Concentrating Blood Lightens Weight

three vampire bats sleep hanging upside down in what appears to be a cave

Biological Strategy

Vampire bat

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Capture, Absorb, or Filter Liquids

The most common liquid used by living systems is water, which they require to survive. But there are many other liquids that provide nourishment, play a role in defense mechanisms, or serve other purposes. Water varies in its availability; it is sometimes plentiful and sometimes very scarce or only available as fog or mist. To minimize the energy required to capture, absorb, or filter liquids, living systems have strategies that take advantage of the unique properties of the given liquid. For example, water moves from a gaseous to liquid state when it encounters a surface colder than the air. Plants in forests that experience fog and clouds more than rain have strategies that condense liquid water from moist air.

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Mammals

Class Mammalia (“breast”): Bats, cats, whales, horses, humans

Mammals make up less than 1% of all animals on earth, but they include some of the most well-known species. We know first-hand some of the characteristics that make mammals unique, like having hair, being able to sweat, and producing milk through mammary glands. Another critical shared feature is a set of highly-specialized teeth. Unlike sharks or alligators, for example, whose teeth are generally all the same size and shape, mammals have differently shaped teeth in different areas of the jaws to target specific foods or foraging strategies.

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The digestive and circulatory systems of vampire bats lighten their load after ingesting a large volume of blood by rapidly concentrating the blood and excreting the water content.

“[Bat] stomachs can hold a volume of blood equal to 57 percent of their body mass, but they can’t fly with this much extra weight. The problem is solved by rapidly getting rid of water and lightening their load before taking off. Within two minutes after a bat begins to feed, it begins to excrete a stream of very dilute urine.” (Crump 2005:68)

Crump, M. 2005. Headless Males Make Great Lovers & Other Unusual Natural Histories. University of Chicago Press, Chicago, IL. 199 pp.

Last Updated August 18, 2016

References

Book

Headless Males Make Great Lovers: And Other Unusual Natural Histories

01/05/2007 | Marty Crump

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