Penguins
Penguins are flightless marine birds that live in the Southern Hemisphere, mainly in the Antarctic and Subantarctic regions. Penguins are a unique group, highly specialized and adapted to the marine environment and harsh polar climate in which they live. Of course, they are cute and energetic, and they are a lovable group of birds.
In a large sea of churning bubbles and diving figures of the same kind, king penguins pursue their prey with all their strength. This species is known for its excellent deep-water diving abilities.
The Portuguese navigators Vasco da Gama and Ferdinand Magellan were the first to describe penguins during their expeditions (1497-1498 and 1519-1522 respectively). The two discovered South African penguins and South American penguins respectively. However, most penguin species were not gradually known to the world until the 18th century, when humans explored the Southern Ocean in search of the Antarctic continent.
"Penguin-style" diving
Penguins are probably the birds most adapted to life in the ocean. People have studied their swimming and diving abilities for decades, and accumulated detailed information.
Although it was once widely rumored that the swimming speed of penguins was as high as 60 kilometers/hour, after accurate calculations of emperor penguins, Adélie penguins and South African penguins, their normal swimming speed is 5 to 10 kilometers/hour. Of course, The speed will undoubtedly be faster during temporary sudden acceleration, especially when doing the " dolphin style T-stroke" (a swimming movement in which penguins temporarily jump out of the water). The purpose of penguins doing the "dolphin-style T-swim" is unclear. Maybe it's to confuse the sight of underwater predators, maybe it's jumping into the air to reduce resistance and speed up, or maybe it's to breathe without affecting speed. go ahead.
The diving behavior of several penguin species has been studied using pressure-sensitive depth recorders. The duration of diving varies greatly between different species: white-browed penguins, striped-cheeked penguins and long-browed penguins usually only last 0.5 to 1.5 minutes and rarely exceed 2 minutes; while South African penguins and emperor penguins average 2.5 minutes, among which South African penguins It can last up to 5 minutes, and for emperor penguins, it can last more than 18 minutes. Diving depth also varies greatly within and between species, ranging from 45 meters to an astonishing 530 meters in the case of emperor penguins. In a study of king penguin diving, half of them could dive below 50 meters, and 2 dived below 240 meters. On the contrary, studies of striped-cheeked penguins show that 90% do not exceed 45 meters, and 40% of them are less than 10 meters, despite the fact that they can dive to depths of 100 meters. Similarly, 85% of white-browed penguins are less than 20 meters tall. The diving depth range of Adélie penguins is 20 to 170 meters.
How do these relatively small animals manage to dive into deep water so frequently? Diving mode is mainly affected by three major factors: first, the dive time, which depends on how long you can hold your breath; second, the ability to withstand increasing pressure with water depth; and third, the ability to regulate temperature and minimize heat loss. Among them, the time of holding your breath is determined by the body's storage of oxygen. Adélie penguins consume 100 milliliters of oxygen per minute when resting. At this rate, it will use up all the oxygen in its body in 2.5 minutes of diving. But in fact, during diving, the muscles can still function normally even though the supply of blood and oxygen is greatly reduced; and the heart rate drops from 80 to 100 beats per minute at rest to 20 beats, thus causing the same body The oxygen content can be maintained for 5 to 6 minutes of diving.
Humans dive by breathing compressed air, which is often prone to coma due to inert gases, as well as the so-called "altitude sickness." But if you use breath-hold diving, the inert gas will be very limited and the risk will be greatly reduced. Short, shallow dives are not a problem for penguins. The key is how emperor and king penguins can dive into deep water for a long time? It remains a mystery to this day.
Penguins seem to be very adaptable to reducing heat dissipation when diving.However, the reason why their feathers are insulating is probably due to trapped air, and during diving, a considerable amount of this air is expelled from the back of the penguin in the form of a series of bubbles under the action of pressure. So penguins may need to stay active in cold water to stay warm.
Little is known about how penguins hunt underwater and how often. However, any animal that feeds on krill and similar crustaceans will prey on very small prey, usually less than 3 centimeters in length. It is estimated that a brooding striped-cheeked penguin dives for food an average of 191 times a day, and needs to catch 16 krill in each dive. In other words, it catches an average of 1 shrimp every 6 seconds. By comparison, king penguins typically dive 865 times a day, and they only need to spend an average of 10% of those dives to catch a squid or a fish to meet their target.
The type of prey also affects the length of the dive. Penguins that feed on relatively slow-moving, swarming crustaceans may be able to capture large amounts of food in a short period of time. Penguins that target fast-moving squid and fish need to stay underwater longer, but they only need a few hits to satisfy their appetites. This may be used to explain why South African penguins, which feed mainly on fish near the surface, dive much longer than white-browed penguins, which also dive shallowly but feed on krill.
Natural swimmers
Form and function
All species of penguins are very similar in structure and body feathers, but they differ greatly in body shape and weight. The feathers on their back are mainly blue-gray or blue-black, and their belly is basically white. Marks used to distinguish species, such as horns, crowns, face, neck stripes and chest stripes, are mainly concentrated on the head and upper chest. These features are easy to see when penguins swim on the surface of the water. The size of male penguins is usually slightly larger than that of female penguins, which is relatively more obvious in the genus Horned Penguin, but the appearance of the two sexes is very similar. The chicks are gray or brown all over, or the feathers on both sides of the back and lower layer are white. The body feathers of young birds are often close to those of adult birds, with only some minor differences in feathers and other aspects. The shape and structure of penguins are very suitable for marine life. They have streamlined bodies and powerful flippers to help them swim and dive. Their bodies are densely covered with 3 layers of short feathers. The wings degenerate into strong, tough, narrow flippers, allowing them to propel themselves quickly through the water.
Penguins have shorter feet and shins; their legs are very far back, and they work with their tails to control direction when diving. On land, penguins often stand on their heels, using their strong tail feathers for support. Because of their short legs, penguins appear to waddle when walking on land, but some species are able to use their bellies to glide quickly on ice. And, despite their seemingly inefficient pace, some species are capable of traveling long distances between their breeding grounds and the open ocean. Penguin skeletons are relatively heavy, and most species have skeletons that are only slightly lighter than water, thus reducing energy consumption during diving. The beak is short and strong, capable of grabbing food powerfully. The beaks of emperor penguins and king penguins are long and slightly curved, perhaps to adapt to hunting fast-swimming fish and squid in deep water.
