Blog post

Learning More About California’s Bats

On November 1, Stanford researcher Dr. Jon Flanders gave District staff an informative presentation on bats. Dr. Flanders is currently conducting bat research at Jasper Ridge Biological Preserve, in Portola Valley. He shared his knowledge of bats in general, as well as the current findings of bat tracking in Jasper Ridge. In collaboration, the District provided him with mosquito monitoring data for the area that can be analyzed in conjunction with the bat data. 

Twenty-five species of bats occur in California.  Most cause no problems, are nocturnal, and rarely seen. However, some species will utilize houses and other man-made structures for roosts or nests. This can lead to an accumulation of droppings, and in certain instances the possibility of rabies transmission to humans.

Rabies is a viral infection of mammals that is rare but present in animals in San Mateo County. In 2015, three bats in the county tested positive for rabies. It is important never to handle a bat, especially if it appears ill or is out during the day.

Bats that appear sick, injured or dead should be reported to the Peninsula Humane Society at 650-340-7022.  These bats can be tested by the County Health department for rabies. Anyone who has been in contact with a bat or finds a bat in their room upon awakening should seek medical care for rabies shots because of the possibility of being unknowingly bitten. 

A single bat found flying in a home or other building can often be encouraged to fly back out by opening all doors and window to the outside and closing off entrances to other rooms. Bats that are repeatedly entering or nesting within a building need to be excluded. This work should be done by a wildlife professional who is experienced with safe handling of bats and is familiar with regulations and practices that prevent bats from entrapment and recognize their seasonal life cycle.