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 It is home to more than 250,000 volumes, including many priceless, historical documents and first editions.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.