Arc­tic rein­deer threw the clock out the win­dow

World of Animals - - Animal Clocks -

An­i­mals in the ex­treme north no longer fol­low cir­ca­dian rhythms due to the ab­nor­mal­ity of the light they re­ceive. Mid­win­ter brings round-the­clock dark­ness, and in sum­mer the Sun doesn’t set. While this hap­pens pre­dictably ev­ery year, daily rhythms get lost in the con­stant light con­di­tions. Po­lar an­i­mals can’t rely on reg­u­lar changes in light cues to dic­tate what time to get up and go back to sleep, so in­stead they have sim­ply given up fol­low­ing a body clock at all.

Rein­deer in north­ern Nor­way have been found to for­age around the clock and take short naps in be­tween graz­ing whether they are in blaz­ing sun­shine or com­plete dark­ness.

Know­ing the time of day may not be im­por­tant to rein­deer, but they still need to keep track of the sea­sons in or­der to syn­chro­nise the herd’s breed­ing to en­sure enough food avail­abil­ity for nurs­ing mothers. It’s still a mystery as to how rein­deer know when to re­pro­duce, but it’s pos­si­ble that fluc­tu­a­tions in the sleep hor­mone mela­tonin kick in dur­ing au­tumn and spring.

Sun­rays

Arc­tic rein­deer mainly eat lichen and moss, but they are also known to feed on lem­mings, Arc­tic char fish and eggs

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