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Jun. 07, 2007

Land of the Midnight Sun

by Flora Lichtman

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The sun rose at about 3:15 AM today in Fairbanks, AK and will set again at about 12:20 AM. Even after the sun goes down it won’t get dark; twilight remains until the sun rises again. You can see the sun blazing in the picture to the right–it was 9PM when the picture was taken.

I find the constant sunlight a little discombobulating and wondered: does the sun cycle affect the behavior of wildlife in Alaska? A study published in the journal Biological Rhythm Research in 2006, looks at the impacts of continuous sunlight on porcupines and ground squirrels (see picture below) in the Arctic.

G. Edgar Folk, a professor of Physiology and Biophysics at the University of Iowa, and the first author on the paper, and his colleagues explain that animals living in the middle latitudes (with more traditional sun exposure) operate primarily on a 24-hour schedule, called a circadian rhythm.

But, a previous study showed that when lab rats were exposed to continuous light, they developed a 26-hour cycle–the rats’ peak activity came later each day. Folk went into the field to see whether wild animals native to the Arctic developed a longer cycle like the lab rats. But the data showed that the ground squirrel and porcupine maintained a 24-hour-cycle. There are a few possible explanations: although there isn’t complete darkness, the changes in intensity or position of the sun throughout the day may provide environmental cues that could trigger the 24-hour rhythm.

Image (top) credit: Annette Heist

About Flora Lichtman

Flora is the multimedia editor at Science Friday.

The views expressed are those of the author and are not necessarily those of Science Friday.

Science Friday® is produced by the Science Friday Initiative, a 501(c)(3) nonprofit organization.

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