244
D.L. Herzing
Although echolocation has traditionally been thought to be used in
orientation and navigation, dolphins produce a type of echo "buzzing" while
playing with objects and conspecifics. S. frontalis often echolocate intensely
while playing with relatively inanimate objects such as sea grass and sea
cucumbers during conditions of excellent underwater visibility. Since such
immobile objects negate the need for targeting practice, such buzzing could
serve as an acoustic point or tactile stimulator rather than a tool for targeting or debilitating the object. When buzzing conspecifics, certain areas
of the body are buzzed, inferring some possible rules or etiquette about the
nature of social echolocation.
The relative positioning of conspecifics could facilitate the reception of
ensonification information. For example, S. frontalis calves position themselves below the mother during foraging, traveling, and socializing, potentially maximizing exposure to the use of echolocation for both hunting and
socializing. During male coalition behavior, male S. frontalis group within
body contact, facilitating not only a potential tactile requirement for reassurance or the aquatic version of piloerection, but perhaps maximizing the
group's ability to share and perceive reflected signals from the object of
their sonic attention. Similar physical behavior has been observed in S.
attenuata in tuna nets (Pryor and Kang-Shallenberger 1991). Close proximity and angle are critical in determining the eavesdropping abilities of
T. truncatus (Xitco and Roitblat 1996) and dolphin formations and relative
positions may facilitate aspects of hearing.
4. Sensory Envelopes and Potential Information
The total sensory envelope of potential information available for dolphins
may include vocal as well as nonvocal signals (e.g., visual, tactile, kinesthetic,
and chemoreceptive). Some of the obvious needs for hearing and deciphering information include:
1. environmental navigation and orientation
2. predator detection and alarm
3. coordinating activity
4. signals for group cohesion
5. stealth options
6. communication (short distance, long distance, and multimodal)
7. social negotiation and monitoring
Salient information is in the eye of the beholder, and relative salience
will vary as a function of signal change in the environment or the social
envelope (Fig. 5.2). Potential dolphin sound sets include:
1. environmental-waves, current, seismic activity, rain, boats (see review
in Richardson et at. 1995)
D.L. Herzing
Although echolocation has traditionally been thought to be used in
orientation and navigation, dolphins produce a type of echo "buzzing" while
playing with objects and conspecifics. S. frontalis often echolocate intensely
while playing with relatively inanimate objects such as sea grass and sea
cucumbers during conditions of excellent underwater visibility. Since such
immobile objects negate the need for targeting practice, such buzzing could
serve as an acoustic point or tactile stimulator rather than a tool for targeting or debilitating the object. When buzzing conspecifics, certain areas
of the body are buzzed, inferring some possible rules or etiquette about the
nature of social echolocation.
The relative positioning of conspecifics could facilitate the reception of
ensonification information. For example, S. frontalis calves position themselves below the mother during foraging, traveling, and socializing, potentially maximizing exposure to the use of echolocation for both hunting and
socializing. During male coalition behavior, male S. frontalis group within
body contact, facilitating not only a potential tactile requirement for reassurance or the aquatic version of piloerection, but perhaps maximizing the
group's ability to share and perceive reflected signals from the object of
their sonic attention. Similar physical behavior has been observed in S.
attenuata in tuna nets (Pryor and Kang-Shallenberger 1991). Close proximity and angle are critical in determining the eavesdropping abilities of
T. truncatus (Xitco and Roitblat 1996) and dolphin formations and relative
positions may facilitate aspects of hearing.
4. Sensory Envelopes and Potential Information
The total sensory envelope of potential information available for dolphins
may include vocal as well as nonvocal signals (e.g., visual, tactile, kinesthetic,
and chemoreceptive). Some of the obvious needs for hearing and deciphering information include:
1. environmental navigation and orientation
2. predator detection and alarm
3. coordinating activity
4. signals for group cohesion
5. stealth options
6. communication (short distance, long distance, and multimodal)
7. social negotiation and monitoring
Salient information is in the eye of the beholder, and relative salience
will vary as a function of signal change in the environment or the social
envelope (Fig. 5.2). Potential dolphin sound sets include:
1. environmental-waves, current, seismic activity, rain, boats (see review
in Richardson et at. 1995)