This video says about itself:
13 September 2014
A pond bat (Myotis dasycneme) is hunting over a canal in midsummer. Fast flight low over the water surface. Wet sounds in heterodyne tuned at 35 kHz. Recording with a Nite Site Spotter and a Pettersson ultrasound detector.
Today, wildlife warden Marike Vissers from the Veluwe region in the Netherlands writes about a discovery in a restored old well in Hoog Buurlo village.
This well turns out to be second most important place in Gelderland province for hibernating pond bats. Pond bats are rare in the Netherlands.