If you traveled back in time 46,000 years to the Pleistocene epoch in Australia, you would witness a landscape of bizarre creatures. There were giant kangaroos, flightless terror-birds, 23-foot-long lizards, and Tasmanian tigers. Australia, the land of marsupials, was also once home to diprotodon, the biggest marsupial to have ever walked planet Earth.

New research from the Proceedings of the Royal Society B suggests they walked a lot more than any modern marsupial, too. In fact, researchers found that the animal traveled around 120 miles annually—an insight discerned from information locked away for millennia in a single tooth.

Like rats and several other animals, diprotodons had front teeth that would grow continually throughout their lives, being worn down by use. The inside of the long incisors tells a story about what the animal was experiencing as it grew. Specifically, teeth can exhibit chemical signatures from food that the animal ate.

Different places have different soils, and that soil leaves a signature on the plants. By matching the signatures in the tooth to signatures in soil, scientists could tell where the animal had been in its life. Different chemicals found along the length of a diprotodon tooth reveal that it was eating different foods in different places over the course of that tooth’s growth. (Unless the one animal that they studied may have been a rare restless wanderer, but large herbivores usually travel in herds, so it's safe to assume that one tooth represents many.) 

Gilbert Price, a paleontologist at the University of Queensland, led the study. Price and his team drilled samples from the incisor of this monster marsupial. They found that the animal had been traveling to places with different geochemical soil makeups, making its way across the vast expanse of Darling Downs in Queensland, Australia.

Diprotodons looked similar to wombats, with roundish bodies, big noses, and buck teeth. (The word “diprotodon” means “two forward-facing teeth.”) But the prehistoric behemoth dwarfed its modern counterparts. On all fours, it stood six feet tall and could weigh 6,000 pounds.

With this new knowledge of migrating beasts, Price asks the question: what effect did herds of giant, roaming herbivores have on the landscape? We know that migrating herbivores like zebra and wildebeests are critically important keystone species for the African serengeti. Whether these beasts were, too, is a matter for further research.

There are still more unanswered questions about the Australian Pleistocene. What other marsupials migrated? What factors drove so many of them to extinction? What did those extinctions do to their ecosystem—and what will be the effect of current extinctions on ours?