LIFE AT A PLIOCENE BEAVER POND IN THE CANADIAN ARCTIC

About 4 million years ago a beaver pond existed on what is now Canada's northernmost island, Ellesmere Island. The site (78°33'N) was discovered by Geological Survey of Canada geologist John Fyles in 1961. This small exposure of peaty, fossil-bearing beds has produced tree trunks up to 3 m-long, many beaver-cut sticks (some burned by forest fires), remains of freshwater mollusks, insects, pollen, plant macrofossils and vertebrates.

These fossils give the first insight into what terrestrial life was like in the High Arctic during the Early Pliocene about 4 million years ago. The vertebrate remains are particularly interesting, consisting of fishes, frogs, birds and mammals, including new taxa of shrew, mouse, badger and “deerlet”. Bones most commonly found represent a small extinct beaver (Dipoides), rabbit (Hypolagus), and primitive black bear (Ursus abstrusus), as well as several members of the weasel family. Another remarkable find was of a three-toed horse, like Plesiohipparion. Many of these species are related to Early Pliocene (about 6 to 4 million years ago) mammals from the Yushe Basin in northern China.

Studies of pollen and plant macrofossils indicate a larch-dominated boreal forest margin habitat with grassy patches surrounding the beaver pond. Moss and vascular plant fossils mainly represent wetland species. Analysis of the beetle fauna from the peaty matrix indicates that the site was 10°C warmer than present in summer and 15°C warmer in winter. Isotopic studies of fossil larch support this view. The boreal-forest margin environment of the site is similar to that of the Yukon today.