The Joanina Library of the University of Coimbra Alta and Sofia is one of two Portuguese libraries to house colonies of bats as natural deterrents for bugs that would otherwise feed on old books and manuscripts.

As unusual as having a colony of Common pipistrelle bats living behind the bookshelves of one of the most beautiful libraries in the world, the curators of this historical marvel swear that the flying rodents provide an indispensable service – they feast on bugs that would otherwise damage or feed on old books. And with some of these ancient manuscripts being virtually priceless, it’s no wonder that the bats are regarded as helpful guardians.

Photo: Jeremy Bezanger/Unsplash

There are many bug species known to gnaw on paper, and they pose a major danger to libraries like Joanina. Thankfully, the bats that call this place home act as a form of natural pest control. They are nocturnal, so they don’t bother library visitors during the day, but as soon as the sun sets, they start coming out from behind the old book stands and catch insects right before swooping out of the building through the open windows.

No one knows when the colony of Common pipistrelle bats moved into the Joanina Library, but many believe that they’ve been around since the opened, hundreds of years ago. Records of their presence here can be traced back to at least the 1800s.

The small bats of Joanina Library are a famous attraction, but what most people are always curious about is what happens with all the droppings that bats usually leave behind. This is something that the library has been dealing with for centuries. Every evening, the original 18th-century furniture is covered with animal skins, and in the morning, the floors are scrubbed by the cleaning staff. The mess they make is considered a small price to pay for the service they provide.

Because the bats are nocturnal, it’s hard for visitors to catch glimpses of them as they are visiting Joanina Libray, but some say that waiting on the steps leading from the library to the nearby cobbled square on any given night you are bound to see the rodents flying out of or back into the building.