Improper perch size, perches all of the same size (
causing insufficient foot exercise), sandpaper perches, perches that are otherwise too rough or dirty, or simple inactivity can
cause a serious foot condition in birds called pododermatitis (otherwise known as
bumblefoot).
One of the most common problems in guinea pigs is
bumblefoot, where the foot becomes swollen due to a bacterial infection, often
caused by dirty bedding.