Rivers as possible landmarks in the orientation flight of Miniopterus schreibersii

This study examines the initial orientation of Miniopterus schreibersii (Kuhl, 1817) when released from their roosts and analyses the significance of rivers as landmarks in bat navigation. Two orientation tests were carried out in which the bats were released in areas familiar to them and two further tests were carried out in unfamiliar areas. In both types of areas one of the tests was performed close to a river and the other away from a river. Initial orientation capability of M. schreibersii was verified in all tests except in unfamiliar area away from a river. The test performed in unfamiliar area with river showed higher mean angular deviation and lower directionality than the two tests performed in familiar areas. Most of the bats released near a river both in a familiar area and in an unfamiliar one turned towards the watercourse. The results obtained in these two last tests proved that the bats tended to turn towards the river. There were no significant differences between the directions taken by males and females in each of the four tests. Rivers seem to be landmarks in the navigation of the species and also paths to be followed in migratory flights.