238
D.L. Herzing
to the species and, perhaps, the behavior of the predator. In most cases,
dolphins are silent in the presence of sharks, at least within the human
audible range. With large groups of mixed-age classes, dolphins sink to the
bottom, closely gather, and swim in the opposite direction. With dyads or
small subgroups of dolphins, they may lay motionless on the bottom as the
shark passes by. In one instance, a mother who had recently been wounded
by a shark and apparently was in a state of hypervigilance with her calf,
began using an excitement vocalization in murky water when a nurse shark
(Ginglymostoma cirratum), a harmless species, came into view. In other
instances, S. frontalis have been observed swimming in the company of
large tiger sharks. During these times the dolphins may be discriminating
between hunting and nonhunting predators by monitoring the predator
in their presence rather than fleeing, indicating that subtle cues may be
perceived about the intention of the predator.
3.3 Vocalizations Associated with Pursuit,
Herding, and Discipline
During the pursuit and herding of conspecifics the predominant vocalization
produced is the "buzz" or "genital buzz." This vocalization is a lowfrequency, high-repetition-rate echolocation train that is directed toward the
genital or midsection of a conspecific, often by a male to a receptive female
during courtship behavior. This vocalization ranges from 1.2 to 2.5 kHz, with
durations up to 20s and repetition rates of eight clicks per second up to
2,000 clicks per second.
A similar type of buzz is used when individuals are disciplining others.
When mothers are unsuccessful in retrieving their calves, they swim
inverted and buzz the genital/peduncle area of their offspring, eventually
making physical contact with their rostra. Larger groups of dolphins are
observed in tight physical contact, with their rostra pointed toward, but not
touching, another dolphin, while they buzz the genital/peduncle area of the
individual, who initially tries to swim away from the group. When physical
contact of their rostra to the individual's body is finally made, the single
dolphin becomes passive and allows itself to be pushed around by the
group. In some instances, the single dolphin is held down to the bottom,
similar to disciplinary actions between a mother and calf. This behavioral
sequence is observed both intraspecifically within and between all age
classes of S. frontalis, and interspecifically between juvenile and young adult
spotted dolphins and T. truncatus. The buzz is also used by the dolphins
when chasing sharks.
Although this genital buzz described for S. frontalis is not found in the
literature, echolocation trains termed a "buzz" have been reported in threat
situations (Lilly and Miller 1961) and during general social interactions
(Reiss 1988). The highest intensities and frequencies of echolocation clicks
D.L. Herzing
to the species and, perhaps, the behavior of the predator. In most cases,
dolphins are silent in the presence of sharks, at least within the human
audible range. With large groups of mixed-age classes, dolphins sink to the
bottom, closely gather, and swim in the opposite direction. With dyads or
small subgroups of dolphins, they may lay motionless on the bottom as the
shark passes by. In one instance, a mother who had recently been wounded
by a shark and apparently was in a state of hypervigilance with her calf,
began using an excitement vocalization in murky water when a nurse shark
(Ginglymostoma cirratum), a harmless species, came into view. In other
instances, S. frontalis have been observed swimming in the company of
large tiger sharks. During these times the dolphins may be discriminating
between hunting and nonhunting predators by monitoring the predator
in their presence rather than fleeing, indicating that subtle cues may be
perceived about the intention of the predator.
3.3 Vocalizations Associated with Pursuit,
Herding, and Discipline
During the pursuit and herding of conspecifics the predominant vocalization
produced is the "buzz" or "genital buzz." This vocalization is a lowfrequency, high-repetition-rate echolocation train that is directed toward the
genital or midsection of a conspecific, often by a male to a receptive female
during courtship behavior. This vocalization ranges from 1.2 to 2.5 kHz, with
durations up to 20s and repetition rates of eight clicks per second up to
2,000 clicks per second.
A similar type of buzz is used when individuals are disciplining others.
When mothers are unsuccessful in retrieving their calves, they swim
inverted and buzz the genital/peduncle area of their offspring, eventually
making physical contact with their rostra. Larger groups of dolphins are
observed in tight physical contact, with their rostra pointed toward, but not
touching, another dolphin, while they buzz the genital/peduncle area of the
individual, who initially tries to swim away from the group. When physical
contact of their rostra to the individual's body is finally made, the single
dolphin becomes passive and allows itself to be pushed around by the
group. In some instances, the single dolphin is held down to the bottom,
similar to disciplinary actions between a mother and calf. This behavioral
sequence is observed both intraspecifically within and between all age
classes of S. frontalis, and interspecifically between juvenile and young adult
spotted dolphins and T. truncatus. The buzz is also used by the dolphins
when chasing sharks.
Although this genital buzz described for S. frontalis is not found in the
literature, echolocation trains termed a "buzz" have been reported in threat
situations (Lilly and Miller 1961) and during general social interactions
(Reiss 1988). The highest intensities and frequencies of echolocation clicks