Rock wallaby fossils show they weren’t all homebodies
Rock wallabies may not all be shy, cliff-dwelling housebodies as thought.
Fossil evidence suggests that a few ancient individuals traveled far afield to find others of their kind, improving genetic diversity and long-term population resilience in the process.
The findings of a team of Australian scientists have implications for contemporary conservation efforts to protect rock kangaroo species.
They say that as major roads and industrial and residential developments now carve up the land, people are unintentionally creating barriers to these rare but important dispersal events.
“Future management should not view rock wallabies as isolated colonies,” said lead researcher Chris Laurikainen Gaete from the University of Wollongong.
“Long-distance dispersal has always been part of their natural history, and by preserving landscape connectivity we ensure that this deep-time behavior remains part of their survival in the future.”
Evidence of such distributions in fossil wallabies was made possible by examining their teeth, which contain unique chemicals from the food they ate and are therefore linked to the underlying geology.
“So any plant growing on limestone will have a unique signature. A plant growing on basalt rock will have a different signature,” Mr Laurikainen Gaete told AAP.
“We know the caves are in the limestone block, so if they are local they would actually have a limestone signature.
“But if they were feeding elsewhere in the landscape, we’d see a different signature, so that’s how we know where they are.”
Mr Laurikainen Gaete said the next step would be to apply the same technique to live wallaby colonies, as part of which road kills and genetic testing would also be carried out.
This could determine where the animals started and how far they moved through the landscape before dying, he said.
The study, published in Quaternary Science Reviews, found that most rock wallabies living in central Queensland about 280,000 years ago occupied small home ranges, but a few individuals were unexpectedly mobile.
He traveled more than 60km, including at least one crossing the crocodile-infested Fitzroy River.
Some studies of modern rock wallabies have suggested gene flow between colonies.
But the fossil study is the first direct evidence that long-distance dispersal occurred in individual rock wallabies, preserving connections between isolated populations and supporting genetic diversity.
Researchers analyzed fossil remains from the Mount Etna Caves near Rockhampton.
“We used chemical signatures preserved in fossil teeth to reconstruct how individual kangaroos moved across the landscape,” said Professor Anthony Dosseto from the Wollongong Isotope Geochronology Laboratory.
“With a few notable and important exceptions, most were homesteaders relying on local resources.”
Palaeontologist Dr Scott Hocknull, from CQ University, said the study demonstrated the power of new isotopic techniques to reconstruct ancient animal behavior at the individual level.
“The long-term survival of species depends on the ability of individuals to move between habitats,” he said.
