Bats are a definite part of the natural environment in San Francisco, actively flying and foraging across the city’s open spaces. These nocturnal insectivores perform an important ecological function by consuming large quantities of flying insects every night. Their presence is a normal sign of a functioning ecosystem, often going unnoticed. Understanding local species and how to coexist with them ensures the protection of both the animals and the public.
The Definitive Answer: Bat Species Found in San Francisco
The San Francisco Bay Area is home to a diverse group of bats, with several species regularly documented within the city limits. Among the most common are the California Myotis, the Pallid Bat, the Big Brown Bat, and the Mexican Free-tailed Bat. These local populations are entirely insectivorous, consuming moths, mosquitoes, and other flying arthropods.
The California Myotis is one of the smallest species, typically weighing only a few grams, and is known for its pale fur and ability to forage close to the ground or over water. The Pallid Bat is easily identified by its large ears and yellowish-brown fur, and it hunts larger prey like scorpions and ground-dwelling insects directly on the ground. The Big Brown Bat is a larger, robust species that is highly adaptable to urban environments, often roosting in human-made structures.
Where to Find Them and Seasonal Behaviors
Bats utilize specific natural and urban spaces for roosting and foraging, concentrating their activity near large parks and water sources. Areas like Golden Gate Park, the Presidio, and Fort Funston are known bat habitats, providing necessary tree cover and open foraging space. They are frequently observed flying just after sunset near bodies of water, such as Stow Lake, where insects are abundant.
Their activity is strongly seasonal, with summer being the peak time for visibility. Females form maternity colonies during the warmer months to give birth, typically between late spring and early fall. During this period, colony numbers swell, and bats are more active as they hunt to feed their young.
San Francisco’s mild winters mean that local species may not undergo the deep, prolonged hibernation seen elsewhere. Many enter periods of torpor, rousing to forage on warmer winter nights when insects are still available. Roosts are found in natural crevices, under tree bark, and in the attics or eaves of older buildings, which offer the quiet, stable thermal environment they require.
Ensuring Safety and Respectful Coexistence
The probability of a bat carrying rabies is very low, but the virus is present in the local population, and the disease is virtually always fatal once symptoms appear. The most important safety rule is to never touch a bat, even if it appears injured or dead. Any bat found on the ground or acting erratically during the daytime should be treated with extreme caution.
If a bat is discovered inside your home, contact the San Francisco Department of Public Health (SFDPH) and Animal Care and Control (ACC) immediately for guidance. The SFDPH investigates potential human exposure, while ACC can safely remove the animal for testing if necessary. Keeping pets’ rabies vaccinations current is a preventative measure against accidental contact with wildlife.
All bat species in California are classified as “nongame mammals” under the California Fish and Game Code, meaning they are protected by law and cannot be harmed or killed. If bats are roosting in an attic or wall void and need removal, only humane exclusion methods are permitted. This process involves installing one-way exit devices that allow bats to leave but prevent re-entry. Exclusion must not be performed during the maternity season (roughly April 15th to August 15th) to prevent trapping non-flying young inside the structure.