This giant marsupial was a seasonal migrant

The largest marsupial to ever walk the Earth is also the only marsupial known to have ever migrated seasonally. Diprotodon optatum was a gigantic wombatlike herbivore that lived in what’s now Australia and New Guinea during the Pleistocene Epoch, until it died out about 40,000 years ago. A new analysis of an ancient tooth suggests that the marsupial went on long, seasonal migrations.

Animals pick up the chemical element strontium through their diet, and it leaves a record in their teeth. The ratio of different strontium isotopes varies from place to place, providing clues to where an animal lived. Strontium isotope ratios in a D. optatum incisor revealed a repeating pattern. The finding suggests the animal, with teeth that wore down and grew throughout its life, migrated seasonally. And the animals generally visited the same rest stops each year, researchers report September 26 in Proceedings of the Royal Society B.

This finding is the first evidence of a marsupial — living or extinct —making round trip migrations, says study coauthor Gilbert Price, a paleoecologist at the University of Queensland in Brisbane, Australia. It’s not clear why this mega-marsupial, which weighed up to 2,800 kilograms, migrated, but an analysis of carbon isotopes in the tooth suggests that D. optatum ate a fairly limited diet. So the creature might have followed food sources that popped up seasonally in different places, the authors propose.