Bats (Chiroptera) can be found on every continent except Antarctica. There are more than 40 species of bats in the United States, 15 of which can be found in the Pacific Northwest. The most common of these is the Little Brown Bat (Myotis lucifugus).
For centuries, bats have been the subject of negative mythology, but in reality they are useful predators and help to control insects preserving the natural balance of their environment.
Bats were once very numerous in the United States, but recently, populations east of the Rocky Mountains have been afflicted with white-nose syndrome, a disease caused by a white fungus that grows on the bat’s skin and eventually kills its host. Researchers are unsure exactly how white-nose syndrome kills. White-nose syndrome has been associated with over 5 million bat deaths and is slowly making its way west across North America.
Did you know? Bats are the only mammals capable of true flight.
All bats have external ears, which they use to hunt, and have soft fur on their bodies that can range in color from red to tan to brown to grey. Bats range in length from 2.5 inches to 6 inches from head to tail. Instead of arms, they have wings made of a bone structure similar to that of the human hand. Between these bones is a thin membrane called a patagium, which allows bats to have free flight.
Did you know? Bats can live more than 30 years and fly at speeds of 60 mph.
Bats can live in a variety of habitats including deserts, woodlands, caves, suburban communities and cities.
Bats roost in rock crevices, tree hollows, mines, caves and a variety of anthropogenic structures. Some bat species have specific roosting requirements that are determined by physiological demands, predation pressures, social structure or morphology.
Development and Family Structure
Most bats give birth to a single baby which is unable to fly for several months. Babies cling to their mothers until they are too big to be carried, and are then left behind in a nursery colony while the adults hunt.
All bats in Washington State are insectivores, and usually live around fresh water where insects are plentiful.
Did you know? A single bat can consume up to 2,000 mosquitoes in one night.
Because they are nocturnal, they hunt at night and roost during the day in trees, bat boxes, under eaves and in buildings where they can gain access through open spaces in roofs, attics or walls.
Most active in the spring and summer, many bats migrate or hibernate during the winter.
Did you know? Contrary to popular belief, bats are not blind and they don’t get entangled in people’s hair. They have fairly good eyesight, but do navigate and find food primarily by using a sonar-like system called echolocation.
White-nose syndrome (WNS) is a devastating fungal disease that has been decimating the bat population in the United States. First seen in eastern New York in winter of 2006/2007, the infection has since spread to 28 states and provinces. It was thought that the disease’s westward spread had stopped in Arkansas and Missouri, but in March of 2016 a bat with White-nose syndrome was found in North Bend, Washington.
US Geological Survey microbiologist David Blehert first identified the fungus, Pseudogymnoascus destructans, which causes the disease. WNS is named for the fuzzy white fungal growth that is sometimes observed on the muzzles of infected bats. The fungus invades hibernating bats’ skin and causes damage, especially to delicate wing tissue, and physiologic imbalances that can lead to disturbed hibernation, depleted fat reserves, dehydration and death.
White-nose syndrome is transmitted primarily from bat to bat, and at this time there is no information indicating that people or other animals have contracted the disease. In order to prevent human-assisted transmission of the disease, people are encouraged to avoid caves, abandoned mines and other places where bats hibernate. Cavers should follow the most current decontamination protocol, which can be found on the White-nose Syndrome website, in order to avoid spreading WNS.
Living with Bats
Accessible attic spaces, which are often warm and dark, are sometimes used as nurseries until the babies are old enough to fly on their own.
Bats and rabies
Healthy bats prefer to keep their distance from humans. Bats can be rabid, although this is an exaggerated danger. That said, there are rare instances of rabid bats biting humans and other animals.
Never attempt to pick up a bat with your bare hands. If you find a sick or injured bat, contact PAWS Wildlife Center (if you live in King or Snohomish Counties in Washington State) for assistance, or if you live outside of Western Washington, find your local wildlife rehabilitation center.
There are only a very few cases in the U.S. of rabies transmission from bat to human. Possible signs of rabies in bats include activity during daylight hours, and the inability to fly. If a bat is around people and the noise of human activity (all of which a healthy bat will avoid), that is another possible sign the bat may have rabies. Rabid bats may also be lethargic, which unfortunately renders them docile and approachable.
If you come into contact with a bat
If you or a domestic animal in your care is bitten, or if material such as saliva or spinal cord contents comes in contact with your eyes, nose, mouth or a wound of any kind, wash the area thoroughly with soap and water and seek medical advice immediately.
Some bats will bite and not leave any marks. That is why it is crucial to seek immediate medical advice if you awaken and find a bat in your living area, near a child, or a disabled or impaired person. If you think a pet has been similarly exposed, immediately take the animal to a veterinarian.
Bats in your living space
Like other wild animals, bats sometimes find their way into buildings. They do not chew or dig their way in, but squeeze through cracks and holes less than an inch in diameter. Damage caused by bats is usually minimal, but the smell of their droppings can be offensive.
If you discover a bat in your living space:
- Remain calm and, if possible, close the bat into a room away from people and pets.
- Call your local Public Health Department and ask if there is a need to have the bat tested for rabies.
- Once the bat is gone, determine how he entered, checking for possible entry points around door and window casings, air conditioners, vents and chimneys. If you are sure there are no other bats in the house, seal all holes and cracks.
If you suspect that a colony of bats has taken up residence in a wall or attic space, watch for bat activity at nightfall and look for telltale signs of accumulated droppings below the entry.
Strategies for bat-proofing
Allow the bats to leave on their own. Do not use repellents because they will drive the animals further into the house. From May until late August, assume there are young bats in the space and wait until the babies are old enough to fly out with the adults.
At the end of the summer when you are certain there are no more young, begin excluding the bats by closing off all available entries but one. Fit the open hole with a one-way door with a hinged flap so that bats can escape but not re-enter the space. Leave this in place for several days, continue to watch for bat activity, and if possible inspect the space until you are certain they are gone.
Permanently exclude bats by sealing all possible entries. Caulk any cracks during warm, dry weather when cracks are the widest. Use weather stripping to seal spaces around doors, windows, and vents, and replace loose boards and roofing materials. Be sure to secure every crack and hole in outside walls, eaves and roofs.
Bats Northwest. January 6, 2016. Meet Our Bats
Feldhamer G.A., Thompson B.C. & Chapman J.A. (Eds). (2003). Wild Mammals of North America, Biology, Management, and Conservation (2nd ed.). Baltimore MD: The Johns Hopkins University Press.
National Wildlife Federation. January 6, 2016. Wildlife Library -- Bats
Washington Department of Fish and Wildlife. January 6, 2016. Living with Wildlife: Bats
White-Nose Syndrome. January 6, 2016. About white-nose syndrome