BOBO ИЌ d 9 9 9 9 9 9п+ Йќ џџ XБ Й , џџ И№џџ џ - Z џџџ Richard Northover f џџ B LOM! ` 9y џџ џ x H H џ§aѕ(ќ § Ф Ы lР Д - ^ь & ' џџ Й P l / Рc х е Й8 Иф Й хc Иѓ0 ЗЌd Й [ф џџџџџџџџ ] Qy DSET T ј љ - И ЙЈЖВ Иѕ8 ђІИа #0 h М Н љ , - Йl _ШИѕЌ 'Иѕ _Dolphins
Dolphins are great communicators - they keep track of each other in constantly changing social groups by using a range of vocalisations, or 'whistles', which they learn from those around them. For some time, scientists have been interested in the fact that individuals seem to develop their own 'signature whistles', which they use to identi Шfy themselves. But the behaviour of male dolphins in Western Australia has suggested that individual identity may sometimes be relinquished in favour of group identity.
Male dolphins often group together and co-operate closely when courting females or competing with other males for mates. These groups work because each member of a team gets a better chance of mating than if he was on his own - teams can herd females more successfully, for example, and males who can perform difficult synchronised swimming routines can demonstrate how strong and healthy they are.
Rachel Smolker of the University of Michigan and John Pepper of the University of Vermont studied bottlenose dolphins in Shark Bay at Australia's westernmost point. They followed three males that had formed an alliance, and over several years, recorded the dolphins' whistles. Using computers to analyse these sounds, the researchers found that, as the alliance grew stronger and the three males co -operated more and more, their individual whistle repertoires began to narrow. Eventually, their signature whistles converged to form one team call.
Smolker and Pepper suggest that having a group signature may strengthen the message given out to other dolphins, acting as a badge for gang members and calling attention to the alliance as a force to be reckoned with. The males' ability to co-ordinate their behaviour in this way may also be attractive to females. (Ethology, vol. 105, pp595-617). Richard Northover
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