Time capsules from the Ice Age

It is late August, and the weather is turning cold. Very cold. A little chubby arctic ground squirrel bounds at surprising speed across the prairie. It pauses briefly, standing on those two short little back legs. Ears twitching, listening. There are other things out on the prairie; bigger things. Swift foxes, silent eagles, ferocious wolverines, and even grizzly bears all of which will happily guzzle one of these fuzzy critters down for a snack. Not a peep. She moves on swiftly to luscious vegetation, the patches of her silvery fur shimmering in the mid-day sun. She stuffs seeds and flowers in her mouth and grabs some grass before bouncing back to her underground home. Here, her home is at the end of a small tunnel she has dug out of the soft earth herself. It is welcoming: packed full of comfy moss and grass to sleep on, and plenty of seeds to feed on. What she has brought back isn’t enough. She needs more, so scurries out to collect more, and more and more until the winter begins. The cold winds and icy rain tell the little creature that winter is coming. Quickly she darts inside the safety of her burrow. She snuggles up in her nest of the softest lichen, moss and grass, and drifts to sleep.

20,000 years later, she is found. Mummified in her nest, still curled up, eternally asleep. This arctic ground squirrel never woke up from her hibernation.

"Squirrel Mummy" by Ryan Somma - Squirrel MummyUploaded by FunkMonk. Licensed under CC BY-SA 2.0 via Commons - https://commons.wikimedia.org/wiki/File:Squirrel_Mummy.jpg#/media/File:Squirrel_Mummy.jpg

A mummified Arctic Ground Squirrel from Alaska. 20,000 years ago this squirrel curled up and went to sleep. But never woke up. (Image by Ryan Somma, Public Domain)

Arctic ground squirrels (Spermophilus parryii) are still around today, and it is more than likely you have seen them on a nature documentary. They are gorgeous little creatures, always busy, constantly gathering bits of the landscape to make their nests or to store in their larder for when they wake from their hibernation. They look out for each other on the open prairie, and give little growls or high pitch squeaks to warn others of approaching predators. Their soft, fluffy fur is light brown with soft red spots on in the summer, which changes to silver spots in the winter.

These are really cool little things. As their name suggests, these gopher-like animals that live in the cold northern environments (Siberia, North Canada, Alaska, and the Arctic Circle). Because they live in places where it is so far north that the sun never sets in the summer, their brains don’t have a body clock. Waking late in the morning and sleeping early in the afternoon means that they are more energy efficient when it is ‘warmest’ during the middle of the day (looking for a mate, or gathering food early or later in the day uses up more energy to stay warm because it is colder). Inside their small self-made nests, not very deep underground, they spend the freezing Alaskan winters hibernating. Here temperatures can fall to well below freezing. What is incredible is that they can lower their body temperatures from around 37oC to around -2oC while they hibernate.

"Spermophilus parryii (eating mushroom)" by Ianaré Sévi - Own work. Licensed under CC BY-SA 3.0 via Commons - https://commons.wikimedia.org/wiki/File:Spermophilus_parryii_(eating_mushroom).jpg#/media/File:Spermophilus_parryii_(eating_mushroom).jpg

The adorable Arctic Ground Squirrel (Spermophilus parryii), here nibbling on a mushroom. (Image by Ianaré Sévi, Public Domain)

These guys are nature’s true collectors. Their nests are full of twigs, grasses, seeds, and flowers of their immediate environment. And this is very exciting because they have been doing this for tens of thousands of years. Their great-great-great (x 20) grandparents were scooting beneath the feet of Woolly Mammoths, Bison and other Ice Age beasts. An added bonus (for palaeontologists) of building homes underground is that these extremely fragile nests are preserved.  These are true time capsules from the Ice age. Canada’s northern territory, the Yukon, along with central Alaska, has been a hot spot for arctic ground squirrel research. Not only have fossils dating back around 47,000 years been found, but huge numbers of their nests have been recovered.

Some sites have dozens of nests exposed at certain layers; all that’s left of an ancient colony. And nests can be found in different layers too; giving a nice glimpse into different periods of the past. What gets me so excited about arctic ground squirrel nests is what we can find inside them.

Images of ground squirrel bones found in tunnel near Dawson City, 2003. (Image ©Grant Zazula/Duane Froese)

This may look like at picture of mud, but it is actually super sexy. Look in the middle of the picture, just to the left of the zip-lock back, and you can spy a twig poking out of the soft mud: this is the nest of an arctic ground squirrel! And the nest contained bones!! (Image ©Grant Zazula/Duane Froese 2003)

In the Yukon and central Alaska, between 47,000 and 11,000 years ago nests are full of buttercups, poppy seeds, wild rye grasses, dwarf shrubs, and very few trees. Wonderful you may think. It really is, when you throw in that Mammoths were lolloping in the Yukon at the same time! So from these time capsules we know what the environment was like. It was cold, but dry. There were few trees around, and this formed part of the Mammoth Steppe which stretched all across the northern hemisphere. And what we can see from the nests is that there was plenty of food for the Mammoths to feast on.

As well as being a vital part to today’s ecosystem, arctic ground squirrels are key to understanding prehistoric ecosystems. Being such obsessive collectors, they create natural time capsules when provide details about time long gone.

Written by Jan Freedman(@JanFreedman)

Further Reading:

Barnes, B. M. (1989). ‘Freeze avoidance in a mammal: body temperatures below 0oC in an arctic hibernator.’ Science (American Association for the Advancement of Science). 244. pp.1593-1595. [Full article]

Batzli, G. O. & Sobaski, S. T. (1980). ‘Distribution, abundance and foraging patterns of ground squirrels near Atkasook, Alaska.’ Arctic and Alpine Research. 12. pp.501–510. [Abstract only]

Betancourt, J. L., Van Devender, T. R., & Martin, P. S. (1990). ‘Packrat Middens: The last 40,000 years of biotic change.’ University of Arizona Press, Tuscon, AZ. [Book]

Buck, C. L. et al. (2008). ‘Overwinter body temperature patterns in free-living Arctic Ground Squirrels (Spermophilus parryii).’ Hypometabolism in Animals: Hibernation, Torpor and Cryobiology: pp.317–326. [Full article]

Buck, C. L. & Barnes, B. M. (1999). ‘Annual cycle of body composition and hibernation in free-living arctic ground squirrels.’ Journal of Mammology 80 (2): pp.430–442. [Full article]

Elias, S.A. (2000). ‘Late Pleistocene climates of Beringia, based on fossil beetle analysis.’ Quaternary Research. 53. pp.229–235. [Abstract only]

Guthrie, R.D. (1990). ‘Frozen Fauna of the Mammoth Steppe: The Story of Blue Babe.’ University of Chicago Press, Chicago. [Book]

Guthrie, R. D. (2001). ‘Origin and causes of the mammoth steppe: a story of cloud cover, woolly mammal tooth pits, buckles, and inside-out Beringia.’ Quaternary Science Reviews. 20. pp.549–574. [Abstract only]

Liu Y, et al. (2010). ‘Genomic analysis of miRNAs in an extreme mammalian hibernator, the Arctic Ground Squirrel.’ Physiological Genomics. 42A. pp.39-51. [Full article]

Nadler, C. F. & Hoffmann, R. S. (1977). ‘Patterns of evolution and migration in the Arctic ground squirrel Spermophilus parryii (Richardson).’ Canadian Journal of Zoology. 55. pp.748–758. [Abstract only]

Zazula, G. D., et al. (2007). ‘Arctic ground squirrels of the mammoth-steppe: paleoecolgy of Late Pleistocene middens (24,000-29,450 14C yr BP), Yukon Territory, Canada.’ Quaternary Science Reviews. 26. pp.979-1003. [Full article]



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6 Responses to Time capsules from the Ice Age

  1. kerberos616 says:

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