While in Poland, she felt isolated from her community. “I was really alone without anyone. It was really hard to integrate in a new society,” she said, especially where she didn’t speak the language.

Five months into her scholarship, Alona’s grandfather, who lived with her mother and sister, was killed during a Russian bombardment. “It was unexpected and heartbreaking,” she said. She moved back to Ukraine immediately to be with her family.

“I was worried a lot when I was in Ukraine and prepared for this trip. But now I feel extremely good in this safety place,” Alona reflected. Although the nightmares don’t stop when she’s away from Ukraine, she’s enjoying her time in Nürnberg. “I think the most important thing is that we feel safe, not only because we’re outside of Ukraine, but also because we’re a part of a great team with amazing people.” Alona joked, “When we’re here, we feel like small princesses.”

— — —

After a few hours of catching bats, Maryna and Kseniia headed to the dining hall for their dinner shift. Over ensalada de feria de Panamá, which Kseniia said was nearly identical to a Ukrainian beetroot and potato salad, she spoke about the differences between Panamanian and Ukrainian bats. With a 40 cm wingspan the greater mouse-eared bat (Myotis myotis) is Ukraine’s largest bat; on BCI, the spectral bat’s (Vampyrum spectrum) wingspan can reach nearly a meter long. What struck Maryna and Kseniia most, though, was Panama’s diversity: in all of Europe, there are roughly 50 species of bats. In Panama alone, there are over 120. “It’s every bat scientist’s dream to come to Panama. This is where the real bat biodiversity is,” said Kseniia.

Kseiina, who is from Kharkiv, was living in Switzerland at the time of the invasion with her now husband, Nicolas Fasel, who is also a bat researcher. She struggled being so far from her family and friends in Ukraine and the inconsistency of existing physically in peaceful Switzerland but feeling mentally and emotionally under siege in Ukraine. “[My work] felt more like a luxury. So, I had this thought, should I continue with research?”

At this point, she saw the call for Ukrainian bat scientists to join the SELFCURE project. Their group met to discuss who among them would apply. “I was thinking to myself, ‘Maybe you’re a bit tired from what you were doing before, but you should still keep going. Your expertise is needed.’”

Unlike Kseniia, the others in the group – Maryna, Alona, and Valeriia – were working at the Ukrainian Bat Center when Russia began its full-scale invasion in February of 2022. At the time, the Center had thousands of bats in their care: more than 2,500 in refrigerators in artificial hibernation, more than 1,000 in hibernation in outdoor enclosures, both groups awaiting release in the spring, and about 100 in lifelong rehabilitation too sick or injured to be rereleased into the wild. They also had thousands of bat carcasses and skulls in storage for research – the latter of which Maryna studied for her thesis.

“We woke up with war, and the first thought was, what are we going to do with the bats? And your government tells you, okay, you decide what you do,” Kseniia said. Initially, they transported the collections from the Center to their private homes in case they were unable to return to the office. “Anton’s flat became our bat rehabilitation backup bunker. Except we didn’t have real bunkers, so you had to protect yourself.”

She noted that the first month was the most intense and chaotic: public transport was down, subway stations were being used as bomb shelters, citywide curfews were at 4PM, and taxis were extremely expensive with fuel shortages and the danger of driving through the city with active airstrikes. “You have to think about how you organize your daily routine, whether you get food, whether you evacuate yourself. But first of all, you have to take care of bats. And the brave team decided, okay, we’ll stay here to take care of bats.”

“I don’t even hear the air sirens anymore,” Maryna said. Maryna, who has been working at the Center since 2019 (it was “love at first sight” with the bats, she said), is from a small town in the Kharkiv region where her parents, several siblings, and menagerie of animals live–including ten cats her family has rescued since the invasion began. She moved to Kharkiv at 17 to attend Karazin Kharkiv National University, one of Ukraine’s top three universities, where she graduated with a degree in biology in 2023. Since the COVID-19 pandemic then the 2022 invasion, classes have mostly been online, Maryna says. It’s hard for her to make the two-hour trip back home now, as transportation is unpredictable with road closures and curfews.

There were no graduation ceremonies, as mass gathering events are seen as targets and still aren’t allowed; “I just passed my exams and then went to work,” she said, getting her diploma in the mail a few months later. Kseniia missed her own undergraduate ceremony, but for an entirely different reason: she was on a field expedition outside the city to collect samples from bats, and didn’t want to leave the field to miss any time with her research.

— — —

After collecting their data, the team released the bats one by one back into the night. Around 11PM, they were finished with the day’s work. Like the bats they study, each of the “Scientists for Scientists” grant recipients on the SELFCURE project – Alona, Maryna, Kseniia, and Valeriia – have found their own niches. Alona is interested in cognition and sensory ecology while Maryna wants to learn more about machine learning and data analysis. Kseniia is interested in how bats move across the landscape in relation to one another and Valeriia is intrigued by disease ecology and immunology. “As a veterinarian, I think that self-medication is a very important topic. Sometimes we need to learn from animals how we should be treating them,” Valeriia said.

While she is studying bat viruses and parasites for her PhD, Valeriia will travel to Daniel’s lab at the University of Oklahoma to learn more about One Health, the idea that the health of animals, the environment, and humans are interconnected. “I’m excited to spend time with all these great scientists and learn from them how to think in this way,” she said. Daniel, too, is looking forward to the collaboration. “We’re really eager to host Valeriia here in Oklahoma,” Daniel said. “It’s a great opportunity to share protocols and techniques … Successfully implementing One Health research requires integrating many different perspectives on disease.”

The members of the Smithsonian Bat Lab have already learned a lot from working with such experienced bat rehabilitators. Rachel says that even now that the team has returned to Kharkiv, they send WhatsApp messages back and forth, sharing photos of sick or injured bats in Panama to seek advice from the Ukraine team. “Our group has benefited hugely by having the Ukrainian team onboard,” Rachel said. “They have brought unforeseen expertise to the project – it has really been a joy to work together and learn from each other.”

For Kseniia, building community and connections has been a meaningful part of the experience, which has helped her feel less alone both academically and professionally. Before the full-scale invasion, Kharkiv was home to a robust scientific and academic community with more than 60 high schools and universities. Now, many professionals are being forced to leave their careers in Ukraine behind. Kseniia says that it’s important to maintain these types of trainings, opportunities, and relationships for Ukrainian students and scholars. “Isolation pushes you to give up more than anything else,” she reflected.

Kseniia and Maryna were handing out postcards, magnets, and pins of bats from the Center to their SELFCURE collaborators. When Maryna was asked how she felt about going back to Kharkiv, she responded with a laugh, “I don’t know. On one hand, I'm excited to go back to work at the Center, and to speak my native language. It’s a new experience for me to go to another country, but I really miss my cat.”

While life in Kharkiv has fundamentally changed, the staff’s love and compassion for Ukraine’s bats, who have been caught in the crossfire of Russia’s full-scale invasion, has only grown. The continued rescue, rehabilitation, and study of Ukraine’s bats is an act of hope and of resistance. While the future is uncertain, Alona’s last message is simple: “Kharkiv is still alive.”