Park Science

Bat Surveys

Bats are critical to ecosystem function however very little is known about bat species in all three parks.  Past bat surveys within the parks were sporadic and patchy, and no organized comprehensive survey had been conducted.  Bat species list, at the time, were based only on distribution maps from field guides and past surveys.  The inventory of bats involved different combinations of monitoring techniques specific to each park due to unique needs and environmental conditions.  Because sampling bias exists in all survey methods, a combination of acoustic monitoring, night and day roost surveys, and mist netting was implemented.  The Anabat system of automatic acoustic detection was used to remotely monitor locations and to determine potential mist netting sites.  Since some bats do not emit loud signals (e.g. pallid bats), mist netting was used to detect their presence.  Additionally, roost surveys were conducted during the day, especially in areas with high levels of nocturnal acoustic activity.  Bridges, buildings, cliff faces, hollow trees, mines and caves were surveyed for presence of roosts.  Roost searches are the only reliable method used to detect certain species, such as Townsend’s big-eared bat, a species in decline in California.  For positive species identification at roost sites, bats were captured with hand nets or with mist nets at emergence.  Information resulting from the inventory were used to assess population status.