Scientists stalking a small marsupial through a remote Australian rainforest say they may have found a clue to the mystery of why its bigger kangaroo cousins hop instead of walk.
Kangaroos and closely related wallabies are the only large animals to hop upright on two legs, researchers from Australia’s Flinders University said Thursday, but why remains a mystery.
They believe the answer may lie with the small musky rat-kangaroo, a bush-dwelling marsupial weighing about the same as a loaf of bread.
Musky rat-kangaroos are a distant ancestor of the larger kangaroo species that roam the outback.
Researcher Amy Tschirn said musky rat-kangaroos – named for their pungent scent – were the only members of the “macropodoid” family that did not hop.
“The musky rat-kangaroo provides a crucial insight into how and when the iconic hopping form of locomotion evolved in Australia,” she said.
Scientists tracked the creatures, also known as “muskies”, through far-north Queensland’s tropical rainforests.
They observed the creatures moving in a “bounding” motion – hopping with their back legs while their front paws remained on the ground.
It suggested a kind of mid-point in the evolutionary journey from walking on all fours to hopping on two, the researchers said.
“These results signal a potential pathway to how bipedal hopping evolved in kangaroos,” said Harvard University biologist Peter Bishop, who was involved in the work.
“Perhaps it started with an ancestor that moved about on all fours like other marsupials, then an animal that bounded like the muskies, and finally evolved into the iconic hopping kangaroos we see in Australia today.,” he said.
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Kangaroos and wallabies are the only hopping species heavier than 5kg, the researchers said.
Some smaller rodent species also hop.
The researchers said they hoped to find fossils of ancient marsupials to better understand the evolution of modern-day kangaroos.
Their findings were published Thursday in peer-reviewed journal Australian Mammalogy.
