ultrasound detectors

["Peter Cusack" peter911403]

hi

on a recent trip to India i met a biologist studying Loris monkeys. 
she believes that they communicate ultrasonically, although it's not 
proven.

can members of the list recommend available devices that could be 
used to detect such communications. she suspects that the frequencies 
would be relatively low in the ultrasound range, below that of many 
bats and also that the signals may not be that strong.

any advise would be very helpful.

many thanks

peter