Whistle stability and variation in captive bottlenose dolphins (Tursiops truncatus) recorded in isolation and social contexts

Lopes, Patrícia Alexandra Rachinas; Luís, Ana Rita; Borges, Ana Sofia; Neto, Márcia P.; Santos, Manuel Eduardo dos

http://hdl.handle.net/10400.12/5447

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Authors

Lopes, Patrícia Alexandra Rachinas

Luís, Ana Rita

Borges, Ana Sofia

Neto, Márcia P.

Santos, Manuel Eduardo dos

Abstract(s)

Common bottlenose dolphins (Tursiops trunca-tus) produce a range of underwater vocalizations, both pulsed (echolocation clicks and burst-pulses) and nonpulsed (whistles). Whistles may be emit-ted in stereotyped (signature) or variant patterns, and their production might be affected by sex, age, environmental, and social contexts. This study examined, non-intrusively, the whistle emissions of six captive bottlenose dolphins at Zoomarine in Algarve, Portugal, in two separate time sets and three different contexts: two of the animals in isolation in 2008, and all six in 2012, both seg-regated from their group and in social context. From a total of 1,681 whistles, 1,249 were ana-lyzed from 32 samples in different contexts: seven samples in isolation in 2008, 18 in segregation in 2012, and seven in social context. Through visual inspection of spectrograms, whistles were classi-fied into 12 different contour categories. Only one category was found in both time sets and could be considered a signature whistle by SIGID criteria (Janik et al., 2013). This contour was associated with the same animal in 2008 and 2012. Whistle emission rates were 7.8 times higher in isolation as compared with social context, and significant differences were also found in the end and maxi-mum frequencies as well as number of inflections and loops. Multiloop whistles were more common in isolation than in social contexts. The variant (nonstereotyped) contours dominated the whistle production in segregated contexts (but not by iso-lated animals) as well as in social contexts. This study highlights the importance of examining the nonstereotyped portion of the bottlenose dolphin’s whistle repertoire in different contexts as signa-ture whistle production may not be a constant or universal phenomenon.