The Bat Libraries of Portugal

Bibliophiles aren’t the only ones that love hanging out in the library. Given the chance bats too would love to roost there and eat the bugs and bookworms that feast on old manuscripts. That’s exactly how generations of bats have been keeping safe the prized collection in two Portuguese libraries—the Mafra Palace Library in Mafra and the Biblioteca Joanina in Coimbra.

The Biblioteca Joanina. Photo: xiquinhosilva/Wikimedia

The Biblioteca Joanina, located at the heart of the University of Coimbra, is frequently considered one of the most beautiful libraries in the world. It was named after its founder, King John V of Portugal, who began constructing the library in 1717, during the onset of the Age of Enlightenment in Europe. It is home to more than 250,000 volumes, including many priceless, historical documents and first editions.

The library building was conceived as a vault, with exterior walls more than 2 meters thick, and a door of teak that keeps the interior at a constant and stable temperature of 18–20 °C. The oak wood used in the library’s structure elicits an odor that is repellent to insects that survive on paper. And of course, there is a colony of bats that hide behind the bookshelves during the day when the library is open. At night, they come out of their hiding places and feast on the insects that live among the books before swooping out of the window in search of more prey.

The opulent reading rooms of the Biblioteca Joanina. Photo: xiquinhosilva/Wikimedia

It’s not known exactly when the bats took up residence in the library, but its known that have been there since at least the 19th century. Each night before the library closes, the caretakers cover the furniture with sheets of leather to keep out bat droppings, and each morning they remove the covers and clean the floors.

The other library is in Mafra Palace located 125 miles to the south, just northwest of Lisbon. The grand library on the second floor of the palace is the jewel of the place, with a high vaulted ceiling and magnificent marbled floor. The wooden bookshelves in Rococo style are situated on the sidewalls in two rows, separated by a balcony with a wooden railing. They contain over 36,000 leather-bound volumes, attesting of the extent of western knowledge from the 14th to the 19th century. Among them, are many valuable incunabula (books printed prior to the 1500 before the printing press became widespread), such as the 1493 Nuremberg Chronicle.

Dating the colony of bats at the Mafra Palace library is hard, but they are likely around for centuries. As a tribute to these winged creatures, the library features a small glass case showcasing the taxidermied remains of three bats who were former residents.