Use of signature whistles during separations and reunions by wild bottlenose dolphin mothers and infants

Abstract

We examine the contexts and patterns of "signature" whistle production by wild bottlenose dolphin mother-infant pairs (Tursiops spp.) to gain insight into the functional significance of whistles. Results are based on focal observations and simultaneous recordings of underwater vocalizations. Whistles occur primarily when mother-infant pairs are separated, and the probability of whistles increases with distance of separation. The timing of whistles during separations varies, but whistles tend to be produced in repetitive series and are generally concentrated toward the later stages of the separation, i.e., during the process of reunion. Although we focused on infants, mothers do not appear to whistle during separations as frequently as infants. Infant whistles may function to facilitate reunions by conveying information to the mother concerning the infant's motivation to reunite and/or its location. Infant whistles could induce a cooperative response from the mother including approach, slowing to allow the infant to catch up or whistling. Highly individualized signature whistles may be particularly useful in a fission-fusion society in which individuals (mothers and infants as well as adults) join and leave temporary parties in a fluid manner, yet maintain consistent, long-term associations with particular individuals.

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

“…However, other studies focusing on signature whistles have found that whistle duration (and number of inflection points) increases with age (Caldwell & Caldwell, 1979;Caldwell et al, 1990). The differences in duration observed could therefore also be explained by increased rates of signature whistle production by adult animals, possibly mothers during separations from their offspring in the mother-calf groups (Mello & Amundin, 2005;Sayigh et al, 1990;Smolker, Mann, & Smuts, 1993). As in other studies (Hawkins & Gartside, 2010), calf presence in this population is highly correlated with group size, with calves being present in larger groups (Kriesell et al, 2014).…”

Variation in the emission rate of sounds in a captive group of false killer whales Pseudorca crassidens during feedings: possible food anticipatory vocal activity?

“…This hypothesis could be supported by the overall increase of the rates of all sound classes during the pre-feeding intervals. Higher rates of whistles and burst pulses have been reported in dolphins during diff erent behavioral contexts characterized by high arousal levels (Busnel and Dziedzic, 1966;Smolker et al, 1993;Norris et al, 1994;Herzing, 1996;Acevedo-Gutiérrez and Stienessen, 2004;dos Santos et al, 2005). Moreover, clicks are normally used by dolphins during inquisitive behaviors (Supin et al, 2004(Supin et al, , 2005Nachtigall and Supin, 2008).…”

“…For example, modifi cations of the rate of the whistles have been observed in diff erent dolphin species during distinct behavioral contexts such as excitement and stress in Hawaiian spinner dolphins ( Stenella longirostris : Norris et al, 1994), during bow riding and feeding in common dolphins ( Delphinus delphis : Busnel and Dziedzic, 1966), feeding in pilot whales ( Globicephala sp. : Dreher and Evans, 1964), feeding, cooperative behavior, socialising (AcevedoGutiérrez and Stienessen, 2004;dos Santos et al, 2005), and mother/calf reunions in bottlenose dolphins (Smolker et al, 1993). The degree of exposure to human activities and interactions have also been found infl uential on the rate of the acoustic emissions of dolphins (Smolker et al, 1993;Scarpaci et al, 2000;Mann and Kemps, 2003;Morisaka et al, 2005;Hawkins and Gartside, 2009a, b ).…”

“…: Dreher and Evans, 1964), feeding, cooperative behavior, socialising (AcevedoGutiérrez and Stienessen, 2004;dos Santos et al, 2005), and mother/calf reunions in bottlenose dolphins (Smolker et al, 1993). The degree of exposure to human activities and interactions have also been found infl uential on the rate of the acoustic emissions of dolphins (Smolker et al, 1993;Scarpaci et al, 2000;Mann and Kemps, 2003;Morisaka et al, 2005;Hawkins and Gartside, 2009a, b ). For example, an increase of all types of underwater sounds have been recorded in diff erent captive cetaceans (bottlenose dolphins, Tursiops truncatus : Tyack, 1986;Janik et al, 1994;Sekiguchi and Koshima, 2003;Akiyama and Ohta, 2007;Beluga whales, Delphinatuera leuca : Fish and Mowbray, 1962; Pacifi c white-sided dolphins, Lagenorhynchus obliquidens : Brickman, 2003) during activities that were special moments for the dolphins such as training, feeding sessions, or public presentations which might have increased the level of excitement of the animals (Tyack, 1986;Janik et al, 1994).…”

Vessel noise effects on delphinid communication

“…The bottlenose dolphin Tursiops sp. is an example of a cetacean that lives in fission-fusion societies (Wursig & Wursig 1977, Connor et al 2000, Connor et al 2006, where acoustic cues play an important role in mediating social structure (Janik & Slater 1998, Watwood et al 2005, predator avoidance (Deecke et al 2005), mate choice (Gerhardt & Klump 1988), mothercalf interactions (Renouf 1984, Smolker et al 1993), cooperative foraging (Janik 2000) and perhaps cultural learning or eavesdropping (Janik 2005). Sound most likely serves similar functions for the highly social short-finned pilot whale Globicephala macrorhynchus (Heimlich-Boran & Heimlich-Boran 1992, Heimlich-Boran 1993.…”