This was not the case when the experiment was repeated in the field at the Naval Arctic Research Laboratory - with two species of Arctic rodents exposed to continuous daylight (nocturnal porcupines [Erethizon] N=4, and hibernators, the Arctic ground squirrel [Spermophilis] N=6). Under these circumstances, both species had a specific time of sleep and of wakefulness. In fact, the Arctic rodents, which had undergone 82 days of continuous sun above the horizon, had a crisp, 24-hour day-night rhythm of sleep and wakefulness.

Conclusions

The free-living animals in the Arctic had regular sleep-awake cycles, despite having 82 days of continuous sun. The intriguing question is whether or not these animals have found a clue in the external environment to take the place of the missing sunset. The researchers hypothesize that because the sun during this period is nearer the horizon at one part of the day, this might act as a clue for the biological clocks.

As the American economy requires its work force to abandon traditional work hours of "nine to five," it becomes more important for us to understand how the body's biological clock can respond to unnatural light clues and adapt to a changing environment. This study is another step in the continuing research towards such comprehension.

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Contact: Donna Krupa
djkrupa1@aol.com
703-527-7357
American Physiological Society
19-Apr-2004