Eating colleagues with big mouths? Pelican, why do you stuff everything into your mouth?

Recently, a pelican in a theme park in Xi'an became a hot topic because of "eating a colleague". The pelican swallowed its "colleague" pigeon into its mouth , but fortunately the staff finally rescued the pigeon. This is not the first time that a pelican has been caught eating a "colleague". Ducklings and golden horned frogs have all been unable to escape the pelican's big mouth.

My colleague was arrested after taking a bite

Pelican, what else would you not dare to swallow!

No matter whether you can eat it or not, try it first

My mouth is big? Thanks, that's my throat pouch

Among the nearly 10,000 bird species alive today, the pelican genus, which consists of eight species, is not outstanding, but with their big beaks, pelicans are enough to become the most recognizable bird stars.

But are Pelicans really "big mouths"?

Strictly speaking, a bird's beak refers specifically to its upper and lower jaw bones and the keratin covering them. Based on this definition, the upper and lower jaws of the pelican are not particularly protruding - although they are very slender, slender upper and lower jaws are also common in cranes, ibises and storks. What really shapes the pelican's big beak is a "big pocket" attached to the lower jaw . This layer of blood-filled skin stretches from the tip of the lower jaw and even reaches the very bottom of the pelican's slender neck. This is their throat sac .

Australian pelican and its throat pouch | Paul Sunman / wikimedia

The throat pouch of a pink-backed pelican (Pelecanus rufescens), with blood vessels clearly visible | birdssoftheworld.org

During the long evolutionary process, the diverse shapes of bird beaks reflect their adaptation to their unique habitats. Many bird beaks have evolved to be extremely typical. For example, birds that feed on nuts generally have short, hard beaks, birds that feed on grass seeds have relatively small and nimble beaks, birds that forage on shallow mudflats often have long, thin beaks, and birds of prey mostly have sharp beaks that are easy to tear apart their prey. However, evolution does not have an "ultimate goal". Even birds with similar diets and habitats often have beaks of very different shapes due to different evolutionary paths. Pelicans are such an example.

As a bird that feeds on aquatic organisms, the ecological niche of pelicans is similar to that of boobies and gulls. However, when boobies swoop down from the air like arrows to attack schools of fish, pelicans choose another simpler and more brutal way of hunting. Most pelicans do not dive into the water. They just quietly wander on the water surface, and when the school of fish approaches, they suddenly shove their big mouths into the water . The smallest brown pelicans do have the habit of diving in the air to prey, but their hunting strategy after entering the water is similar to that of their peers, relying more on their big mouths to shove. Then, relying on the contractile throat sac and strong tongue muscles to squeeze together, the pelican squeezes water out of its mouth, and the fish and shrimp remain in the throat sac. This hunting strategy is somewhat similar to that of baleen whales.

Brown Pelican (Pelecanus occidentalis) fishing | birdsoftheworld.org

How to keep your mouth clean?

The throat sac plays a huge role in the process of hunting, but this structure is not perfect either - the water in the area where pelicans hunt is often turbid and full of mud and sand, and in the process of scooping up food, it is inevitable that some mud and sand will be swallowed. In addition, small fish struggling in the throat sac will inevitably drop some scales and debris, and sometimes multiple pelicans compete for food, and often catch each other's heads together, which often leads to debris in the throat sac .

This is harmless for baleen whales, but it is very different for pelicans - their nostrils are completely blocked by the glands used to expel salt, and their mouths are the only way to breathe .

Pelicans bite each other, with a mouth full of feathers - Dalmatian pelicans fighting for food | birdsoftheworld

Brown Pelicans use their throat pouches to hold branches for nesting | birdsoftheworld

For wild animals, keeping fresh breath is not important, but ensuring smooth breathing is a matter of life and death. Many people believe that pelicans will temporarily store leftover fish in their throat pouches, but this behavior has almost never been observed under natural conditions. They always swallow their prey as soon as possible after squeezing out the water. If the size of the prey exceeds the limit of the throat, the pelicans will spit it out decisively. These are all important measures to ensure that the trachea is not blocked . Of course, there are always unlucky people -

In 2015, the Field Museum in Illinois, USA, collected a dead American white pelican specimen. In its throat pouch was a huge freshwater drumfish (Aplodinotus grunniens). The fish was obviously larger than the limit of the pelican's throat, but the spines on the back of the fish got stuck in the pelican's upper jaw, making it unable to spit it out in time. The drumfish compressed the trachea, and the pelican suffocated to death.

In addition to such huge prey, the mud, fish scales and other debris in the water may also bring such serious consequences, which forces the pelican to keep its throat sac clean at all times. But without the help of its hands, it is not easy to clean the huge throat sac. It must use the help of its long curved neck to push the throat sac out of its lower jaw from the bottom . From a distance, this picture looks as scary as if it is spitting out its neck.

A brown pelican with its throat pouch exposed｜wikimedia

In fact, similar behavior is not exclusive to pelicans. The Internet-famous shoebill living in Africa often has similar behavior. This cute bird mainly feeds on lungfish in the wild. Its huge mouth swallows the mud and sand on the fish and even the weeds in the mudflats when it takes the lungfish out of the mud. The shoebill does not have a particularly obvious throat sac, and its breathing does not rely entirely on its mouth, but it is always uncomfortable to have a mouth full of mud. Using the neck to push the throat is also a common practice for them to keep their mouths clean .

Shoebill | biologydictionary.net

It is not only an amplifier, but also a siren.

In nature, the throat pouch is not a rare structure. But most animals do not need to clean it like pelicans do. For these creatures, the throat pouch does not participate in hunting at all, it is completely a structure used for sound or courtship .

The loud frog calls that disturb our sleep on midsummer nights are mostly due to the unique throat sacs of male frogs . As the most primitive animal group with throat structures, amphibians have true vocal cords, but the vocal cords alone cannot produce such a loud sound. The throat sacs on both sides or at the bottom of the oropharynx are the magic weapon unique to male frogs. The inflated air sacs resonate the sound emitted by the vocal cords, giving male frogs extremely loud courtship calls, while female frogs and all toads do not have this structure at all.

Unlike the throat pouches of male frogs that broadcast love, both sexes of siamangs (Symphalangus syndactylus), who live in stable monogamous relationships, have throat pouches, but from dawn to midday, shrill roars still roam the jungles of Sumatra and the Malay Peninsula - through a combination of several "monkey calls", siamangs convey to their neighbors that their territory is inviolable. In many cases, the calls are echoed by neighbors.

A crying siamang with its throat sac clearly visible | wikipedia

In frigatebirds , the throat sac is more like a silent show-off. The throat sac of male frigatebirds is brightly colored, and can be inflated into a huge ball. When the pelican shrinks the throat sac to the S-shaped neck during flight to reduce air resistance, the male frigatebirds flying and circling in the air with the huge "balloon". The bright colors reflect the male's sufficient nutritional intake, and the huge ball shape clearly conveys such a signal to the opposite sex - even with such a troublesome balloon hanging on my chest, I can still fly freely, my physique is great!

Lesser frigatebird (Fregata minor) | Jason Corriveau / wikimedia

From this perspective, pelicans have really maximized the role of their throat pouches. In addition to the practical function of foraging, their throat pouches still retain the function of courtship - during the breeding season, the color of the pelican's throat pouch and lower jaw will become more colorful. The huge throat pouch is what makes pelicans successful. Once upon a time, pelicans relied on this big mouth to eat all over the world. Except for Antarctica, they have opened their mouths in waters all over the world.

However, the throat pouch that made the pelicans successful has now become their new weak spot.

An American White Pelican with its throat pierced by a fishhook left on its prey | dailywildlifephoto.nathab.com

On March 11, 2017, in Henry County, Alabama, a strange American white pelican caught the attention of photographer Ken Hall: Unlike other pelicans he had photographed, the prey in this pelican's throat pouch seemed to be escaping - there seemed to be a hole on the underside of the throat pouch . This is not normal, many fish have sharp spines, but before they pierce the tough wall of the throat pouch, the pelican also has enough time to spit out the fish, but this pelican could only stare at the prey in pain and spent 10 minutes struggling to escape from the hole.

The fish is not the culprit for piercing the pelican's throat pouch, but the hook on the fish. Whether it is sports fishing or commercial longline fishing, it is common for fish to break free from the fishing line or even take the hook with them. When the pelican catches these dangerous prey, the sharp hook pierces the throat pouch. The pelican, who is in great pain, may have no other choice but to endure the wound that continues to expand as the prey twists.

Accidental injuries are just one of the disasters that pelicans are suffering. In April 2014, another pink-backed pelican was sent to the International Bird Rescue Research Center in Los Angeles. Its throat sac was also broken, but it was obviously not caused by an accident like a fish hook - the straight and thin wound was deliberately caused by a knife . After multiple surgeries and more than 300 stitches, this pelican recovered and returned to nature. However, as long as fishermen in some areas continue to regard pelicans as potential competitors for fishery resources, such intentional injury stories will not end.

Bird rescue workers sew up a pelican's throat pouch｜dailywildlifephoto.nathab.com

The recent trending pelicans swallowing their colleagues are certainly funny, but these pelicans are kept in small spaces. We have previously written about the "mini zoos" in shopping malls, which are not a suitable living environment for animals. In mini zoos, animals are often anxious and dull. I hope that everyone who likes animals will not visit such "mini zoos". And if you are a parent, "don't take your children to such zoos", as such zoos make it difficult for children to appreciate the beauty of life.

Author: A man is wandering

Editor: Zhu Buchong, Yellowtail Pollock