Dolphin whistles as frequency modulated carriers for amplitude modulation encoded information
Acoustic encodings for identity in the signature vocalizations of an individual should be perceived as similar to each other while distinct from those of other individuals (Falls, 1982; Shapiro, 2010). In contrast, different non-identity information encodings (e.g., predator type, Seyfarth et al., 1980) from the same individual should be perceptually distinct, but similar across group members. Given this conflict, selection pressures favoring the simultaneous incorporation of identity and non-identity information in a single vocalization type may stimulate the evolution of vocal forms in which these different types of information are encoded exclusively or partly in minimally interacting acoustic structures.
Experiments provide considerable evidence that identity is encoded in the FM contour of bottlenose dolphin signature whistles (Janik et al., 2006). These same experiments demonstrate that alterations in AM patterns do not impair signature whistles’ identity encoding function. Therefore, signature and non-signature whistles may have the capacity to function as FM carriers of AM patterns for encoding non-identity information, perhaps in conjunction with some minimal, concurrent FM variation. With AM having minimal influence on the FM contour, whistles would retain critical signature functionality such as group cohesion (Janik & Slater, 1998). Papers in preparation, which include this model developed in 2011, with tools to analyze vocalizations, and a 2018 dolphin communication experiment.
Attachment: References_Dolphin_whistles_as_frequency_modulated_carriers_for_amplitude_modulation_encoded_information.pdf (194 KB)
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