Ecological Constraints for Sound Communication: From Grasshoppers to Elephants 63
A
100
200
Time [ms]
B 40
2
t:
Q)
&30
......
0
~20
.J:l
E
::J
ZlQ
0 0
100
200
>250
Heigh t [em]
c
10m -1 :l\ :11 1, !Hl ll ll~ll ~~I :If I
.... , .......... ,
2m
Fig. 1 A-C. A The calling song of the bog katydid Metrioptera sphagnorum is composed
of an audio mode with frequencies around 17 kHz, and an ultrasonic mode at about 34 kHz,
alternating continuously. B Males establish broadcast positions on small spruce trees within
the bog, at an average height (black bars) about 50 em below the maximum available
height (top of the trees; hatched bars). C Discharge of the omega-neuron of a receiver at
distances of 2 and I 0 m, in response to a calling male. The calling song of a male was
recorded with an ultrasonic detector (see lower traces), indicating the presence of the
ultrasonic mode. The audio mode is always present in the pauses in between. Note that at
1 0 m the neuron only responds to the audio mode. (Romer and Morris, unpubl.)
A recent experimental demonstration for the grasshopper Chorthippus biguttulus
was given by Gilbert and Elsner (2000) using the afferent activity of tympanal
receptor fibres as a biological microphone in the field. They could show that in
dense vegetation, but not on gravel or in sparse vegetation, binaural directional
cues are strongly affected, a fmding that is consistent with the observation that this
A
100
200
Time [ms]
B 40
2
t:
Q)
&30
......
0
~20
.J:l
E
::J
ZlQ
0 0
100
200
>250
Heigh t [em]
c
10m -1 :l\ :11 1, !Hl ll ll~ll ~~I :If I
.... , .......... ,
2m
Fig. 1 A-C. A The calling song of the bog katydid Metrioptera sphagnorum is composed
of an audio mode with frequencies around 17 kHz, and an ultrasonic mode at about 34 kHz,
alternating continuously. B Males establish broadcast positions on small spruce trees within
the bog, at an average height (black bars) about 50 em below the maximum available
height (top of the trees; hatched bars). C Discharge of the omega-neuron of a receiver at
distances of 2 and I 0 m, in response to a calling male. The calling song of a male was
recorded with an ultrasonic detector (see lower traces), indicating the presence of the
ultrasonic mode. The audio mode is always present in the pauses in between. Note that at
1 0 m the neuron only responds to the audio mode. (Romer and Morris, unpubl.)
A recent experimental demonstration for the grasshopper Chorthippus biguttulus
was given by Gilbert and Elsner (2000) using the afferent activity of tympanal
receptor fibres as a biological microphone in the field. They could show that in
dense vegetation, but not on gravel or in sparse vegetation, binaural directional
cues are strongly affected, a fmding that is consistent with the observation that this