COIMBRA, Portugal—During the day, as visitors file through the University of Coimbra’s 300-year-old Joanina Library, the creatures remain hidden behind the grand, gilded bookcases. At night ...

Since the late 18th century, small colonies of bats have guarded the books in the Joanina Library at the University of Coimbra in central Portugal. The library contains 60,000 books that are all ...

Whether the flittermice took up residence here 300 years ago, when the library was built, or more recently is unknown. Librarians do know they’ve been here since at least the 19th century; they ...

The exterior of the Joanina Library Wikimedia Commons. The floors are covered in rose, white, and grey marble tiles, and the stacks are filled with ancient manuscripts. If the library ...

The Joanina Library is famous for being one of the most architecturally stunning libraries on earth. It was constructed before 1725, but when exactly the bats arrived is unknown.

At the top of Coimbra, behind an austere façade, lies a Baroque jewel: the Joanina Library. Adorned with carved woodwork, populated by guardian bats and overflowing with ancient works, it ...

Bats have long lived in the Joanina Library and the Mafra National Library in Portugal, and they come out at night to exterminate the insects that eat the books. In This Beautiful Library, Bats ...

At Biblioteca Joanina and the Mafra Palace Library, both, curiously, located in Portugal, and both built in the 18th century, small bats, about an inch long, act as guards against book-eating insects.