we are pleased to announce the publication of our recent
paper:
Kriesell
HJ, Elwen SH, Nastasi A, Gridley T (2014): Identification
and Characteristics of Signature Whistles in Wild
Bottlenose Dolphins (Tursiops truncatus) from Namibia.
PLoS ONE 9(9): e106317. doi:10.1371/journal.pone.0106317
Abstract: A signature whistle type is a
learned, individually distinctive whistle type in a
dolphin's acoustic repertoire that broadcasts the identity
of the whistle owner. The acquisition and use of signature
whistles indicates complex cognitive functioning that
requires wider investigation in wild dolphin populations.
Here we identify signature whistle types from a population
of approximately 100 wild common bottlenose dolphins (Tursiops
truncatus)
inhabiting Walvis Bay, and describe signature whistle
occurrence, acoustic parameters and temporal production. A
catalogue of 43 repeatedly emitted whistle types (REWTs)
was generated by analysing 79 hrs of acoustic recordings.
From this, 28 signature whistle types were identified
using a method based on the temporal patterns in whistle
sequences. A visual classification task conducted by 5
naïve judges showed high levels of agreement in
classification of whistles (Fleiss-Kappa statistic, κ =
0.848,Z=
55.3,P<0.001)
and supported our categorisation. Signature whistle
structure remained stable over time and location, with
most types (82%) recorded in 2 or more years, and 4
identified at Walvis Bay and a second field site
approximately 450 km away. Whistle acoustic parameters
were consistent with those of signature whistles
documented in Sarasota Bay (Florida, USA). We provide
evidence of possible two-voice signature whistle
production by a common bottlenose dolphin. Although
signature whistle types have potential use as a marker for
studying individual habitat use, we only identified
approximately 28% of those from the Walvis Bay population,
despite considerable recording effort. We found that
signature whistle type diversity was higher in larger
dolphin groups and groups with calves present. This is the
first study describing signature whistles in a wild
free-rangingT. truncatuspopulation
inhabiting African waters and it provides a baseline on
which more in depth behavioural studies can be based.