For example, Nyctalus noctula hunting high in
open air, using frequency-modulated, quasi-constantfrequency
(FM-QCF) pulses, will be detected at a
greater range than Eptesicus serotinus, which also hunts in
the open, but closer to clutter using somewhat shorter
FM-QCF pulses. In general, bats using QCF or shallow
FM calls are louder then those using strictly FM calls.
Clutter also influences the calls used by bats. Bats hunting
in clutter or hunting closer to vegetation will use
steeper pulses, which are detected over a shorter range.
Higher frequencies in the more intense QCF part of the
pulse also have a lower detection range. The calls of Pipistrellus
pygmaeus (QCF 55 kHz) have a similar amplitude
as those of P. pipistrellus (QCF 45 kHz; Holderied 2001),
but are detected over shorter distances. These factors
result in species- and habitat-specific differences in the
sampling areas of detectors and affect the probability of
detecting different species in different habitatshe