No jet lag for Arctic reindeer

Research gives insight into circadian rhythm and other adaptations

Photo: Per Harald Olsen / Wikimedia Commons
Can we, like the Svalbard Reindeer, evolve beyond the need for circadian rhythms?

M. Michael Brady
Asker, Norway

In studies of reindeer in the Arctic, scientists at the University of Tromsø found a clue as to why we suffer jet lag, the delayed effect suffered after a long east-west or west-east flight. For instance, a person traveling from Seattle (where this newspaper is published) to Oslo (where this article was written) feels as if the time upon arrival is nine hours earlier than local time. Jet lag arises because like most animals and plants, we have an internal clock, the circadian rhythm, which is on a 24-hour cycle configured by evolution to the Earthbound pattern of daily sunrises and sunsets. That clock cannot be reset as rapidly as imposed by a jet aircraft flight across time zones. Resetting it may take several days—as a rule, one day per time zone crossed. The inconvenience to airline crews as well as passengers is immense.

Today there are an estimated two million reindeer in the high north regions of the Eurasian and North American continents. Of these, some 230,000 are in Norway. They are much studied by researchers at the University of Tromsø, in part because reindeer herding is a prime livelihood in the far north. In recent studies the researchers found that arctic animals, such as ptarmigan and reindeer, showed circadian rhythms only in the parts of the year that have daily sunrises and sunsets. In the Svalbard Reindeer, the sub-species living in the Arctic archipelago at 78°N, they found and in 2005 published the observation that reindeer didn’t show circadian rhythms in the constant light of summer or the constant dark of winter. Ten years later that observation was corroborated in a paper published by the American Physiological Society.

Studies continued on other aspects of the biology of reindeer. In 2011 the University of Tromsø researchers joined with colleagues at the University College London in publishing the finding that Arctic reindeer see light a fifth shorter in wavelength than that seen by humans, as well as most mammals. Reindeer see what we see, as well as a significant part of the ultraviolet light spectrum. That extra ability helps them survive in the Arctic, because lichens, the staple of their winter diet, don’t reflect ultraviolet light. So in foraging, food stands out black in a snowscape.

In 2015 the University of Tromsø researchers joined with colleagues at the Norwegian University of Science and Technology in Trondheim to find scientific explanations for the reindeer’s unique ability to survive in the cold Arctic climate. They found that in addition to their insulating fur, reindeer have a complex nasal system that contributes much to their survival. A reindeer nose acts as a heat exchanger, rapidly warming inhaled air and extracting heat from exhaled air.

Dispensing with the circadian rhythm in constantly light summers and constantly dark winters, perceiving ultraviolet light, and having a heat-exchanger nose are all attributes acquired since reindeer first came to the Arctic 5,000 to 10,000 years ago. The reasons for these differences from similar animals elsewhere on the planet are unknown but suggest that reindeer are a case of evolution in the fast lane.

Further reading: articles in scientific journals accessible via their DOI (Digital Object Identifier) names: Type/paste a DOI name into “Resolve a DOI name” at (be sure to enter all characters before and after the slash) and then click on the SUBMIT button.

• “Circadian organization in reindeer,” by a research group at the University of Tromsø, Nature, Brief Communication, December 21, 2005, link:, DOI 10.1038/4381095a

• “Persistence, Entrainment, and Functions of Circadian Rhythms in Polar Vertebrates,” by C.T. Williams, Physiology (American Physiological Society), Vol 30, No. 2, March 2015, p. 86-96, link:

• “Arctic reindeer extend their visual range into the ultraviolet,” by researchers at the University of Tromsø, the University College London, and the University of Western Australia, Journal of Experimental Biology, issue 214 (June 15, 2011), DOI 10.1242/jeb.053553

• “The Nasal Geometry of the Reindeer Gives Energy-Efficient Respiration,” by Elisa Maganelli and colleagues, Norwegian University of Science and Technology and University of Tromsø, Journal of Non-Eqilibrium Thermodynamics, July 2016, DOI 10.1515/jnet-2016-0038; Popularized version published by Gemini Research News (Norway) December 15, 2016, link:

This article originally appeared in the Jan. 27, 2017, issue of The Norwegian American. To subscribe, visit SUBSCRIBE or call us at (206) 784-4617.

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