Scientists studying little-known Western Australian north coast dolphins found the populations do not interbreed, meaning their gene pools are small and they could be vulnerable to genetic disease
The Australian snubfin (pictured above) and humpback dolphins occur throughout tropical coastal waters of northern Australia but little is known of their abundance or life history characteristics because much of their range is remote from human centres.
Researchers from Murdoch University’s Cetacean Research Unit have worked with a number of collaborators to produce the first estimates of population genetic structure of two coastal dolphin species of north western Australia.
Both snubfin and humpback dolphins are listed as near threatened but the lack of information about them has prevented a comprehensive assessment of their conservation status.
Large-scale industrial development is occurring across north western Australia, resulting in modification to coastal habitats through dredging, construction and increased shipping.
“With so little data on coastal dolphins in this region, the potential impact of these developments remains unknown,” says Alex Brown.
Using small tissue samples collected with a dart, the researchers compared the genetic characteristics of two populations of each species: snubfin dolphins from Roebuck Bay and Cygnet Bay in the Kimberley region and humpback dolphins from the North West Cape and the Dampier Archipelago in the Pilbara.
“Results showed that there wasn’t much mixing between the populations,” Alex said. “They are fairly isolated, with low levels of gene flow between populations separated by about 300 km of coastline.”
The researchers are urging management agencies to treat the dolphin populations as small, discrete fragments and to preserve corridors for individuals to travel between populations.
In a first, Alex documented the first recorded hybrid between a humpback and snubfin dolphin.
“We were at first puzzled by this unusual looking dolphin,” said Alex.
“At first glance it resembles a humpback dolphin, but a closer look reveals a small beak, shorter than a humpback or bottlenose dolphin, but very different from the rounded, porpoise-like head of a snubfin.”
Genetic analysis revealed it to be the offspring of a snubfin dolphin mother and humpback dolphin father.
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