Bats as indicators of habitat connectivity in urban environments

Sammanfattning: Human disturbances to natural environments have been an increasing issue since the industrial revolution when the human population started to grow faster than ever before. Habitats have been extensively lost, followed by severe consequences on biodiversity. Bats are one order that has suffered from population declines caused by habitat loss - either from complete loss, or lost accessibility caused by fragmentation. The forest living bat species are particularly affected by forest fragmentation because they avoid crossing open ground. This may be because of predator avoidance, which also seems to be the reason they avoid light. This study examines whether connectivity facilitates movement between habitats in the landscape for the forest dwelling Myotis species. Bat activity was recorded with automatic ultrasound detectors in habitat elements with different levels of isolation (isolated islands, connected islands, corridors and continuous forest as controls) in Tierp, Sweden, during the month of July 2021. In general, the occurrence of Myotis on islands was not different from mainland, and there was no correlation between occurrence on isolated islands and size, distance to mainland, or distance to nearest habitat. However, the occurrence on isolated islands was related to the date of observation. This could be explained by the light summer nights of northern Europe in June and beginning of July. When observations later in July were excluded, occurrence on isolated islands was related to island size, thus when nights became darker bats dispersed to more isolated habitats. Light seems to enhance the isolation effect and be a bigger impediment for habitat use than fragmentation alone.