The extinction of the megafauna – giant marsupials that lived in Australia until 60,000 to 45,000 years ago – is a topic of fierce debate. Some researchers have suggested a reliance on certain plants left some species susceptible to changes in climate.

Our research, published today in Science, indicates that for short-faced kangaroos, which comprise the bulk of the extinct megafauna, their diets were broad and comparable to many long-faced kangaroos which survived the extinction event.

Broad diets would have made short-faced kangaroos well adapted to the last ice age in Australia, bringing diet-based extinction scenarios into doubt.

Megafauna is a loose term referring to all the species present in the Pleistocene of Australia (2.6 million to 12,000 years ago) which haven’t survived until today.

Two features unite them: a generally large body size and being extinct. By 40,000 years ago, 90% of large species in Australia had died out.

This included giant flightless birds, the rhino-sized marsupial Diprotodon, marsupial lions and many others.

To investigate this idea, we used a method called dental microwear texture analysis. When an animal chews its food, the food leaves microscopic scratches on its teeth. The shape of these scratches changes based on the physical properties of the food: grasses typically make thin scratches, while leaves create deeper gouges.

By scanning the teeth under a fancy microscope called a confocal profiler, we end up with a 3D-scan of a tiny area of the tooth surface, which can then be analysed using algorithms that quantify its texture.

To see how microwear relates to diet, we compiled a massive baseline of modern macropods whose diets we know really well.

This included 17 species, from browsers (like quokkas, mostly eating the leaves of shrubs), through mixed feeders (like red-necked wallabies, eating large contributions of browse and grass) to grazers (like red kangaroos, who mostly eat grass).

To understand diets in the Pleistocene, we looked at fossils from Victoria Fossil Cave in the Naracoorte Caves World Heritage Area.

We found overall there was a high degree of mixed feeding taking place at Naracoorte in the Pleistocene. Four species of short-faced kangaroos and three species of long-faced kangaroos all had very similar diets – they were mixed feeders.

This alone dispels the notion that all short-faced kangaroos were driven extinct as a direct result of a restricted diet. Mixed feeding is a common strategy among kangaroos today, especially in parts of Australia with more vegetation. It allows species to adapt their diets to changing conditions and mixed environments.To investigate this idea, we used a method called dental microwear texture analysis. When an animal chews its food, the food leaves microscopic scratches on its teeth. The shape of these scratches changes based on the physical properties of the food: grasses typically make thin scratches, while leaves create deeper gouges.

By scanning the teeth under a fancy microscope called a confocal profiler, we end up with a 3D-scan of a tiny area of the tooth surface, which can then be analysed using algorithms that quantify its texture.

To see how microwear relates to diet, we compiled a massive baseline of modern macropods whose diets we know really well.

This included 17 species, from browsers (like quokkas, mostly eating the leaves of shrubs), through mixed feeders (like red-necked wallabies, eating large contributions of browse and grass) to grazers (like red kangaroos, who mostly eat grass).

To understand diets in the Pleistocene, we looked at fossils from Victoria Fossil Cave in the Naracoorte Caves World Heritage Area.

We found overall there was a high degree of mixed feeding taking place at Naracoorte in the Pleistocene. Four species of short-faced kangaroos and three species of long-faced kangaroos all had very similar diets – they were mixed feeders.

This alone dispels the notion that all short-faced kangaroos were driven extinct as a direct result of a restricted diet. Mixed feeding is a common strategy among kangaroos today, especially in parts of Australia with more vegetation. It allows species to adapt their diets to changing conditions and mixed environments.