December 2021 – January 2022

The Nation Reviewed

Echidna poo has changed our understanding of human evolution

By Kieran Pender
Illustration by Jeff Fisher
Citizen science is not only helping echidna conservation, but changing how we think about evolution

Every few weeks, unusual packages arrive by post at the University of Adelaide. Sent by dutiful citizen scientists across Australia, they contain biological material that has shed light on the uniqueness of a native Australian icon and inspired new scientific thinking on human evolution: echidna poo.

Since 2017, more than 500 of these deliveries have arrived at the urging of Professor Frank Grützner, Dr Tahlia Perry and their lab team, as part of the Echidna Conservation Science Initiative. Together with an app, on which Australians can upload photos of echidna sightings, the scat samples have helped provide fresh insight into the life of the spiky animal that adorns our five-cent coin.

“One of the really challenging things about working with echidnas is that you never know when you will see them,” explains Grützner. “It can take hundreds of hours to find an echidna, so it is very hard for individual researchers to obtain data. But then you talk to people who say they’ve just seen one in their backyard.”

That frustration was the inspiration for EchidnaCSI, which was recently shortlisted for an Australian Museum Eureka Prize for citizen science. “We’ve just hit now 12,000 echidna sightings,” he says. “There is no way as a researcher you could ever achieve that number – it is the biggest number of echidna sightings of any project.”

It is somewhat surprising that one of the world’s leading experts on such an emblematic Australian animal speaks with a heavy German accent. But ever since Grützner arrived on these shores two decades ago, he has dedicated his career to studying echidnas and their counterpart, platypuses. These are the only living monotremes, distinguished from other mammals by laying eggs rather than giving live birth.

“They have a lot of profile outside Australia,” Grützner says. “There has always been a lot of interest internationally in finding out more about these monotremes because everyone was so intrigued. Whatever biological aspect you look at, they’re just amazing.”

Named after a half-woman, half-snake creature from Greek mythology, the echidna is now found only in Australia and New Guinea. It evolved from a platypus-like aquatic ancestor, adopting a land-based lifestyle perhaps 50 million years ago. Today, echidnas are Australia’s most widespread native mammal, living in habitats that range from deserts to forests, from snow-capped mountains to urban fringes.

Grützner’s research has not just improved our understanding of echidnas. Remarkably, the work of his research team into the echidna sex chromosome has helped reshape scientific knowledge of human evolution. “In understanding their biology, we get amazing insight into the evolution of fundamental aspects of mammals, including humans,” he says.

Traditionally, it was thought that all mammals – humans, whales, bats, dogs, echidnas, the lot – had the same sex chromosomes. In other words, what makes us biologically male or female is the same across mammals, with this sex-causing evolutionary step dating back 300 million years. However, closer scrutiny of monotreme sex chromosomes, first in platypuses and then echidnas, revealed an evolutionary divergence. Humans have one pair – XX in most women, XY in most men. But platypuses have 10 (5X, 5Y) and echidnas nine (5X, 4Y). “When we actually looked at the DNA on these sex chromosomes, it turned out that it was completely different from other mammals,” Grützner says.

This means that the human sex chromosome developed much later than was previously thought, as recently as 180 million years ago, after the monotremes had split off our common evolutionary path. “So instead of having a much earlier evolution of sex chromosomes common to all mammals, we now know that there’s been two sex chromosome origins. It’s completely changed how we are thinking about the sex chromosome evolution in mammals.” All thanks to Australia’s unique monotremes and their poo.

Echidnas are adventurous creatures – they like to roam, can cover up to 2 kilometres per hour with their characteristic waddle and are strong swimmers. “They use their beak as a snorkel,” says Grützner, who often hears from people who have “rescued” a drowning echidna, only for it to head straight back into the water. But with a taste for exploration comes risk, particularly from one of their biggest threats – vehicles.

“Sadly, many echidnas who are hit by cars are not viable – often the injuries are too serious,” says Ellen Kemp, a wildlife-rescue volunteer in the New South Wales Riverina who has been caring for injured echidnas for almost a decade. For the echidnas that survive, Kemp nurses them back to health until they can be returned to the wild. “It’s basically keeping them quiet, keeping them fed and keeping them clean.”

Kemp says caring for baby echidnas – puggles – is particularly special. “They’re like nothing else.” She encourages drivers who hit an echidna to check nearby for babies. “Echidnas don’t have a proper pouch; they just have a muscle that contracts. So, if a mother is hit, that muscle relaxes and the baby rolls away.”

Once an echidna has returned to health, Kemp places it in an escape-proof pen as a halfway house before it is released. “That’s always a really nice stage, making sure they can dig burrows and tear apart logs to find bugs.” Kemp says that, unlike possums or kangaroos, echidnas do not develop any attachment to their carer. “They’re not very emotional,” she says with a laugh, before admitting that’s often not the case for their carers. “It’s the best,” she says of the moment an echidna is released back into the wild. “That’s what it’s all about.”

While Kemp cares for individual echidnas, Grützner hopes that his work will help conservation efforts. Although the echidna is widespread across Australia, little is known about population numbers because of the difficulties tracking them, which EchidnaCSI is hoping to address. The Kangaroo Island short-beaked echidna, a subspecies, has been listed as endangered. The echidna may be hardy and adaptable, but climate change and growing encroachment on their native habitats will increase threats in the years ahead.

“We need to use this research to benefit monotremes,” Grützner says. “We’re the custodians of these fascinating mammals. We have them in our natural environment and we have this responsibility to preserve them into the future. Gaining better knowledge of echidnas is an important step towards better conservation.”

To that end, Grützner and his team recently sequenced the entire echidna genome for the first time, and published it in leading science journal Nature. They hope that sharing the genome with the world will prompt further international research and collaboration. “That’s going to be a really important tool to facilitate research,” Grützner says. Ultimately, advancing our understanding of echidnas will take a lot more hard work. And a bit more poo.

Kieran Pender

Kieran Pender is a writer and lawyer. He is an honorary lecturer at the Australian National University College of Law.

 

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