Ancient squirrel nest found in Yukon

Nov 03, 2005, vol. 34, no. 6
By Diane Luckow

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The fossilized remains of 25,000-year-old ground squirrel nests are shedding new light on the flora and fauna of the Yukon during the last ice age.

The fossils, discovered in the Dawson city area by SFU doctoral student Grant Zazula, his supervisor, SFU professor of biology Rolf Mathewes and their team of colleagues from the universities of Toronto, Alberta and London, England, reveal information about the botanical and ecological significance of the area.

Frozen in permafrost for tens of thousands of years, the nests contain fossilized caches of food, seeds, bones and fecal pellets. These remains detail an unprecedented picture of a rich landscape characterized by tundra and arctic grassland plants during harsh ice-age climates.

“Almost all of the plant species found in the nests aren't found in the area today,” says Zazula.

Most of them are presently restricted to high alpine tundra or in rare habitats such as dry prairies or salt flats. In fact, ground squirrels are no longer found at the fossil sites because they can't tunnel through the permafrost.

But during the last ice age, says Zazula, the area was a cold, dry grassland tundra with soils perfect for burrowing. The ground squirrels' fecal pellets likely fertilized the soil, creating nutritious vegetation for the woolly mammoths and bison also known to have inhabited the area.

Yet most paleontology in the arctic is focused on large animals like bison, says Zazula. Comparing the fossil plant remains with what is known about the ground squirrel's diet in present day tundra indicates their diet hasn't changed much over several thousand years, demonstrating their ability to adapt to pronounced ecological change.

“Looking at some of these little creatures might tell us more about environmental change, evolution and adaptations,” says Zazula, “since it seems that they were a really important part of the Arctic ecosystem.”

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