Scientists Say: Sanguivore

Sanguivore (noun, “SANG-wi-vor”)

A sanguivore is an animal that eats blood.

Some species survive on blood alone. They are called obligate sanguivores. Bedbugs, ticks and vampire bats are examples.

Other species drink blood to supplement their diet. Or they drink blood only at certain stages of their life. Part-time blood drinkers are called facultative sanguivores.

Consider mosquitoes. They usually eat plant nectar. But female mosquitoes need the protein in blood to help them mature their eggs.

Oxpeckers are another example of part-time vampires. These birds perch atop grazing rhinos and zebras in the African savannah and pluck ticks from the animals’ hides. They also lap up blood at the wound site where the tick was. Sometimes these birds pick open old wounds on the animal’s hide for an extra blood snack.

Blood doesn’t have many nutrients and packs few calories. It consists mostly of water. Most foods contain easy-to-digest sugars and fats. But blood doesn’t contain much of either. Instead, most of blood’s calories come from proteins, which are harder to digest. Blood also comes loaded with iron. Animals need some iron in their diet. But the high levels found in blood can be toxic.

Animals that eat blood must handle these dietary challenges. Take vampire bats. The three species of them are the only known mammals that are obligate sanguivores. Specialized kidneys let vampire bats purge water quickly. In fact, they usually begin peeing while they eat. Their digestive systems absorb very little iron from their food. And their guts also host microbes that help them break down blood proteins. These microbes also create vitamins that the bats cannot get from blood.

In a sentence

The poor nutritional quality of blood probably explains why humans never evolved to drink it.

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