> (3) Can someone with bats ad some like species to the list?
Rob,
I'm into UK bat species as I do bat conservation work here, but I
can't give you a list of American species except generally its the
vesper bats (microbats) which are insectiverous and echolocate and
typical frequencies range from 20 kHz TO 60 khZ and higher.
The nature of the high voltage discharge sound is that it will pulse
at twice or six times (3 phase) line frequency and could easily mask
echolocation echoes from insects being hunted for food. However, you
have to be careful here as ultrasound is absorbed by the at the rate
of about 1 dB per metre at 50KHz. This gives many bats an echolocation
limit of around 15 to 20 metres. Lower frequencies around 30 KHz
travel further but they still get absorbed at about 0.7 dB per metre.
The best way to get ultrasound recordings is to find a bat enthusiast
with a "time expansion" bat detector. This records a few seconds and
plays it back at a reduced frequency 1/10 or 1/16 so they can be
analysed using audio devices like a laptop.
I would have thought that the greatest hazard would be if the cables
were in a migration route or feeding corridor. I don't have figures to
hand but the avian mortality rate can be significant.
David
David Brinicombe
North Devon, UK
Cogito cogito ergo cogito sum - Ambrose Bierce
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