Question

Passage

Deep beneath the rugged Chihuahuan Desert of southern New Mexico lies Carlsbad Caverns, a spectacular labyrinth of more than 119 known limestone caves. Formed not by the typical action of surface water carving through rock, but by sulfuric acid eating away at limestone from the bottom up, Carlsbad Caverns represents a geological marvel. The process began millions of years ago when hydrogen sulfide gas, migrating upward from deep oil deposits, mixed with oxygen-rich rainwater that had seeped into the water table. This reaction created sulfuric acid, which dissolved the limestone along fractures and faults, creating massive chambers.

Among these chambers, the most famous is the Big Room, a massive limestone chamber that ranks as one of the largest cave chambers in North America. Measuring 4,000 feet long, 625 feet wide, and 255 feet high at its loftiest point, the Big Room is so spacious that it could comfortably accommodate six football fields. Visitors to the Big Room are treated to an astonishing array of speleothems—secondary mineral deposits formed in caves. These include stalactites, which hang like icicles from the ceiling; stalagmites, which rise from the floor; and delicate soda straws, which are hollow, thin-walled tubes of calcite.

The discovery of Carlsbad Caverns is traditionally attributed to Jim White, a teenage cowboy who first entered the caves in 1898. Riding near the foothills of the Guadalupe Mountains, White noticed a massive dark cloud rising from the desert floor. Drawing closer, he realized the cloud was not smoke, but millions of Mexican free-tailed bats exiting a natural opening in the earth. Armed only with a kerosene lantern and a homemade wire ladder, White spent years exploring the dark passages, marveling at the formations. Although initially met with skepticism by locals who doubted his tales of a vast underground wonderland, White eventually convinced others of the cavern’s significance. His efforts paved the way for Carlsbad Caverns to be designated a national monument in 1923, and later a national park in 1930.

Beyond its geological significance, the cavern ecosystem hosts a diverse array of life. The most notable inhabitants are the Mexican free-tailed bats, which use the cave’s natural entrance as a summer home. From May through October, an estimated 400,000 bats roost in the dark recesses of the cave during the day. At dusk, they emerge in a spectacular swirling column to hunt for insects over the Pecos River Valley. Interestingly, the bats do not roost in the Big Room itself, which remains too cool and damp for their rearing needs; instead, they occupy the Bat Cave, a separate lateral passage near the natural entrance. The bat population provides a vital ecological service, consuming tons of moths and beetles each night, which helps protect local agricultural crops from pests.

Today, park researchers continue to study the caves to better understand the delicate balance between preservation and public access. The introduction of artificial lighting, while necessary for visitor safety, has promoted the growth of algae and disrupted the natural behavior of cave-adapted organisms. Furthermore, the footprints of early explorers and modern tourists alike leave lasting marks on the sensitive cave formations. Preservationists work diligently to monitor humidity levels, airflow, and carbon dioxide concentrations to ensure that this underground treasure remains intact for future generations.

In recent decades, scientific interest in Carlsbad Caverns has expanded beyond traditional geology and ecology into the field of geomicrobiology. Researchers have discovered that the cave walls are home to thriving communities of extremophilic microbes. These microorganisms, which survive in complete darkness without access to sunlight or photosynthesis, derive energy by consuming minerals like manganese, sulfur, and iron found in the cave rock. Some of these unique bacterial strains produce novel chemical compounds that have shown promise in medical research, particularly in the development of new antibiotics. This unexpected scientific frontier highlights the caverns not just as a scenic wonder, but as a living laboratory of evolutionary adaptation.

Question

According to the passage, in which specific area of the caverns do the Mexican free-tailed bats roost during the day?