Influence of weather on life history characteristics of two bats, Myotis lucifugus and Myotis keenii at Gandall K'in Gwaayaay, Haida Gwaii (British Columbia)

Life history characteristics for populations of Myotis keenii and M. lucifugus occupying hydrothermally heated maternity roosts at G&barbelow;andll K'in Gwaayaay (Hotspring Island), Haida Gwaii (Queen Charlotte Islands), British Columbia were determined during 1998, an abnormally warm, dry summer and 1999, an abnormally cool, wet year. Light traps were used to monitor the relative abundance of aerial insects. For M. lucifugus, parturition was early and synchronous in 1998 but late and asynchronous in 1999, while the reverse was true for M. keenii. Myotis lucifugus preyed on Lepidoptera and medium to large Diptera during both years, while M. keenii fed on Lepidoptera and arachnids, demonstrating their ability to glean invertebrates off vegetation. Lepidoptera and medium to large Diptera were less abundant during early 1999, while micro-Diptera were much more abundant. The different responses by the two species to the different environmental conditions appeared to be due to differences in their foraging behaviour.