Bats, the conquerors of the dark, value their caves just like Batman treasures his Gotham city. For some at least, these enclosed dark spaces might seem claustrophobic. But, for 48.5% of 1,400 species of bats, these areas are what they call home. They provide safety, stability, and a suitable environment for hibernation, mating and reproduction. Do these caves serve different purposes in different seasons? Do species differ in how they use such caves for hibernation or reproduction? If they do, then conservation strategies would need to be tailored to meet specific needs of each species while also prioritising caves or habitats that provide maximal conservation output.

A recent study from the National Centre for Biological Sciences (NCBS-TIFR), Bengaluru, published in the Journal of Zoology, sheds light on how bats in the central Himalayas use caves differently depending on seasonal changes. The researchers found that small changes in outside temperatures could alter the temperature within these caves during different seasons, and bats may be able to track such changes in temperatures to optimise energy conservation during hibernation and reproduction.

The research team set foot into 41 limestone caves in Nepal’s Gandaki province in central Himalayas, moving from lower to higher altitudes (400 — 2,700 metres) across seasons (mid-winter, late-winter and early-spring) in search of the dark knights. They visited the caves three times during each phase to increase accuracy. They took care to minimise disturbances- using red torches to avoid startling the bats and reducing noise as much as possible. Bats were not captured for the study, ensuring that they weren’t disturbed during these sensitive periods of hibernation and reproduction. The ecological significance of the caves were also studied using the Bat Cave Vulnerability Index (BCVI). It looks at both the number and types of bats in a cave and the dangers they face and converts it into a score to decide which caves need the most protection.

“Changes in air temperature outside the caves can affect the temperatures inside, especially near the entrance, while deeper areas remain more stable”, says Sanjeev Baniya, the lead author of the study.

What’s interesting is that even though the deeper parts of caves offer a steady climate, bats in the central Himalayas tend to avoid them during winter, by heading towards the lower elevations where they could find food more easily. But when the spring arrives, they come back to these deeper quiet spots to raise their young ones. As a result, the species composition within caves shifts with changes in seasons indicating that bats possibly track insect activity, much like Batman moves from Gotham city to other quieter towns based on the crime rates.

Himalayas warm faster than the global average. This could lead to disrupting the microhabitats within these caves. Bat species in the central Himalayas show very distinct patterns in their cave use on seasonal terms based on factors like cave structure, elevation and temperature. For example, Hipposideros armiger and other bat species chose warmer spots while Rhinolophus luctus chose colder areas within the caves. 

Other than the seasonal impact, human activities add to the need for conservation too. For centuries, caves were not just bat shelters but also held religious and cultural significance, as centers for meditation, places of worship, and sanctuaries for monks. They are also noticeable tourist attractions. The artificial lights, noise pollution, presence of visitors, mining activities and construction works can directly or indirectly disrupt their microhabitats, turning these caves less preferable as a roost or home. 

Have you ever wondered what would happen if bats disappeared?

Well, let me start by stating this;

Their decline will not just be theirs, it will be ours too.

Bats act as pollinators and seed dispersers, supporting regeneration and replenishment of nature itself. They serve as pest controllers and are involved in nutrient cycling. Any disturbance in their environment would ultimately disrupt our lives too.

“Different bat species show seasonal preferences for specific microclimates. Warmer sites in spring, for example, are chosen to support reproduction. However, even small changes in temperature due to climate change can increase the energetic costs for bats, affecting their ability to save fat or energy during hibernation. If such variations occur in the caves they rely on, they might deplete the stored fat before the reproduction phase thus risking their survival and overall fitness”, says Baniya

Hence, this study calls for targeted conservation strategies based on a seasonal approach. Year round methods are important, but only with consideration towards their seasonal preferences during periods such as hibernation and reproduction. Restricting human activities during such crucial times could help in maintaining life within the caves. Data from BCVI, calls for legal action, patrolling and regulation of tourism to safeguard these underground sites. Long term investigation and protection of these caves are essential, not just for the survival of bats alone, but also for maintaining healthy ecosystem functioning. As cave dwelling invertebrates and vertebrates rely on bat guano, bats, directly, act as keystone species in cave ecosystems. 

We’ve known bats through myths and fiction, as symbols of fear and darkness. While in reality, they are small, silent, winged guardians of our ecosystem. Imagine a bat as a solo traveler in search of a place called home. For us, humans, this would mean a new city, a tent under the stars, a cabin or even a room of one’s own. These places act as comfort spaces that help us grow. But the case is sadly different for bats. These bats in the Himalayas, consider their caves as their only comfort zones. Without them, survival is threatened. Hence, protecting their caves isn’t just a responsibility, rather a necessity.