Signature whistle shape conveys identity information to bottlenose dolphins

Abstract

Bottlenose dolphins (Tursiops truncatus) develop individually distinctive signature whistles that they use to maintain group cohesion. Unlike the development of identification signals in most other species, signature whistle development is strongly influenced by vocal learning. This learning ability is maintained throughout life, and dolphins frequently copy each other's whistles in the wild. It has been hypothesized that signature whistles can be used as referential signals among conspecifics, because captive bottlenose dolphins can be trained to use novel, learned signals to label objects. For this labeling to occur, signature whistles would have to convey identity information independent of the caller's voice features. However, experimental proof for this hypothesis has been lacking. This study demonstrates that bottlenose dolphins extract identity information from signature whistles even after all voice features have been removed from the signal. Thus, dolphins are the only animals other than humans that have been shown to transmit identity information independent of the caller's voice or location.animal communication ͉ individual recognition ͉ Tursiops truncatus

Dolphin social intelligence: complex alliance relationships in bottlenose dolphins and a consideration of selective environments for extreme brain size evolution in mammals

“…Whistles come in discrete research-friendly packages which can be recorded and played back to dolphins with relative ease. In short, we have learned that a prominent type of whistle produced by bottlenose dolphins is their 'signature' whistle (Caldwell & Caldwell 1965;Caldwell et al 1990), a learned vocalization (Tyack 1997;Miksis et al 2002) that yields information about identity (Sayigh et al 1999) based not on voicing but frequency contour (Janik et al 2006), and that whistles are used as a contact call when animals are out of visual range (Smolker et al 1993, Janik & Slater 1998.…”

“…The possibilities get very interesting when the dolphins' imitative abilities are juxtaposed with the recent finding that it is the contour of the signature whistle that conveys identity (Janik et al 2006). These two ingredients could form the basis of a system that allows dolphins to communicate about others in their absence, especially when combined with other whistle attributes or pulsed sounds that communicate affect (that pulsed sounds play an important role in communicating affect seems clear; beyond that our understanding of this rich vocal output is minimal, but see Herman & Tavolga 1980, pp.…”

Changes in bottlenose dolphin whistle parameters related to vessel presence, surface behaviour and group composition

“…Each bottlenose dolphin uses an individually distinctive signature whistle which is acquired through vocal production learning in the first year of life (Caldwell & Caldwell, 1979;Janik & Slater, 1997). Around 50% of all whistles recorded from free-ranging bottlenose dolphins are signature whistles (Cook, Sayigh, Blum, & Wells, 2004) which are used to convey identity information (Janik, Sayigh, & Wells, 2006), facilitate group contact (Janik & Slater, 1998;Quick & Janik, 2012) and address conspecifics . The function of other, nonsignature whistles in the dolphin's repertoire is less well understood.…”

Cross-modal individual recognition in domestic horses ( Equus caballus )

“…A number of species have been shown to make very finegrained discriminations between different individuals (6)(7)(8). For example, in the habituation-dishabituation paradigm, subjects that are habituated to the call of one known individual will dishabituate when presented with the calls of a different known individual.…”