Response to Frequency Shifted Artificial Echoes in the Bat Rhinolophus ferrumequinum
b'In 5 roosting bats the resting frequency, that is the mean frequency\\nof the cf-portion of consecutive sounds, is kept constant with a standard deviation\\nwhich varies between 30 120 Hz in different bats and at different days. In 15 bats\\nthe emitted sounds were electronically shifted in frequency and played back as\\nartificial echoes. Upward frequency shifts were responded by a decrease of the\\nemission frequency. This frequency compensation occurred at frequency shifts\\nof up to 4400 Hz in all bats and up to 6000 ttz in a few bats. The frequency decrease\\nin different bats over the whole compensation range was 50-300 tIz smaller than\\nthe frequency shifts in the echoes. The echoes, therefore, returned at a frequency,\\ncalled the reference frequency, which was by this compensation offset higher\\nthan the resting frequency. The standard deviations of the emission frequency\\nin compensating bats were only slightly larger than in roosting bats and the same\\nin the whole compensation range. All bats started to compensate frequency shifts\\nwhen they were slightly larger than the compensation offset. Downward frequency\\nshifts were not responded by a change of the emission frequency, but the accuracy\\nwith which the emission frequency was kept decreased somewhat. From these\\nresults it is concluded that the Doppler shift compensation system of the Horseshoe\\nbats compares the echo frequency with the reference frequency and compensates\\ndeviations of upward frequency shifts.'