Why can the spotted geese fly over Mount Everest?

Spotted goose is an ordinary goose with a flat appearance.

The medium-sized striped goose has light gray feathers and two black stripes on the white back of the head. It is this conspicuous two bars, conspicuous two bars, which shows the unusual identity of the spotted geese. He is an excellent high-altitude pilot in the flock.

Every autumn, the spotted geese fly from Qinghai Lake, even further away in Mongolia, across the Himalayas to India for the winter. When spring comes, the striped geese once again cross the Himalayas, fly back to the north from the south, stay in the lake area with abundant water plants and raise geese.

When climbing mountains, the higher the altitude, the lower the oxygen content in the air. At an altitude of 6000 meters, the oxygen content is only half of the sea level. At 8844.43 meters of Mount Everest, the oxygen content in the air is only 1/3 of that at sea level.

. When you reach the 6000-meter mountain, you breathe in at one breath, and the amount of oxygen entering your body is only half as much as usual.

The higher the altitude, the lower the atmospheric pressure. When you breathe, the air pressure in your lungs is lower than the outside air pressure, so that air can enter the lungs. At high altitude, the air pressure is lower than that in plain areas. When inhaling, we must make greater efforts to expand the volume of the lungs and make them bigger, so that the air pressure in the lungs can be lower and air can be inhaled.

Breathing is a very difficult activity on high mountains. You consume more energy, but you inhale less oxygen. Birds are like you. When flying to the mountains, the striped geese are in a low-pressure and anoxic environment, and breathing needs a lot of energy. At this time, the striped geese should reserve enough energy, flap their wings and climb over the mountains.

On the one hand, it is an anoxic environment, on the other hand, it is a flying movement with huge oxygen consumption. How did the striped goose do it? The problem that has been puzzling for many years has recently been solved by biologists and physicists.

The path that the spotted geese flew over.

In the long migration journey of birds, energy consumption is huge, and the more labor-saving the flight, the more practical it is. For birds, low-energy flight has two key points: one is to control the flying height, and the higher the flight, the more laborious it is. At an altitude of 8000 meters, the minimum power required for flight is 50% higher than the sea level. Second, take the wind, that is, take advantage of the airflow and take a ride.

The journey of striped geese across the Himalayas is very difficult. Does it fly according to the main points of energy saving? The biotechnology research team installed GPS locators on 965,438+0 wild geese in India, Qinghai Lake in China and Mongolia, observed their migration twice a year, and recorded goose data for more than 400 days.

In autumn, the southern tour lasted 8 1 day, migrated 3 152 km, and the highest flying altitude reached 7290 meters. In spring, the trip to the north, the average time of striped geese is 47 days, the journey is more than 3000 kilometers, and the highest flying height reaches 6540 meters. Although the highest flying height is more than 7000 meters, the flying time of striped goose at more than 6000 meters is very short. 95% of the time, the spotted geese fly below 5489 meters.

The picture above is a map of the flying of striped geese. In the picture, the colored line is the actual path of the wild goose, the white line is the shortest path, and the white cross is several peaks in the Himalayas at an altitude of more than 8000 meters. The actual flying distance of the geese is longer than the shortest path by112km, leaning to the east of the Qinghai-Tibet Plateau and bypassing the highest peak.

Spotted geese choose to fly along the valley and try to reduce their height. Although they have the ability to fly high, they won't go beyond the top of the mountain. Bar-headed geese have achieved the first goal of long-distance migration to save energy and control flying height.

Did the striped goose do the second thing to save energy: ride the wind? Not exactly.

In mountainous areas, the dominant wind during the day is the valley wind, which blows from the foot of the mountain to the top of the mountain. The dominant wind at night is the mountain wind, which blows from the top of the mountain to the bottom. Spotted geese usually fly at night and early in the morning. When it went uphill, it met with a headwind descending from the top of the mountain.

In the journey to the north, the biggest uphill journey is to cross the Himalayan barrier and enter the Qinghai-Tibet Plateau. When crossing the mountain barrier, the spotted geese choose the night when the wind is relaxed, rather than the day when the heat flow rises. From the foot of the mountain to the top of the mountain, the upward slope is very steep, while it takes only 8 hours for the spotted goose to cross the height difference of 5000 meters, and the upward speed is very fast, with the minimum climbing speed of 0.8 ~ 2.2 km/h.

Flying at night is more expensive than flying during the day, but the air flow at night is more stable and less turbulent than during the day. Nocturnal geese 1 day cross the Himalayas, which is the holder of the longest climbing flight record so far.

Without the help of the uphill wind, the striped goose flew over the Himalayas with its strong body and wings

The secret of striped goose's body

The ability of striped goose to climb up the hill against the wind and climb over mountains and mountains comes from its efficient metabolic rate. The striped geese have their own metabolic pattern in the anoxic environment, which supports them to fly freely in the sky.

The life range of striped geese is very broad, with the ground from south to north and the space from low to high. From the lake area at sea level, to the Qinghai-Tibet Plateau at 4000 meters, and then to the Himalayas at 6000 meters. Spotted geese can climb 6000 meters a day. In contrast, in one day, living in the plain, we can't live without oxygen. Within a day, Sherpas living in the plateau will feel dizzy and chest tightness when they come to the plain. Humans can't adapt to the dramatic changes in altitude in a short time, and striped geese easily solve this problem. Its secret lies in: there are two sets of metabolic models, the ordinary model is used in the plain; When flying high, reduce the metabolic rate and start the efficient mode.

The research team from the University of British Columbia in Canada conducted a wind tunnel test on the striped goose. Wind tunnel simulates the natural environment at different heights. Striped geese carry sensors on their backs and wear breathing masks to provide hypoxic air at different altitudes (5500 meters and 9000 meters above sea level). The research team collected the heartbeat, respiration, body temperature, blood oxygen and other data of the spotted geese flying at different altitudes for analysis. The test results show that it is not a legend that the striped goose flies over Mount Everest, but it can fly at an altitude of 9000 meters.

Artificial incubation, born and raised in the plain, without actual field training, the spotted geese can easily cope with flying at an altitude of 9000 meters in the test.

What's different from the usual geese? The two most shocking findings are that the heart rate remains unchanged and the body temperature drops.

1. Compared with normal flight, the heart rate of striped geese did not increase when flying under anoxic conditions. When you are short of oxygen, your heart will beat faster and faster to deliver insufficient oxygen to your body. However, even if the geese fly to the extreme height of 9000 meters, the heartbeat frequency has not accelerated, indicating that the geese's heart has not reached its maximum working capacity, and there is still room.

2. When flying high, the blood in the veins of striped geese will cool down, and the cooling temperature will exceed 2℃. When running, it gets hotter and hotter, while the striped goose is just the opposite. The more you fly, the colder your blood becomes. What are the benefits of cold blood? Hemoglobin carrying oxygen is very sensitive to temperature. With the increase of temperature, the ability of hemoglobin to bind oxygen decreases. Striped geese reduce blood temperature and improve the ability of hemoglobin to bind oxygen.

How can zebra geese ensure their own oxygen supply without speeding up their heart rate during hypoxia? When flying at high altitude, how can the striped goose reduce the blood temperature instead of dissipating heat during exercise? There is a unified answer to the two questions: striped geese reduce their metabolic rate during hypoxia. The metabolic rate of striped goose under hypoxia is much lower than that under normal conditions. Simply put, striped geese in anoxic mode can consume less energy and provide more exercise.

Under hypoxia, the basal metabolic rate at rest is lower than that in normal state, and the exercise metabolic rate during flight is lower than that during normal flight. In the absence of oxygen, striped geese will not only switch to the most efficient oxygen use mode during flight, but also use the most efficient oxygen use mode during rest. One way to reduce metabolic rate is to reduce relatively unimportant energy supply, such as digestion. For example, the striped goose will shrink the intestinal tissue before migration, reducing the energy needed for digestion.

On the plains with abundant oxygen, striped geese use a common metabolic model, and oxygen is used casually. At the altitude of hypoxia, striped geese use the low metabolism mode of saving electricity and use every part of oxygen on the blade. This is the secret of barrier-free switching of its living space.

One last question: How high can the spotted geese fly? Look at the picture. The above picture shows the venous oxygen partial pressure of striped goose. Black dots are normal, blue dots are moderately hypoxic, and red dots are highly hypoxic. Under the condition of high hypoxia, the venous blood oxygen value is also 25mmHg, which shows that striped goose has maintained its oxygen reserve at an altitude of 9000 meters and is not limited by oxygen. In other words, the spotted goose is not troubled by the thin oxygen of Mount Everest, and it still has the potential to fly higher.

The sky is high enough for birds to fly. Mount Everest is not the limit of the striped goose, but the sky is its destination.