5. Acoustics and Social Behavior
259
high-frequency information available to social species greatly hinders us
from observing the full spectrum of information. With the development
of high-speed digitizing equipment and its application in the field, our
abilities to document the full acoustic repertoire of signals should increase.
7.1.6 The Directionality of Sound and Its Use
Determining the directionality of social sounds (burst-pulsed and whistles)
as well as the directionality and use of dolphin echolocation as a potential
"point" for conspecifics would be useful. In addition, the angle and proximity required to successfully eavesdrop on returning echoes in the wild
would greatly illuminate signal use.
7.2 Physiological Correlates and Arousal
Levels of Sound
McConnell (1990) reported in a study of interspecific acoustic communication that the most important variations along acoustic continuums were (1)
the pulsed versus continuous nature of sounds, and (2) the slope of frequency modulation within the signal. She further speculated that different
acoustic structures have different physiological effects on the internal
arousal level of the receiver. This type of response is suggested from evidence from nonhuman primates (Struhsaker 1967; Cleveland and Snowdon
1982), avian repertoires (Marler 1982), and bats (Gould 1983) and needs to
be explored in delphinids.
7.3 Graded or Discrete Signals, Signal Relations and
Prosodic Aspects of Sound
Morton (1977) devised a set of "structural and motivational" rules, based
on the harshness and the frequency of the sound, for the calls of a variety
of mammals and birds. This matrix supports the continuous and graded
nature of many signals in animal communication in which prosodic features
of sound, including rhythm, silence, and intensity, communicate information. Gish (1979) analyzed the temporal relationship of sounds between two
T. truncatus and found evidence for a rhythm or cadence where the duration of the last vocalization of one dolphin was highly correlated with the
interval before the second dolphin's vocalization period and the duration
of the first signal.
These frameworks suggest that analyzing discrete and graded multimodal
signals, the rhythm and sequence of signals, and social elements that form
a context for the animal in an environment playa crucial role in the interpretation of communication systems of many animals, including delphinids.
The universal aspects of the evolution of communication signals may also
be potentially elucidated by this area of inquiry.
259
high-frequency information available to social species greatly hinders us
from observing the full spectrum of information. With the development
of high-speed digitizing equipment and its application in the field, our
abilities to document the full acoustic repertoire of signals should increase.
7.1.6 The Directionality of Sound and Its Use
Determining the directionality of social sounds (burst-pulsed and whistles)
as well as the directionality and use of dolphin echolocation as a potential
"point" for conspecifics would be useful. In addition, the angle and proximity required to successfully eavesdrop on returning echoes in the wild
would greatly illuminate signal use.
7.2 Physiological Correlates and Arousal
Levels of Sound
McConnell (1990) reported in a study of interspecific acoustic communication that the most important variations along acoustic continuums were (1)
the pulsed versus continuous nature of sounds, and (2) the slope of frequency modulation within the signal. She further speculated that different
acoustic structures have different physiological effects on the internal
arousal level of the receiver. This type of response is suggested from evidence from nonhuman primates (Struhsaker 1967; Cleveland and Snowdon
1982), avian repertoires (Marler 1982), and bats (Gould 1983) and needs to
be explored in delphinids.
7.3 Graded or Discrete Signals, Signal Relations and
Prosodic Aspects of Sound
Morton (1977) devised a set of "structural and motivational" rules, based
on the harshness and the frequency of the sound, for the calls of a variety
of mammals and birds. This matrix supports the continuous and graded
nature of many signals in animal communication in which prosodic features
of sound, including rhythm, silence, and intensity, communicate information. Gish (1979) analyzed the temporal relationship of sounds between two
T. truncatus and found evidence for a rhythm or cadence where the duration of the last vocalization of one dolphin was highly correlated with the
interval before the second dolphin's vocalization period and the duration
of the first signal.
These frameworks suggest that analyzing discrete and graded multimodal
signals, the rhythm and sequence of signals, and social elements that form
a context for the animal in an environment playa crucial role in the interpretation of communication systems of many animals, including delphinids.
The universal aspects of the evolution of communication signals may also
be potentially elucidated by this area of inquiry.