Norwegian researchers at the University of Tromsø have shown that some Arctic animals (ptarmigan, reindeer) show circadian rhythms only in the parts of the year that have daily sunrises and sunsets. In one study of reindeer, animals at 70 degrees North showed circadian rhythms in the autumn, winter and spring, but not in the summer. Reindeer on Svalbard at 78 degrees North showed such rhythms only in autumn and spring. The researchers suspect that other Arctic animals as well may not show circadian rhythms in the constant light of summer and the constant dark of winter. COUNT 5
QSN1 What type of animals have been shown to have circadian rhythms only at certain times? ANS1 Arctic animals QSN2 What daily feature do animals that show limited circadian rhythms need? ANS2 sunrises and sunsets QSN3 In a study, when did reindeer at 70 degrees north only show circadian rhythms? ANS3 autumn, winter and spring QSN4 At what degree north did reindeer show rhythms only in autumn and summer? ANS4 78 degrees QSN5 What aninmals  do researchers think might also show a variance in circadian rhythms in different seasons? ANS5 other Arctic animals