Research Indicates That the Size of Small Houses Made Ancient Giant Kangaroos Susceptible to Local Extinction

Extinct Kangaroos from the genus Protemnodon A recent study by paleontologists from the University of Adelaide, Queensland Museum, and Monash University discovered that these creatures were not adventurous wanderers traversing the plains, but rather homebodies that remained close to their habitats throughout their lives. This finding aligns with behaviors observed in modern kangaroo species, yet it was surprising to the researchers.

Among large herbivorous mammals, greater body sizes are often associated with broader foraging ranges; however, it remains uncertain if this trend applies to extinct Australian megafauna.

In this study, paleontologist Christopher Laurikainen Gaete and colleagues investigated protemnodon fossils found in the Etna Cave, located north of Rockhampton in Central Queensland, Australia.

They examined strontium isotopes from kangaroo teeth, revealing matches only with local limestone rather than distant rock formations.

“The strontium isotopes in the fossilized teeth indicate the geology of the region where food was sourced,” they noted.

The findings suggest that Protemnodon had a significantly smaller foraging range than anticipated for its size, which is estimated at up to 170 kilograms.

Prior research indicates that Protemnodon likely lacked the capacity for long-distance travel due to its large size, thereby restricting its movement.

Additionally, this new study suggests that the stable, lush rainforest habitat provided sufficient food sources, negating the need for Protemnodon to wander far.

When climate change and increasing aridity disrupted this rainforest ecosystem about 280,000 years ago, the reduced foraging area may have left Protemnodon unable to find sufficient food, ultimately leading to the local extinction of these giant kangaroos.

Further investigations are needed to ascertain whether the limited range of Australia’s gigantic marsupials is a widespread pattern attributable to habitat rather than body size.

“We utilized data from contemporary kangaroos to predict a much broader foraging range for these giant extinct kangaroos,” explained Laurikainen Gaete.

“We were astonished to find they didn’t roam at all.”

“These innovative isotopic techniques have significantly advanced our field,” remarked Dr. Scott Hocknall, a senior scientist and curator at the Queensland Museum and paleontologist at Monash University.

“Think of it as an ancient GPS tracker. Fossils allow us to monitor individual movement, dietary habits, social interactions, and causes of death.”

“The ongoing debate regarding the extinction of Australia’s megafauna has persisted for decades, and now we can analyze it from an individual and species-specific standpoint,” stated Professor Anthony Doset, a paleontologist at the University of Wollongong.

“These precise methodologies enable us to examine each site and individual, facilitating more accurate extinction models.”

Researchers are currently planning to apply these methods to reconstruct the past behaviors and diets of MT ETNA and other extinct kangaroo species in the Capricorn Cave region.

“Many of the kangaroo species on Kangaroo Island, such as those found in Capricorn Caves, include tree kangaroos, pademelons, and rock wallabies, with descendants inhabiting the wet tropics and Papua New Guinea,” noted Professor Doset.

“We will employ these same techniques to explore how these surviving kangaroo species adapted to the environmental changes that contributed to the massive extinctions.”

The study will be published in the journal PLOS 1.

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C. Laurikainen Gaete et al. 2025. Megafauna Mobility: An assessment of the foraging range of extinct macropodids from central Queensland, Australia. PLOS 1 20(4): E0319712; doi: 10.1371/journal.pone.0319712