[MARMAM] New Paper: Changes in bottlenose dolphin whistle parameters related to vessel presence, surface behaviour and group composition

Tess Gridley - Namibian Dolphin Project nam.dolphin.project at gmail.com
Mon Jul 4 11:57:24 PDT 2016

Dear colleagues,

The Namibian Dolphin Project are pleased to announce the publication of the
following paper in Animal Behaviour:

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


Cetacean watching from tour boats has increased in recent years and
has been promoted as an ethically viable alternative to cetacean
viewing in captive facilities or directed take. However, short- and
long-term impacts of this industry on the behaviour and energetic
expenditure of cetaceans have been documented. Although multiple
studies have investigated the acoustic response of dolphins to marine
tourism, there are several covariates that could also explain some of
these results and should be considered simultaneously. Here, we
investigated whether common bottlenose dolphins,*Tursiops truncatus*,
inhabiting Walvis Bay, Namibia vary their whistle parameters in
relation to boat presence, surface behaviour and/or group composition.
We detected an upward shift of up to 1.99 kHz in several whistle
frequency parameters when dolphins were in the presence of one or more
tour boats and the research vessel. No changes were demonstrated in
the frequency range, number of inflection points or duration of
whistles. A similar, although less pronounced difference was observed
in response to engine noise generated by the research vessel when
idling, suggesting that noise alone plays an important role in driving
this shift in whistle frequency. Additionally, a strong effect of
surface behaviour was observed, with the greatest difference in
whistle parameters detected between resting and other behavioural
states that are associated with higher degrees of emotional arousal.
Group composition also contributed to the variation observed, with the
impact of boats dependent on whether calves were present or not.
Overall these results demonstrate high natural variation in the
frequency parameters of whistles utilized by dolphins over varying
behavioural states and group composition. Anthropogenic impact in the
form of marine tour boats can influence the vocalization parameters of
dolphins and such changes could have a long-term impact if they reduce
the communication range of whistles or increase energy expenditure.

This is available to download from the following link until the 27th July

Or request a pdf copy from: nam.dolphin.project at gmail.com or

julia.heiler at web.de
Kind regards,
NDP Team


Tess Gridley PhD

Namibian Dolphin Project & Sea Search

Centre for Statistics in Ecology,
Environment and Conservation,
Department of Statistical Sciences,
University of Cape Town, South Africa

Tel: 021 788 1206
Cell: 0794292702
Skype: tess.gridley
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