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Regurgitation (digestion)

life science Maturity 7-9 Next article →

Regurgitation is the expulsion of material from the pharynx or the esophagus. The pharynx is part of the throat. The esophagus is the tube that carries food to the stomach. This process usually involves undigested food or blood.

Moorhen feeding chick
Moorhen feeding chick

While it may seem unpleasant, it is a normal and voluntary process for most animals. This makes it different from vomiting. Vomiting is a complex reflex the body uses to respond to toxins. For many species, regurgitation is a vital tool for survival and nutrition.

Many animals use this process to feed their offspring. This is common when young animals stay in a fixed location. Parents must forage or hunt for food elsewhere. Carrying small prey can be difficult because other predators might rob them. It is also hard to carry prey that is larger than a nest can hold.

20241201 eastern bluebird bolton notch sp PD205470
20241201 eastern bluebird bolton notch sp PD205470

Seabirds often use a regurgitative feeding strategy to solve these problems. They transport food internally to avoid theft by birds like skuas, gulls, or frigatebirds.

Different bird species have developed specific ways to manage this feeding. Many gulls have a subterminal spot near the end of their bill. This is an orange or red spot. Chicks peck this spot to stimulate the parent to regurgitate.

Moorhen feeding chick
Moorhen feeding chick

In some species, such as the blue-footed booby, masked booby, and Nazca booby, a brood hierarchy exists. This means the older chick is fed before the younger, subordinate chick. If food is scarce, siblicide may occur. This is when the dominant chick kills its sibling to keep all the resources.

Regurgitation also serves unique roles in digestion and food production. Ruminants use it as a normal part of their digestive cycle. During idle time, they bring up food known as cud. They chew this cud and swallow it again. This process reduces particle size and increases digestibility.

Flesh fly concentrating food
Flesh fly concentrating food

Honey bees also use regurgitation to produce honey. They store this honey in the beehive as a primary food source. Even insects like the flesh fly use it to concentrate nutrients. The fly regurgitates liquid food and holds it while evaporation occurs. This reduces the water content, leaving a much more concentrated meal.

In humans, the process can be voluntary or involuntary. It can occur alongside gastroesophageal reflux disease, also known as GERD. It can also happen with acid reflux or certain anatomical abnormalities.

20241201 eastern bluebird bolton notch sp PD205470
20241201 eastern bluebird bolton notch sp PD205470

For infants, spitting up is very common. Approximately 67% of 4-month-old infants spit up more than once per day. There is also a rare disorder called rumination syndrome. This involves the chronic, involuntary regurgitation of ingesta after eating. Some people can even control their muscles to regurgitate voluntarily. This is a skill sometimes seen in practitioners of yoga.

Specific biological effects can also arise from these feeding methods. Researchers found that the practice of regurgitation in certain penguins may cause metabolic alkalosis. This is a change in the body's chemical balance.

Moorhen feeding chick
Moorhen feeding chick

Some birds, like fulmars, use regurgitation as a defense mechanism when they feel threatened. This shows that the action can serve as protection rather than just nutrition. Professional regurgitators have even perfected the ability to use it for entertainment.

Regurgitation connects to many different biological systems and behaviors. It is a method of nutrient transport between generations. It is also a method of chemical processing in the digestive tract. Whether it is a bee making honey or a bird protecting its young, it is a highly effective strategy. It helps animals manage resources, avoid predators, and process complex foods. This simple movement of the throat is a key part of life in the natural world.

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File:Flesh fly concentrating food.jpg
Flesh fly concentrating food.jpg
File:Moorhen feeding chick.jpg
Moorhen feeding chick.jpg
File:20241201 eastern bluebird bolton notch sp PD205470.jpg
20241201 eastern bluebird bolton notch sp...
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