Bats are small flying mammals. 25 Species of bats are found in California, almost all are insectivores. They feed on night flying insects making them an important part of the environment. Several species frequently use man-made structures such as attics, barns, or bat boxes for roosting sites and are the species you most likely will find in urban areas.
Bats have relatively long lives—5 to 30 years depending on the species—and are among the slowest reproducers for their size of any mammal. For example, the little brown bat, the most frequent user of artificial bat habitats in the United States, can live for 3 decades with the female giving birth to 1 pup per year.
As mammals, bats have fur, give birth to living young, and provide their young with milk. In spring, female bats form colonies to give birth and rear young. Roosting sites include buildings, bridges, or other structures as well as caves or tree cavities. Adults leave roosts at night to forage for insects. Young bats develop rapidly, and most are able to fly within a month or two after birth. Generally males and females with young will roost separately, but in late summer or fall, males might join the colony, and bats might migrate to warmer areas or hibernation roosts in the winter when insects are scarce.
Bats are excellent flyers and navigate using echolocation to capture insects in flight during the night. Because bats consume large numbers of insects, some people have installed bat houses with the idea that colonizing bats might control mosquitoes or other pest insects.
Although bats provide benefits by feeding on insects, they also can carry diseases to humans and other animals. You can greatly minimize the risk of disease transmission by never handling bats, not breathing dust from bat droppings, and vaccinating your dogs and cats against rabies. It is very important to educate children never to touch a bat, dead or alive. Bats also create unsanitary conditions when their droppings and urine accumulate beneath roosts, creating odors and attracting insects.
Rabies is a viral infection of the central nervous system that causes inflammation of the brain, and sometimes the spinal cord, in humans and other mammals. Once symptoms appear, the disease is almost always fatal. A rabies exposure requires contact with an open wound, abrasion, or mucous membrane—such as the eyes, nose, or mouth—and a rabid animal’s saliva or nervous tissue. Non-bite exposure to the virus is extremely rare, and no evidence exists of transmission through contact with urine or feces.
The threat of rabies is virtually nonexistent for anyone who vaccinates all family dogs and cats, avoids contact with unfamiliar animals, and never handles wild mammals. Any bat or other wild animal that you can catch is likely to be sick, so only an expert should handle them.
Like all mammals, bats can contract rabies, but even rabid bats rarely bite except in self-defense. However, the odds of a rabies infection in a sick bat—those most commonly handled by the public—are higher. Overall, the odds of being harmed by a bat are remote for those who don’t handle them.
If you are accidentally bitten while handling a bat, make sure you save the mammal for examination and contact your county health department. Immediately wash the bite with soap and water, and seek prompt medical advice. A non-bite exposure should be treated in the same manner as a bite.
The fungus Histoplasma camsulatum capsulatum causes the respiratory illness histoplasmosis. The fungus occurs naturally in the soil in warm, humid areas, and bat and bird droppings enhance its development. Human infection occurs by inhaling the fungal spores that disperse when dry fecal deposits are stirred up. Bird roosts are the most important sources of the infection, and more than 99% of all cases in the United States are found in the Ohio and Mississippi river valleys. This disease rarely has been reported in California. The fungus normally doesn’t survive in hot, dry attics. However, to reduce risk of exposure, persons cleaning up either bat or bird droppings should wear proper personal protective equipment including respirators that filter particles as small as 2 micrometers. In some situations a wetting solution can help keep dust down.
Parasites are organisms that feed on other animals. Bat parasites include fleas, flies, true bugs, chiggers, ticks, and mites. Most bat parasites are host specific and can’t survive on other animals. No evidence exists of disease transmission to humans or domestic pets from bat parasites. Parasites that remain after bats have been removed from buildings soon die without their hosts.
If you suspect bats are roosting in your building, you’ll need to carefully look for signs of them. Bats can squeeze through openings as small as 1/4 inch. Cracks around windows, doors, pipes, electrical wiring, or vents can provide access. Being alert to off odors or to droppings beneath openings can help you locate roosts and entry points. Return late in the evening, just before dark, to observe how bats are gaining entry into a building by watching where they fly out. Exclusion is the primary way to manage bats, but you’ll want to be sure all bats have left the structure before you seal it up completely.
Large numbers of bats living in attics or walls are undesirable. Most bat colonies are small and go unnoticed for years, but when odor or noise increases or bat droppings accumulate, eviction and exclusion are the only safe and permanent remedies.
Entry points of large colonies usually are quite obvious. When bats start emerging at dusk to feed, watch the building to see where they exit. Daytime inspection should reveal the holes or cracks they are using. Often, these will be beneath eaves, around the chimney, around air and plumbing vents, near loose boards, beneath roof caps.
You also can identify the location by looking for staining caused by body oils (similar to rodent “rub marks”), bat urine, and bat droppings. Bat droppings, known as guano, crush easily, revealing shiny bits of undigested insects.
You’ll want to avoid bat control when flightless young could be present, usually May through September in California. Excluding the parents will starve the young and create odor problems and an infestation of flies. Most bats leave in late fall in most areas, making winter an ideal time to implement bat control exclusion techniques.
Using netting is a relatively simple technique to exclude bats from a structure. Using polypropylene bird netting and hanging it over the exit point of the bats will allow the bats to leave. After about 7 days remove the netting and seal the openings with minimal expansion foam.
Another method of bat control involves using a plastic tube, which the bats can fly out of but cannot fly back into. Wait 7 days remove the plastic tube and seal the opening with minimal expansion foam.
Contact Wildlife Removal Services for all of your Bat control / prevention needs in San Diego. We specialize in bat removal, bat eviction, and bat exclusion repairs. We follow all state and federal laws regarding the control and prevention of bats on your home or business.