Nerdy Science Blog

The giraffe (Giraffa camilopardalis) is the tallest land animal in the world. Interestingly, it is also one of few animals which require minimal amounts of sleep (average 1.9 hours of total sleep time a day, compared to 7.75 hours for a human according to sources for BBC). Scientists have observed that giraffes sleep in short naps at nights, and usually sleep while standing (an ability shared by other ungulates, or hoofed animals). They rest their long necks on their hind legs, thus arching their long necks over their backs. They may also rest with their necks down at nights. When entering the phase of REM sleep (Rapid Eye Movement), giraffes must lie down on the ground (in a state of recumbency) to prevent from collapsing, as REM sleep causes muscular atony.
The sleeping behavior of eight giraffes in captivity at a zoo was observed for 152 nights by by Tobler and Schwierin (2003), and it was found that their timing for sleep is fragmented. The giraffes slept in intervals of 6 – 35 minutes, with older giraffes sleeping more while standing than lying down. If they had napped in the day, the giraffes showed an increase in sleeping while standing at nights. Their main sleeping hours were between 2000 and 0700 hours. Their daily total sleeping times were also quite constant, and not dependent on the age of the giraffes.
References:
Tobler, I. and Schwierin, B. (2003). Behavioural sleep in the giraffe (Giraffa camelopardalis) in a zoological garden. Journal of Sleep Research, 5 (1): 21 – 32.

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