A newly published study by Canadian and American researchers has revealed a better understanding of the migration and evolution of the large mammals that once inhabited a warmer, ancient Arctic. 

Headed by curator of fossil vertebrates at the University of Colorado’s Museum of Natural History, paleontologist Jaelyn Eberle, the study “may provide the behavioral smoking gun for how modern groups of mammals like ungulates — ancestors of today’s horses and cattle — and true primates arrived in North America.”

The research team analyzed isotopes that were discovered in the 53 million year old teeth of large animals resembling hippos.  The fossilized teeth were discovered on Ellesmere Island.  The isotopes contained information about the timing of the animals’ migration and reproduction, along with what plants they ate, and where these plants were located.

Besides the teeth from the hippo-like animal (the Coryphodon), teeth from one of the ancestors of the tapir and an animal resembling a rhinoceros (the brontothere) were also studied.

In a summary of the study that was released yesterday, Eberle said, “We were able to use carbon signatures preserved in the tooth enamel to show that these mammals did not migrate or hibernate. Instead, they lived in the high Arctic all year long, munching on some unusual things during the dark winter months.”

It is believed that the animals ate mostly leaves and flowering plants during the summer months, switching to twigs, fungi and pine needles for nourishment in the winter.

 “In order for mammals to have covered the great distances across land bridges that once connected the continents,” Eberle said, “they would have required the ability to inhabit the High Arctic year-round in proximity to these land bridges. The study has implications for the dispersal of early mammals across polar land bridges into North America and for modern mammals that likely will begin moving north if Earth’s climate continues to warm.”