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Hidden cameras reveal Rottnest Island bobtails under attack by ravens

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Ravens on Western Australia’s popular tourism destination Rottnest Island have been caught preying on the island’s bobtails by hidden cameras as part of new Curtin University research.

The research, published in Wildlife Research, used clay model bobtails and hidden cameras to examine the attacks on bobtails based on their distance from the Thomson Bay settlement on Rottnest Island, a small island located about 18km west of Fremantle.

Research author Dr Bill Bateman, from Curtin University’s School of Molecular and Life Sciences, said 96 clay model bobtails recorded 1450 indentations over a 28-day period with the majority, almost 80 per cent, caused by ravens and the remainder by curious quokkas and house mice.

“This study indicates that ravens may be actively attacking Rottnest Island bobtails and also suggests those attacks are not affected by the distance from the main settlement at Thomson Bay, even though ravens are in greater numbers near the settlement,” Dr Bateman said.

“Despite more cover being available for bobtails in areas with denser vegetation, we found raven attacks were more frequent in those areas than other sites with more open vegetation. This finding suggests that, even where this is cover for the bobtails, ravens perched nearby can still find them.”

Dr Bateman said ravens had previously been noted to follow researchers between study sites and cameras recorded them visiting the site within five minutes of the researchers’ departure, indicating ravens linked human presence with feeding opportunities.

He said Rottnest Island’s proximity to the Western Australian mainland and its attraction as a tourism destination meant a complete eradication of ravens was unlikely.

“Ravens and bobtails have doubtless always coexisted on the island but the raven population is known to have increased over time,” Dr Bateman said.

“In order to control the population of ravens and to help the bobtails on Rottnest Island, this research suggests authorities should continue their good work in increasing public awareness of reducing food waste that helps support the ravens on the island, before considering culling.”

The research, which was supported by Curtin University and the Rottnest Island Authority, also involved researchers from Edith Cowan University.

The full paper, ‘Bad news for bobtails: understanding predatory behaviour of a resource-subsidised corvid towards an island endemic reptile’, can be viewed online here.

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