In the daytime, they fold up their leather-like wings and hang high on the rafters with their hooked claws, resting quietly behind the magnificent gilded bookcases in the Biblioteca Joanina until dusk, when they come out to enjoy their meal.
They are the bats of the library – waiting until nightfall to catch those bugs, otherwise, these bugs would feast on the priceless treasures stored in the library.
As evening approaches, when people stream out of this 300-year-old Baroque-style building known as the Joanina Library, the staff eagerly await the bats to come out and be active. For centuries, these bats have played a crucial role in the library, considered one of the most beautiful libraries in the world, controlling pests in this stunning setting.
However, you won’t see them during your visit.
Upon arriving at the University of Coimbra in Portugal, the location of the Joanina Library, visitors are amazed by its interior décor: entering from the ancient cobblestone square of the Palácio das Escolas into the library, all decorations exude a magnificent 18th-century ambiance. Visitors will pass by a statue of the library’s founder, Portuguese King João V.
When construction of the library began in 1717, the Age of Enlightenment was already underway. The building was eventually completed in 1728, with the first books being housed in the library in 1750. Now the library holds around 70,000 volumes, focusing on science, civil and canon law, philosophy, and theology, some dating back to the 15th century. These books are said to represent the finest works of printing across the entire European continent.
Descending into the library from the square, visitors actually arrive at the library’s third and highest floor, known as the Noble Floor, adorned with magnificent gilded bookshelves. The halls on this floor are separated by towering and intricately designed arches, filled with exotic multi-colored oak shelves. Precious tropical woods from Brazil speak of the former glory of the Portuguese Empire.
The mahogany front door seals the entire structure like a treasury. Walls over 2 meters thick help regulate temperature and humidity to protect the antique books stored within.
Of course, there are also two lower levels. But when it comes to the protection of the books, there are some furry flying mammals worth mentioning.
You won’t see them. But you might hear them. According to the Smithsonian, at dusk, there may be echoes of chirps and screams or what is described as bats “singing”. If you sit outside at night, you may see them fluttering around or flying indoors seeking shelter.
While the smell of oak serves as a natural insect repellent, these bats are much more efficient in this regard. They have a voracious appetite for insects, and these insects love to feed on paper books and manuscripts. But perhaps their favorite prey is mosquitoes. The staff prefer the assistance of these insect-hunting bats rather than dealing with the pests themselves.
The only real concern is bat guano.
In a long-standing tradition, the staff knows to cover the luxurious bookcases with large leather pieces to prevent bat guano damage. This method has been proven effective in European libraries and churches for centuries. Come morning, the staff remove the leather covers and use a bit of grease to clean up any droppings on the marble floors.
The price paid to protect the priceless books is minimal.
The bat colonies have been a constant presence in the library almost since the time King João V first constructed it—perhaps when his portrait across from the mahogany front door was still new. Maybe when the frescoes depicted scenes in bright hues while the bats fluttered beneath. The central female figure on the ceiling holding a book symbolizes knowledge spreading to the four corners of the world: Europe, the Americas, Asia, and Africa.
The library boasts two-story gilded bookshelves, opulent arched doorways emblazoned with crests, six carved wooden desks, intricate carvings, and golden balconies that awe visitors. There are secret staircases hidden within faux marble-veneered arches leading to a balcony, a secret door only known to the staff that is off-limits to visitors. Guests then descend via a public staircase.
The intermediate floor is more modest, constructed of bare stone bricks. It may sound strange, but guards and wardens have been stationed here for ages. Until 1834, the university was an autonomous institution, therefore having its own royal prison. Once inaccessible to outsiders, the area now serves to showcase manuscripts and as a repository for books.
A medieval prison is situated at the very bottom of the building. Narrow cells and winding staircases form an ancient jail. This is the oldest prison preserved in Portugal. The ground floor now serves as a book deposit where items are cataloged before being placed on the main floor’s shelves.
Half a million people visit the Joanina Library each year, which is the true reason for such meticulous conservation efforts. Vehicles driving through the rising dust have altered the environment. Now only 60 people are allowed entry every 20 minutes to protect the contents inside. Visitors are limited to a 10-minute stay in the main room.
Meanwhile, a small group of creatures living behind the bookshelves continues their ongoing battle against pests. For years, the bat colonies have been indispensable and will continue to contribute their share in pest prevention.