Context: 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.

Question: What type of animals have been shown to have circadian rhythms only at certain times?
Answer: Arctic animals

Question: What daily feature do animals that show limited circadian rhythms need?
Answer: sunrises and sunsets

Question: In a study, when did reindeer at 70 degrees north only show circadian rhythms?
Answer: autumn, winter and spring

Question: At what degree north did reindeer show rhythms only in autumn and summer?
Answer: 78 degrees

Question: What aninmals  do researchers think might also show a variance in circadian rhythms in different seasons?
Answer: other Arctic animals

Question: When do subarctic animals have circadian rythms?
Answer: Unanswerable

Question: When do reindeer below 70 degrees show circadian rythems?
Answer: Unanswerable

Question: What reinder at 78 degrees do not show circadian rythems?
Answer: Unanswerable

Question: What animals show circadian rythems during the costant light of summer?
Answer: Unanswerable