An echidna in Tasmania looks very different from one in Western Australia. But the differences run much deeper than appearance.
A new review by University of Tasmania zoologist Associate Professor Stewart Nicol from the School of Natural Sciences has found echidnas across Australia differ widely in diet, breeding, behaviour and physiology, challenging long-held assumptions that they are the same.
Associate Professor Nicol led a long-term study of Tasmanian echidnas and found they differed far more than expected from the other four recognised regional types, or subspecies.
The differences were so marked that he initially wondered whether there might be several distinct species.
“What’s true for a Tasmanian echidna is not necessarily true for one in the Queensland rainforest or the Western Australian desert,” Associate Professor Nicol said.
In Tasmania, echidnas enter true hibernation in autumn, with body temperatures dropping for months at a time. In desert areas, they experience brief periods of reduced activity.
Breeding varies. Tasmanian mothers wean their young on rich, high-fat milk in as little as 130 days. On Kangaroo Island, the same process can take up to 210 days, with noticeably lower-fat milk.
Even beak shape differs. Desert echidnas tend to have shorter, upward-angled beaks suited to digging for ants and termites. Southern echidnas have longer, flatter beaks for probing deeper into the soil for pasture grubs.
But the genetic evidence tells a more complicated story.
Genetic studies have found little support for the five recognised subspecies, instead splitting echidnas into three groups: New Guinea, eastern Australia and western Australia.
Associate Professor Nicol said the mismatch between biology and genetics could come down to time.
Echidnas are thought to have arrived in Australia from New Guinea during an earlier ice age period, when lower sea levels allowed movement across land.
Fossils suggest they have been in Australia for less than a million years.
Once in Australia, they spread rapidly into very different environments across the continent.
“Echidnas essentially colonised an entire continent and reshaped themselves to suit every corner of it,” Associate Professor Nicol said.
“In geological terms, it happened almost overnight and happened too quickly to be seen in the genetic studies carried out so far.”
Associate Professor Nicol has spent more than 40 years studying echidnas, from early laboratory work to long-term field research.
“The only way to really understand an animal like the echidna is to study it in the field, in its normal habitat,” he said.
The study draws together field observations, genetics and fossil evidence.
One implication is that some classifications may need revision, including Western Australian echidnas that have been grouped with northern Queensland populations but are genetically separate.
“There are big gaps in our knowledge. We now have a lot of information about the most southerly echidnas, but very little has been done with the echidnas in the tropics,” he said.
Associate Professor Nicol is calling for a comprehensive genetic study across Australia and for researchers to clearly identify which populations they are studying.
The findings also have practical implications. Zoos, wildlife carers and conservation managers may rely on general guidelines that only apply to one regional form.
Australia’s echidna is the country’s most widespread native mammal. This research suggests it is also among the most varied.
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