Inside the underground neighborhoods bats call home.
07.08.26
By Gabriela González-Olimón
Imagine choosing between a fancy hotel room and a small camping tent. Both are places where you can get some rest, but they feel very different. And you probably prefer one to another.
Bats face similar choices when selecting where to live. Some prefer large caves with high ceilings where they can fly freely. Others choose small, cozy spaces that are warm and damp. But bats don’t pick caves at random. The size, shape, and even the surrounding forest influence how many bats live there and how active the cave becomes. Far from silent hollows, caves are lively habitats—hidden neighborhoods where bats gather, cooperate, and interact.
Just like us, bats need a nice bedroom. Their homes, called roosts, are the spots where bats take a break or sleep, whether in caves, hollow trees, curled leaves, or even under roofs. Choosing the right roost can mean the difference between thriving and struggling.
Hot or Cool?
Caves can form in limestone, volcanic rock, or sandstone, and each type creates unique conditions for bats. One simple way to classify them is by temperature.
Cool caves remain cold and stable throughout the year. Their damp, dark air makes them perfect for hibernation (or torpor), when bats enter a deep winter sleep. These environments help conserve energy by slowing metabolism and reducing water loss. Stable humidity is especially important, since it prevents dehydration in small bats that lose moisture quickly through breathing.
Far from silent hollows, caves are lively habitats—hidden neighborhoods where bats gather, cooperate, and interact.
Hot caves, in contrast, are warmed by the bats themselves. When thousands cluster together, they can raise the temperature to between 28°C and 40°C (82°F and 104°F) creating a warm, humid, and stable microclimate. These conditions are ideal for species that need to grow and raise their pups quickly.
But temperature is only part of the story. Bats also select caves based on features such as size, humidity, light, and airflow. Larger caves tend to be more stable and often contain a variety of microclimates. Entrances are usually cooler and drier, while deeper sections are warmer and more humid.
It’s almost like a natural apartment building: some bats live near the “balcony” at the cave entrance, others prefer the “basement” deep inside, and many occupy the “middle floors.” By spreading out this way, bats reduce competition and coexist, turning caves into complex miniature ecosystems.
Sharing the Darkness
How do so many bat species live together without competing? Scientists explain this using functional segregation. This means species share nature’s resources without fighting: each uses different foods, spaces, or times of activity. For example, nectar-feeding bats visit flowers early in the evening, while insect-eating bats may hunt later at night. Some catch insects in open air, while others hunt near the ground.
Their echolocation calls differ too. By using different frequencies—like tuning into separate radio stations— species avoid interfering with one another, each carving out its own acoustic space in the night.
Mexico, for example, is home to an incredible diversity of bats. About 45 percent of them use caves as shelters, either temporarily or permanently. Some caves contain thousands, or even millions, of bats. Sometimes only one species is present, but often many species share the same cave, creating what we could call a “great bat sleepover.”
Nurseries & Winter Shelters
Caves aren’t just daytime hideouts; they are also essential for reproduction and survival. The Mexican big-eared bat (Corynorhinus mexicanus) hibernates in caves during winter. The lesser long-nosed bat (Leptonycteris yerbabuenae) uses caves as maternity colonies, where females gather to give birth and care for their young. Fruit bats, like those in the genus Artibeus, also use caves, although they often form smaller groups. These sites offer protection from predators and harsh weather, while proximity to fruiting trees ensures easy access to food.
Despite all this, scientists still do not fully understand how different bat species share caves. Each cave is like a mystery waiting to be solved.
Safeguarding Ecosystems
Despite their importance, caves face serious risks. Human disturbance, unregulated tourism, vandalism, and habitat loss threaten bats and their shelters. Noise, lights, and careless visitors can disrupt colonies, forcing bats to abandon roosts. Land-use changes and infrastructure development destroy cave surroundings, weakening the balance between underground and forest ecosystems.
Yet caves are far more than holes in the ground. They are homes, nurseries, safe shelters, and natural laboratories. Protecting caves means protecting bats, and protecting bats means safeguarding entire ecosystems. Bats may be small, but they are mighty guardians of the night, pollinating plants, dispersing seeds, and controlling insects to keep nature in balance.
Protecting caves means protecting bats, and protecting bats means safeguarding entire ecosystems.
So, the next time you see a bat tracing silent arcs across the evening sky, remember: its home may be a hidden world beneath your feet, alive with sound, warmth, and life. These caves are more than shelters; they are the beating heart of ecosystems. Protecting them means safeguarding not only bats, but the delicate harmony of nature they help sustain.
Our Research Adventure
As part of our Bat Conservation International student scholar research, my speleologist team and I explore caves in Central Mexico, especially in the Sierra de Álvarez, to learn how cave features and surrounding landscapes affect bat communities. Which caves host more species? How do bats coexist? And how can this knowledge guide conservation?
Fieldwork is an adventure: muddy boots slipping on limestone, headlamps cutting through darkness, the sudden rush of wings echoing overhead. The air smells of damp earth, and every cave feels alive with hidden stories. Each exploration brings us closer to understanding how bats sustain ecosystems, and how fragile these systems can be.
And our tools? They’re as peculiar as the caves themselves. Mist nets stretch across cave entrances like giant invisible webs, catching bats mid-flight for a quick health check. Infrared cameras let us spy on their secret nightlife. Ultrasonic detectors, meanwhile, pick up bat calls far beyond human hearing. Together, these gadgets make us part scientist, part detective in the underground world of bats.
Gabriela González-Olimón is a 2025 Bat Conservation International Student Scholar.
Gabriela González-Olimón
Diversity and Health Status of Bat Communities in a Karstic Cave System in Mexico
Special Recognitions: Verne & Marion Read Bat Conservation Honor
Wildlife populations face growing conservation challenges due to human-induced environmental pressures, which not only threaten habitats and destroy bat roosts, but also increase the potential for disease transmission across species. Understanding species’ responses to human-induced ecosystem changes is critical for designing effective conservation strategies. This project focuses on the bat community within a protected area in Mexico, where over 80 karstic caves have been reported, many of which remain unexplored.
We aim to inform strategies to protect bats and their ecosystems in areas vulnerable to White-Nose Syndrome (WNS), by addressing the following objectives: 1) Identify and evaluate the conservation status of caves as bat roosts in a human-modified landscape within a protected area, and assess the diversity and composition of cave-roosting bat communities, and 2) Assess the susceptibility of these caves to contamination with Pseudogymnoascus destructans, the fungus which causes WNS, and the potential threat to bats. We hypothesize that better-preserved caves will support a more diverse and abundant bat community, and that human and environmental changes enhance the risk of WNS by modifying bat habitats and increasing cave contamination.
Bat and cave monitoring will be carried out over two seasons using mist nets, ultrasonic detection and environmental and physical variables of the caves and surroundings to assess their conservation status. We seek to understand how bats are using these habitats and what pressures are acting over them in the context of the current spread of WNS towards Mexico, thus giving insights that are crucial to design appropriate conservation strategies.
