New NSF-Funded, University of Colorado Research shows 53-million-year-old Arctic Mammals Wintered in Darkness

Professor Jaelyn Eberle

University of Colorado
Jaelyn Eberle, of the University of Colorado at Boulder, left,
searches for early mammal fossils in the high Arctic


Ancestors of tapirs and ancient cousins of rhinos living above the Arctic Circle 53 million years ago endured six months of darkness each year in a far milder climate than today that featured lush, swampy forests, according to a new NSF-supported study led by the University of Colorado at Boulder.

Jaelyn Eberle, an assistant professor at the university,  said the study shows several varieties of prehistoric mammals as heavy as 1,000 pounds each lived on what is today Ellesmere Island near Greenland on a summer diet of flowering plants, deciduous leaves and aquatic vegetation.

But in winter’s twilight they apparently switched over to foods like twigs, leaf litter, evergreen needles and fungi, said Eberle, curator of fossil vertebrates at the University of Colorado Museum of Natural History and chief study author.

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.

A paper on the subject co-authored by Henry Fricke of Colorado College in Colorado Springs and John Humphrey of the Colorado School of Mines in Golden appears in the June issue of Geology.

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