A mysterious disease has killed more than a million bats in America - and it's threatening to wipe out whole species of the tiny mammals.
It's bad news for bats and for famers as the flying creatures eat LOADS of insects that damage crops and forests.
Scientists are urgently trying to work out how to stop the spread of the disease, called white-nose syndrome.
They're so worried about the disease spreading that they've sealed off some bat caves to visitors.
The disease is known as white-nose syndrome because it causes a white fungus to grow on the bats' noses, wings and ears. It's thought the fungus was brought into bat caves by tourists.
These bats in Indiana have been badly hit by the disease
It's spread to at least 16 American states and three Canadian provinces.
As well as the disease, scientists say thousands of bats are also being killed off by wind turbines.
The loss of bats could cost farmers billions of dollars as crops are ruined by insects.
So the experts are asking the American government to do something urgently to help bats.