Bats can carry dangerous diseases yet rarely fall ill themselves, and scientists have long wondered why.
A new study of more than 500 species of vesper bats has offered an important clue.
Researchers discovered that these bats have two separate sets of antibody genes.
Antibodies are proteins that the body uses to recognise and attack germs.
Having two sets of these genes is an immune arrangement never before seen in any mammal.
This unusual system may give bats extra tools to fight off infections.
Understanding it could help scientists develop new treatments for humans.
Once again, animals are teaching us surprising lessons about health.