Acta Univ Latv (2008) 745: 43–52

Late summer and autumn swarming of bats at Sikspārņu caves in Gauja National Park

Abstract

Late summer and autumn swarming of bats at underground hibernacula has so far been poorly investigated in the north-eastern part of Europe. This study was conducted at Sikspārņu caves in Gauja National Park in 2005 to 2007 with the main aim to determine the species composition of swarming bats and the swarming phenology for different species. Mist-nettings of swarming bats were performed once per fortnight from the end of June until the beginning of November. Altogether 3,448 bats of seven species were caught of which Myotis daubentonii and M. brandtii were the most numerous. For all species adult males predominated initially, but numbers of adult females and subadult individuals increased as the season progressed. The capture-mark-recapture method revealed an individual-specific trend of visitations by adult males of M. daubentonii in subsequent swarming seasons. Migration between different swarming and hibernation sites located at 5- to 21-km distances were also recorded.