Large-bodied extinct kangaroos of the genus Protemnodon were not intrepid travelers who bounded across the plains, but rather homebodies, who did not journey far throughout the course of their lives, according to new research by paleontologists from the University of Wollongong, the University of Adelaide, Queensland Museum and Monash University. The discovery mirrors the behavior of modern species of kangaroos but was surprising to the authors.

In large mammalian herbivores, bigger body size is often correlated with a wider home range, but whether this is true for extinct Australian megaherbivores is unclear.

In a new study, University of Wollongong paleontologist Christopher Laurikainen Gaete and his colleagues focused on Protemnodon fossils discovered in Mt Etna Caves, north of Rockhampton in central Queensland, Australia.

They analyzed strontium isotopes from kangaroo teeth and found a match only to local limestones, rather than distant rock formations.

“Strontium isotopes in animals’ fossilized teeth reflect the geology of the region where it found its food,” they explained.

The results imply that Protemnodon had a much smaller foraging range than might be expected based on body size, estimated at up to 170 kilograms.

Previous research suggests that Protemnodon were not capable of long-distance bipedal hopping due to their large size, and body shape, which in turn may have limited their capacity to roam.

The new study proposes that a stable and lush rainforest habitat would have provided enough food that Protemnodon had no need to range farther.

When changing climate and increasing aridity disrupted this rainforest environment around 280,000 years ago, small foraging ranges may have left Protemnodon unable to find greener pastures, leading to the local extinction of these giant kangaroos

Further research will be needed to determine if it was a common pattern for Australian giant marsupial home ranges to be correlated more with their habitat than their body size.

“Using data from modern kangaroos, we predicted these giant extinct kangaroos would have much larger home ranges,” Laurikainen Gaete said.

“We were astounded to find that they didn’t move far at all, with ranges mirroring smaller modern kangaroo species.”

“These new isotopic techniques have blown our field wide open,” said Dr. Scott Hocknull, senior scientist and curator at Queensland Museum and a paleontologist at Monash University.

“Imagine ancient GPS trackers — we can use the fossils to track individuals and know where they moved, what they ate, who they lived with and how they died. It’s Paleo Big Brother.”

“The debate about the extinction of the Australian megafauna has been going on for decades, but now we can take it to an individual and species-by-species perspective,” said Professor Anthony Dosseto, a paleontologist at the University of Wollongong.

“With these precise techniques, each site and each individual, can now be used to test and build more accurate extinction scenarios.”

The scientists now plan to use these same techniques to reconstruct the past behaviors and diets of other extinct kangaroo species from the Mt Etna and Capricorn Caves region.

“Many of the kangaroos found as fossils at Mt Etna and Capricorn Caves, including tree kangaroos, pademelons, and rock wallabies, have living descendants in the Wet Tropics and Papua New Guinea,” Professor Dosseto said.

“We will now apply these same techniques to understand how these surviving kangaroo species responded to the same environmental changes that drove the megafauna extinct.”

The study will be published in the journal PLoS ONE.

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C. Laurikainen Gaete et al. 2025. Megafauna mobility: Assessing the foraging range of an extinct macropodid from central eastern Queensland, Australia. PLoS ONE 20 (4): e0319712; doi: 10.1371/journal.pone.0319712