Life Lines by Dr. Dolittle

Sponsored by the American Physiological Society

Hummingbirds can choose how deep to sleep

Photo of a purple-throated carib hummingbird by Charles J. Sharp via Wikimedia Commons.

Could you imagine drinking a can of soda every minute just to support your high metabolism? Amazingly, that is the equivalent to how much sugar a hummingbird needs to support their rapid wingbeats during flight. In fact, hummingbird flight muscles are the fastest on record, allowing the birds to flap their wings at a rate of up to 200 beats per second! That explains why they are always at my feeder.

You can see just how rapidly their wings beat in this video. Well, at least you can see the blur of their wings as they are beating…

Here they are in slow motion:

So, how do they get any sleep with such an insatiable appetite for sugar? To solve this problem, hummingbirds enter bouts of torpor during the night during which they reduce their body temperature and energy needs. Some species enter deep torpor during which they lower their body temperature to only 3 degrees C. This is a risky move as they are unable to respond to threats while in such a deep state of torpor. One the positive side, it may protect them from predators that can sense body heat, like snakes. Alternatively, hummingbirds may choose to only lower their temperature by about 1-20 degrees C to enable them to wake up quickly if necessary.

Having the flexibility to either drop into shallow or deep torpor is unique among hummingbirds. Of the 200 or so other species of birds and mammals that utilize torpor to save energy, body temperatures during torpor are typically species-specific and only implement one or the other strategy to reduce metabolism.

Sources

A Shankar, INH Cisneros, S Thompson, CH GRaham, DR Powers. A heterothermic spectrum in hummingbirds. Journal of Experimental Biology. 225(2): jeb243208, 2022.

American Scientist. Volume 110: 70-71, 2022.

Videos from YouTube

Categories: Diet and Exercise, Exercise, Extreme Animals, Hibernation and Hypoxia, Nature's Solutions, sleep

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