An analysis of dolphin genes has revealed information about their past migrations, showing just how crucial migrants might be for other populations.
A new study by an international team of researchers found that one Western Australian dolphin population was once an important source of migrants – that is, dolphins that support nearby populations.
The researchers analysed the genetic variants in bottlenose dolphins (Tursiops aduncus) to find out about past dolphin migration.
Lead author Dr Oliver Manlik, Conjoint Associate Lecturer at University of New South Wales, who is also an assistant professor at the United Arab Emirates University, said: “These dolphin migrants from Bunbury were likely important in supporting the stability of nearby populations.”
“Dolphins have no borders, and persistence of animal populations often depends on a ‘rescue effect’, a scenario in which a declining population is ‘rescued’ from extinction by immigrants from other populations.
“These coastal dolphins do not go on any migration ‘journeys’, like some whales and offshore dolphins do.
“Rather, they disperse, which means that some dolphins move from one population to another and reproduce with individuals of the other population, and leave their offspring and genes behind – that’s how we detected this pattern.”
A previous study had shown that the Bunbury dolphin population may decline because they were not producing enough offspring.
“If that is now true, then the Bunbury dolphins may no longer be able to continue supplying emigrants to support other populations, putting these other dolphin populations at risk as well,” Dr Manlik said.
The previous study also showed that reproduction is key to the persistence of the Bunbury population, and, if undisturbed, it is possible that the Bunbury dolphins would produce more offspring again.
“In that case, the Bunbury population might be ok, and will be able to support its neighbouring populations again,” Dr Manlik said.
Co-author Dr Delphine Chabanne, of Murdoch University, has been studying these dolphins in Australia for more than a decade.
“For the conservation of these dolphin populations, it is important to monitor them closely, and, in particular, to keep a close eye on the reproduction of the Bunbury dolphins,” she said.
Co-author Professor Bill Sherwin said Bunbury’s dolphin populations were key to the species’ conservation.
“Genes are information. They can tell us whether populations are isolated or connected, and shed light on migration patterns of the past – important information for wildlife conservation,” he said.
“We now know that we need to focus on the Bunbury dolphins, and especially on their reproductive rates, to protect several dolphin populations.”
The new study, published in the journal Marine Mammal Science, provides an illustration of how modern genetics can use information from genes to gain a glimpse into the past, unravelling past migration patterns of animals, and therefore helping to inform the future.
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