The Tasmanian emu might not be as famous as other extinct species, but new research is shedding light on the sizable bird.
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An analysis of emu fossils by researchers at the University of Adelaide has revealed that living on smaller islands with limited resources may have driven the birds to become smaller over time.
The findings published in the Biology Letters journal, showed emus that lived isolated on Australia’s offshore islands until the 19th century, including Kangaroo Island, King Island and Tasmania, were smaller versions of their mainland relatives.
The study’s lead author, Australian Research Council Discovery Early Career Research award fellow Dr Vicki Thomson, said the research had revealed new information about the evolutionary relationships between the species.
“Our results have shown that all the island emus are genetically closely related to the much larger mainland emu,” Dr Thomson said.
“The leg bones, a measure of overall body size, show size differences from the smallest, found on King Island, to the largest, on the mainland, with Kangaroo Island and Tasmanian emus in between.
“The smallest, the King Island emus, are typically two-thirds of the size of our mainland emus, with others ranging upwards according to the size of their island.”
The study’s co-author, post-doctoral research associate Dr Kieren Mitchell, said the island’s size and food sources were contributing factors to consider.
“This [study] suggests that island size, and presumably the associated reduced food resources available, may have been important in causing smaller body size in island emus,” he said.
Dr Thomson said further research was needed to confirm more about how island size contributed to the smaller stature of the extinct island emus.
“We do know that prior to European arrival, Kangaroo Island, King Island and Tasmania had these smaller bodied emus and they would have been isolated from the mainland after sea-levels rose around 10,000 to 15,000 years ago,” he said.
“The change in body size thus appears to have happened quite quickly, and independently on each island.”
The Tasmanian emu subspecies is believed to have become extinct in the mid 19th century and were previously hunted as pests.
Jessica Willard
Being a health reporter to me is about more than just reporting the problems. It's about asking why they are happening in the first place and what needs to change to fix it.
Being a health reporter to me is about more than just reporting the problems. It's about asking why they are happening in the first place and what needs to change to fix it.
