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D.L. Herzing
broadcast their signature whistles during attempted courtship and mating
activity; and (4) individual separation from the group-solitary dolphins,
apparently separated from the group, take a position on or near the bottom
and emit their signature whistle for minutes while rotating their head. It is
unclear whether the dolphins are waiting for a response from a conspecific
or broadcasting to members of their group. Recent speculations (Payne and
Webb 1971) on the function of long-distance, low-frequency-modulated
signals from large balenopterid whales for an "echo-ranging" function (by
hitting long-distance targets such as underwater seamounts) challenges
our traditional thoughts about the possible uses of frequency-modulated
vocalizations.
Whistles are thought to display relatively low directionality as longdistance social communicative signals due to their highly modulated frequency characteristics (Norris and Dohl 1980) and may broadcast individual identity and help maintain or initiate contact between individuals
(Smolker et al. 1993; Tyack 1993; Herzing 1996). This is supported by both
the stability of whistle contours over the years and kin-related identifiers
in whistles (Sayligh et al. 1990). Emotive information possibly contained in
such whistles has also been explored (Caldwell and Caldwell 1967; Reiss
1988; Herzing 1996). The use of bubble streams as identifiers of both the
individual vocalizing and as representative of the full repertoire of whistles
has been verified (McCowan and Reiss 1995). However, recent theories on
the possible continuum of clicks and whistles, and the inherent directionality of the sound production mechanism of clicks, challenges the idea that
whistles are always, if at all, omnidirectional (Murray 1997).
Other general associations between whistles and behavior include
increased whistling rate during excitement and stress in S. longirostris
(Norris et al. 1994), during bow riding and feeding in the common dolphin,
Delphinus delphis (Busnel and Dziedzic 1966), during feeding in
Globicephala sp. (Dreher and Evans 1964), during fleeing and cooperative
behavior (Evans 1966), and during mother/infant reunions in T. truncatus
(Smolker et al. 1993).
Caldwell and Caldwell (1965) first suggested, and later revised (Caldwell
et al. 1990), that repetitive whistles, termed "signature" whistles, may be
individually specific and may function as identifiers of individual dolphins.
Signature whistles have already been described for captive S. frontalis
(Caldwell et al. 1973). Recently, an expansion/replacement theory termed
"whistle repertoire" theory, which normalizes all whistles to their common
features and acknowledges the contextually appropriate social situations
for whistle use, has recently been proposed (McCowan and Reiss 1995).
Although some individual S. frontalis have a unique and predominate
distinctive whistle, new quantification and normalization techniques described above have not yet been applied to these data. But the existence
and stability of "signature" whistles, as described by Sayigh et al. (1990),
D.L. Herzing
broadcast their signature whistles during attempted courtship and mating
activity; and (4) individual separation from the group-solitary dolphins,
apparently separated from the group, take a position on or near the bottom
and emit their signature whistle for minutes while rotating their head. It is
unclear whether the dolphins are waiting for a response from a conspecific
or broadcasting to members of their group. Recent speculations (Payne and
Webb 1971) on the function of long-distance, low-frequency-modulated
signals from large balenopterid whales for an "echo-ranging" function (by
hitting long-distance targets such as underwater seamounts) challenges
our traditional thoughts about the possible uses of frequency-modulated
vocalizations.
Whistles are thought to display relatively low directionality as longdistance social communicative signals due to their highly modulated frequency characteristics (Norris and Dohl 1980) and may broadcast individual identity and help maintain or initiate contact between individuals
(Smolker et al. 1993; Tyack 1993; Herzing 1996). This is supported by both
the stability of whistle contours over the years and kin-related identifiers
in whistles (Sayligh et al. 1990). Emotive information possibly contained in
such whistles has also been explored (Caldwell and Caldwell 1967; Reiss
1988; Herzing 1996). The use of bubble streams as identifiers of both the
individual vocalizing and as representative of the full repertoire of whistles
has been verified (McCowan and Reiss 1995). However, recent theories on
the possible continuum of clicks and whistles, and the inherent directionality of the sound production mechanism of clicks, challenges the idea that
whistles are always, if at all, omnidirectional (Murray 1997).
Other general associations between whistles and behavior include
increased whistling rate during excitement and stress in S. longirostris
(Norris et al. 1994), during bow riding and feeding in the common dolphin,
Delphinus delphis (Busnel and Dziedzic 1966), during feeding in
Globicephala sp. (Dreher and Evans 1964), during fleeing and cooperative
behavior (Evans 1966), and during mother/infant reunions in T. truncatus
(Smolker et al. 1993).
Caldwell and Caldwell (1965) first suggested, and later revised (Caldwell
et al. 1990), that repetitive whistles, termed "signature" whistles, may be
individually specific and may function as identifiers of individual dolphins.
Signature whistles have already been described for captive S. frontalis
(Caldwell et al. 1973). Recently, an expansion/replacement theory termed
"whistle repertoire" theory, which normalizes all whistles to their common
features and acknowledges the contextually appropriate social situations
for whistle use, has recently been proposed (McCowan and Reiss 1995).
Although some individual S. frontalis have a unique and predominate
distinctive whistle, new quantification and normalization techniques described above have not yet been applied to these data. But the existence
and stability of "signature" whistles, as described by Sayigh et al. (1990),