1. Overview
19
4.4.2 Social Sounds: Signature Whistles
Dolphins are known to develop individually distinctive whistles that have
been called signature whistles, a term introduced by Caldwell and Caldwell
(1965). Caldwell et al. (1990) found that signature whistles made up about
94% of each individual's whistles. Most of the whistles were recorded while
the individual dolphins were isolated. The signature whistles were distinctive among individuals and each individual produced a stereotyped signature whistle that was stable over many years. More on the subject will be
presented by Tyack and Clark (Chapter 4).
Signature whistles have also been observed in wild bottlenose dolphins.
Bottlenose dolphin in Sarasota Bay, Florida, have been involved in an
annual capture-release program for more than 25 years, in which animals
are captured, measured, aged, sexed, sampled, and marked, and their whistles recorded by means of a hydrophone in a suction cup before the animals
are released (Wells 1991). Sayigh et al. (1990) and Sayigh (1992) found signature whistles in the "Sarasota" dolphins that were similar to the captiveanimal work of Caldwell et al. (1990). Smolker et al. (1993) found signature
whistles in a population of wild truncatus off Peron Peninsula in western
Australia. They found that signature whistles occurred primarily when
mother-infant pairs were separated, and the whistles were repetitive and
were generally concentrated toward the later stages of the separation
involving the process of reunion. When the separation was greater than
100m, the emitted sounds of the infants were always signature whistles. As
the range decreased the percent of whistle events also decreased and rarely
occurred when infants were together with their mothers. Highly individualized signature whistles may be useful in a fission-fusion society in which
individuals join and leave temporary groups in a fluid manner, yet maintain
long-term association with particular individuals (Smolker et al. 1993).
Herzing (Chapter 5) has spent more than 10 seasons studying a population
of Atlantic spotted dolphins (S. frontalis) along the sand banks and adjacent deep waters off Grand Bahama Island in the Bahamas. Signature whistles were observed in three behavioral contexts: (1) Mothers produced their
own signature whistles after calves departed from them. After the mother
whistled, the calves rejoined her. (2) Older male and female spotted dolphins in an association with younger dolphins produced their own signature whistles prior to the retrieval of younger dolphins. (3) Female and male
spotted dolphins were observed repetitively broadcasting their own signature whistle during attempted courtship and mating activity. S. frontalis
infants produce signature whistles that closely match the signature whistle
of their mother and may use them for periods greater than 10 years
(Herzing 1996) whereas bottlenose dolphin calves appear to develop
signature whistles that are quite different from those of their parents
(Caldwell and Caldwell 1979; Sayigh 1992).
19
4.4.2 Social Sounds: Signature Whistles
Dolphins are known to develop individually distinctive whistles that have
been called signature whistles, a term introduced by Caldwell and Caldwell
(1965). Caldwell et al. (1990) found that signature whistles made up about
94% of each individual's whistles. Most of the whistles were recorded while
the individual dolphins were isolated. The signature whistles were distinctive among individuals and each individual produced a stereotyped signature whistle that was stable over many years. More on the subject will be
presented by Tyack and Clark (Chapter 4).
Signature whistles have also been observed in wild bottlenose dolphins.
Bottlenose dolphin in Sarasota Bay, Florida, have been involved in an
annual capture-release program for more than 25 years, in which animals
are captured, measured, aged, sexed, sampled, and marked, and their whistles recorded by means of a hydrophone in a suction cup before the animals
are released (Wells 1991). Sayigh et al. (1990) and Sayigh (1992) found signature whistles in the "Sarasota" dolphins that were similar to the captiveanimal work of Caldwell et al. (1990). Smolker et al. (1993) found signature
whistles in a population of wild truncatus off Peron Peninsula in western
Australia. They found that signature whistles occurred primarily when
mother-infant pairs were separated, and the whistles were repetitive and
were generally concentrated toward the later stages of the separation
involving the process of reunion. When the separation was greater than
100m, the emitted sounds of the infants were always signature whistles. As
the range decreased the percent of whistle events also decreased and rarely
occurred when infants were together with their mothers. Highly individualized signature whistles may be useful in a fission-fusion society in which
individuals join and leave temporary groups in a fluid manner, yet maintain
long-term association with particular individuals (Smolker et al. 1993).
Herzing (Chapter 5) has spent more than 10 seasons studying a population
of Atlantic spotted dolphins (S. frontalis) along the sand banks and adjacent deep waters off Grand Bahama Island in the Bahamas. Signature whistles were observed in three behavioral contexts: (1) Mothers produced their
own signature whistles after calves departed from them. After the mother
whistled, the calves rejoined her. (2) Older male and female spotted dolphins in an association with younger dolphins produced their own signature whistles prior to the retrieval of younger dolphins. (3) Female and male
spotted dolphins were observed repetitively broadcasting their own signature whistle during attempted courtship and mating activity. S. frontalis
infants produce signature whistles that closely match the signature whistle
of their mother and may use them for periods greater than 10 years
(Herzing 1996) whereas bottlenose dolphin calves appear to develop
signature whistles that are quite different from those of their parents
(Caldwell and Caldwell 1979; Sayigh 1992).