Bat Colonies in Florida – Benefits and Concerns
Bat Behavior and Potential Bat Problems
The bats present in the state of Florida are predominantly Mexican/Brazilian Free-tail bats and can cause some real bat problems.
[Tadarida brasiliensis], often living together with smaller numbers of Evening Bats [Nycticeius humeralis]). These animals are extremely social and tend to roost in large colonies (up to 20,000 or more). They live for 30-35 years and each female typically has one offspring per year (occasionally they have twins). They are very territorial and babies born on a site tend to consider it their “home”. As a result, they are persistent in their attempts to return. Typically, we find that bats excluded from a particular building on a complex or from a particular area of a building will simply relocate to the nearest convenient aperture or structure in the vicinity.
It should be understood that bats are generally extremely shy, docile mammals. They do not carry many diseases and they do not generally fly into people’s hair or make unprovoked attacks. They are extremely beneficial to the environment. In the northern hemisphere they make-up 25% of the mammal population and in the southern hemisphere, this increases to 50%. In Florida, the micrchiroptera that make up the bat population consume billions of insects (including mosquitoes) every evening. Each bat will eat 2-3,000 insects per night (this is why they are protected by state law). While it is true that bats can carry and transmit rabies, this risk is recognized as being limited (see below). That said, large colonies of Free-tail bats (and others) can and do cause problems for people when they co-exist in the same places. The smell from the excrement and urine and the subsequent staining on buildings and structures is a concern. The build-up of waste products in voids can be excessive with the attendant odor and possible health risks, the most serious of these being histoplasmosis (see below). Bat urine is very corrosive and can eventually cause damage to the waterproof membrane beneath the tile, shake or metal roof covering, where they often make their roosts.
Histoplasmosis is a fungal disease, from the histoplasma capsulatum fungus that is associated with bat guano (feces) deposits. Once inhaled, it grows in the lungs and can ultimately lead to a chronic respiratory condition.
Rabies can be contracted as a result of contact between infected saliva or nervous tissues and the mucous membranes found in the eyes, nose and mouth. It can also enter the body through open wounds. However, it is almost always transmitted by a bite from the infected animal. Although a minute number of cases of airborne infection have been reported as having occurred in cave environments, none have been recorded as having occurred in man-made structures. Only a very small percentage of the bat population is thought to carry the disease.