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Deep within the remote wilderness of in West Texas lies Emory Cave, a hidden maternity roost for the endangered Mexican long-nose bat (Leptonycteris nivalis). Each summer, the females travel to the cave during their annual migration from Mexico, seeking refuge to raise their young. As dusk falls each evening, the elusive bats emerge to feed on the nectar of flowering agave, playing a crucial role as a pollinator of this valuable plant.
Despite the importance of their ecological role, the population of Mexican long-nosed bats has long been a bit of a mystery. Traditional methods of counting bat populations, such as surface-area estimations and mist nets, yielded inconsistent results, making it difficult to know just how many bats utilized the cave. Estimates varied wildly, sometimes suggesting numbers in the thousands, while actual counts revealed far fewer.
With the absence of reliable data on population dynamics, researchers recognized a critical gap that needed to be filled. To address this, they turned to thermal-infrared cameras鈥攁 technology that captures the heat emitted by bats, allowing for accurate counts even in low-light conditions.
鈥淚t is exciting to find and use new technology 鈥�thermal imaging and computer processing 鈥� that works so well to detect bats in complete darkness at this site,鈥� said Dr. Loren Ammerman, professor of biology at Angelo State University in San Angelo, Texas.
From 2008 to 2023, researchers from Angelo State University, the Warnell School of Forestry and Natural Resources and the Washington Fish and Wildlife Office utilized a series of thermal cameras to capture videos of bat emergences from the cave.
Over this period, 35 videos were analyzed manually alongside an automated program developed to improve efficiency in counting bats. This combination of manual and automated approaches aimed to refine population estimates and observe long-term trends without the labor-intensive nature of past methods.
The manual analysis involved watching hours of footage in slow motion to tally the number of bats emerging. In contrast, the automated program employs advanced algorithms to count bats autonomously, significantly reducing analysis time.
鈥淚 never imagined when we first started monitoring this endangered colony with emergence videos 20 years ago that counting the bats would be made so much easier with new developments in computer processing,鈥� noted Dr. Ammerman.
The , which was recently published in the Journal of North American Bat Research, revealed a much better understanding of the colony's dynamics. The maximum colony size for each year varied from 294 to 3,360 bats in July, with an average of 2,156 bats over the study duration. Notably, while yearly populations fluctuated, there was no significant overall decline鈥攁n encouraging sign for anyone interested in the bat's recovery.
鈥淎ccurate monitoring supports the protection of endangered species in many ways,鈥� said Dr. Jade Florence, the U.S. Fish and Wildlife Service species lead for the Mexican long-nosed bat. 鈥淔or the Mexican long-nosed bat, it will allow for a more accurate understanding of the number of bats using each roost and the seasonality of roost use. This can inform which roosts are most important to conservation.鈥�
鈥淭his monitoring can also help produce more accurate estimates of the total population size of the species and understand typical fluctuations in population size over time,鈥� Florence added.
The advent of this new technology aligns with ongoing federal efforts to recover the Mexican long-nosed bat. In 2024, the U.S. Fish and Wildlife Service formally published a comprehensive , which outlined specific, prioritized actions prescribed in the broader .
One of the detailed recovery actions emphasizes the need to expand monitoring for the Mexican long-nosed bat by developing a standardized program to assess roosts and foraging habitats throughout its range. This initiative is crucial for verifying the bat's long-term health and allowing for the identification of areas needing conservation efforts in response to disturbances.
The future of the Mexican long-nosed bat looks to be increasingly promising, thanks to the committed efforts of academic researchers, conservation organizations such as Bat Conservation International and the Nivalis Conservation Network, alongside the support of federal agencies like the U.S. Fish and Wildlife Service, National Park Service and the Bureau of Land Management.
These efforts show that with the right blend of technology, collaboration, and determination, we can advance the recovery of this endangered pollinator not only for the bats themselves but also for the intricate ecosystems they inhabit.
