The bat is a flying mammal that have evolved over millions of years and are the only mammal that are capable of sustained flight, and are popular in the western world with their association with vampires and evildoers.
Depending on the type of viral infection they have, bats can undergo various changes. Sometimes this means a simple increase in aggression and a guaranteed bloodthirstiness without any other noticeable differences in physiology, and other times the animal increases in size and displaying other
t-Virus characteristics such as skin necrosis and grotesque muscle development.
The most common kind of bat becomes extremely aggressive towards humans, attacking in swarms which is quite unlike their uninfected brethren. However they do have an adversity to light, even a tiny light source such as from a
Lighter is enough to prevent them from attacking.
Also, regular bats have also been encountered where there is no apparent viral infection, even in places where an outbreak has occurred perhaps demonstrating that bats do have an uncanny defence against the
t-Virus. It's unknown whether Umbrella have ever used bats in their B.O.W. (Bio-Organic Weapon) research.
