TROUBLED WATERS - Whale and Dolphin Conservation Society
TROUBLED WATERS - Whale and Dolphin Conservation Society
TROUBLED WATERS - Whale and Dolphin Conservation Society
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
22<br />
A REVIEW OF THE WELFARE IMPLICATIONS OF MODERN WHALING ACTIVITIES<br />
Communication in great whales<br />
The most elaborate <strong>and</strong> probably best-studied form of cetacean communication in the great whales<br />
is the song of the humpback whale. Although other baleen whales also produce complex songs,<br />
notably the bowhead <strong>and</strong> right whales (Eubalaena spp.) (Clark 1990), the vocalisations of the<br />
humpback whale have received the most scientific, <strong>and</strong> public, attention. To date, the song of the<br />
humpback whale is the most complicated animal song studied <strong>and</strong> is believed to have a role in<br />
competition between males, or in determining mate selection (Tyack 1999). Each humpback whale<br />
population has its own specific song; at the beginning of the breeding season all humpback whales<br />
in a population sing approximately the same song. As the breeding season progresses the songs of<br />
each population change in structure (Payne et al. 1983). At the end of the breeding season males<br />
stop singing until the following mating season <strong>and</strong> when they resume singing, their song has the<br />
same structure as at the end of the previous breeding season (Payne et al. 1983), i.e. the song has<br />
been ‘memorised’ over the intervening period.<br />
As the song evolves through the season it is apparent that each whale is actively learning <strong>and</strong><br />
incorporating new aspects of the song structure as they are introduced. Although it is at present<br />
impossible to assess whether these changes in the song structure are due to ‘inventiveness’ by the<br />
whales, this is a possibility. Certainly the way in which the songs are learnt shows an ability to learn<br />
<strong>and</strong> memorize complex behaviours, <strong>and</strong> throughout over 30 years of recording these songs they have<br />
been shown not to revert to, or repeat, old songs, which suggests that the whales can mentally ‘keep<br />
track’ of a song’s evolution (Tyack 2002b); an impressive mental feat.<br />
Sperm whales also have sophisticated calls, in particular ‘codas’: rhythmic sets of 3-20 clicks in<br />
bursts of 0.2-2 seconds. It has been found that groups of sperm whales have group-specific codas<br />
(Weilgart <strong>and</strong> Whitehead 1997), <strong>and</strong> possibly individually distinct codas (Watkins <strong>and</strong> Schevill<br />
1977). These codas are learnt within family units <strong>and</strong> are commonly heard when members of a<br />
group rejoin after foraging. It is possible that these codas may help to strengthen social bonds, aid<br />
in-group identification or possibly act as a ‘greeting’ call. It has been suggested that verbal<br />
recognition of individuals was a prerequisite for the development of human language (Janik 2000).<br />
Sperm whales may have the building blocks for the development of a language as complex as our<br />
own.<br />
Communication has also been studied at length in certain small cetaceans, notably bottlenose<br />
dolphins <strong>and</strong> killer whales (e.g. summaries in Tyack 1999 <strong>and</strong> Dudzinski et al. 2002). Some of the<br />
most notable types of cetacean communication include the production of alarm <strong>and</strong> greeting calls<br />
(see below). In addition, it as been shown that cetaceans can communicate their individual identity<br />
(see below) which, for all intents <strong>and</strong> purposes, is effectively communicating their individual<br />
‘names’. Various researchers have proposed that the complexity of cetacean communication suggests<br />
that these animals do indeed possess language <strong>and</strong> several studies have been conducted to determine<br />
whether, in fact, cetaceans possess sufficient linguistic skills to underst<strong>and</strong> or potentially develop<br />
language (see below). Sophisticated communication mechanisms have evolved in these species <strong>and</strong><br />
similar systems may exist in less well-studied species, including some of the other great whale<br />
species.