Prehistoric Kangaroos Died Out After Their Rainforest Habitat Disappeared
Today, kangaroos hop across the outback and survive droughts by traveling in groups. But in the past, kangaroos were much bigger, living alongside monstrous reptiles and enormous birds.
A new study has found that giant kangaroos once lived in eastern Australia, and they were much less adaptable, which made them vulnerable to changes in the local environment. They died out after their rainforest habitat disappeared.
Researchers discovered fossilized teeth of the now-extinct genus of giant kangaroo called Protemnodon at Mount Etna Caves in central-eastern Queensland.
Some individuals were as heavy as 375 pounds. Despite its large size, Protemnodon did not travel across great distances.
Instead, it lived in a small stretch of lush rainforest that was like their own utopia. But as the climate became drier with more pronounced seasons, their rainforest habitat began to decline, spelling trouble for the species’ survival. Eventually, they were replaced by those adapted to a dry, arid climate.
The Mount Etna Caves National Park and nearby Capricorn Caves are like a historical record, keeping track of life over hundreds of thousands of years. The caves contain many fossils because they acted like large pits that trapped animals.
In addition, they served as the lairs of predators like thylacines, Tasmanian devils, raptors, owls, marsupial lions, and the now-endangered ghost bats.
Parts of the region used to be mined for limestone and cement. The researchers worked with mine managers to make sure that fossils were safely removed from rundown caves.
They used methods called uranium-series dating and luminescence dating to study the fossils and the surrounding sediment.
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The findings suggest that the kangaroos lived near the caves from at least 500,000 years ago to about 280,000 years ago. They disappeared from the fossil record after this period.
Between 280,000 and 205,000 years ago, the climate became drier, and Protemnodon vanished from the region.
The research team examined the tooth enamel of Protemnodon to determine their foraging ranges and found that the species did not travel very far.
They likely did not need to travel to find food because the rainforest had evolved over millions of years to have a stable food supply.
Fossil evidence also suggests that Protemnodon walked on all fours rather than hopped, which would have limited their ability to cross long distances, but was great for living in a rainforest.
“Using data from modern kangaroos, we predicted these giant extinct kangaroos would have much larger home ranges. We were astounded to find that they didn’t move far at all, with ranges mirroring smaller modern kangaroo species,” said Christopher Laurikainen Gaete, the lead author of the study at the University of Wollongong.
Creatures with a small home range are basically doomed if something happens to their local habitat. The kangaroos’ biology, which made them perfectly suited to rainforest life, ended up becoming their downfall as they were unable to travel elsewhere.
The study was published in PLOS One.
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