Even the world's greatest scorching sun survival experts have to race against time to survive.
Written by | Huw Cordey
Translate | Wang Le
Winds may bring abundant rainfall to the Amazon basin, but they have not spread this luck to every corner of the planet. One-third of the Earth's land is desert, and these places receive less than 50 millimeters of rainfall per year, often evaporating far more than rainfall.
The Sahara Desert is the most famous desert in the world, with an area of about 9.66 million square kilometers, making it the largest desert in the world. The Sahara Desert was formed under the influence of atmospheric circulation, a powerful global weather system. This process begins when warm, moist air rises above the equator; Warm, moist air cools down as it rises. Cold air can't retain as much moisture as warm air, so this moisture is released in the form of rain, which is why there are rainforests on both sides of the equator. As the air cools up, its density will increase, the temperature will become lower and lower, and the moisture will become less and less, and this cold air will spread from the equator to the north and south, and eventually descend back to the earth. After that, the dry air flows back to the equator, restarting the process. This air circulation is named after British meteorologist George Hardley and is known as the Hadley Circulation. It is the Hadley gyre that creates subtropical deserts on Earth, such as the Sahara.
Barren desert
Deserts also form in continental centers, such as those between China and Mongolia, and deserts form inland because clouds blowing from the coast tend to lose moisture before reaching these places. There are also deserts along the coast, such as the Atacama Desert in Chile, due to weak evaporation above cold ocean currents, resulting in dry air. Rain shadows can also form deserts, such as Death Valley in California, USA.
Despite the extreme environment of the desert, many animals still live here. They must adapt to life with little or no water, and learn to "live in harmony" with the extreme weather of the desert.
Extraordinary frog
In this water-scarce place, you'll find an animal that you might not expect – the frog. In fact, there are frogs in many deserts, except for the polar deserts in Antarctica. One of the strangest and cutest is the desert rain frog that lives in the arid regions of southern Africa. Like most small desert dwellers, it implements strict sun and heat protection strategies, spending most of the day in underground sand caves and only going out at night when it is suitable for foraging.
Desert rain frog
This rain frog is shaped and sized like a marshmallow. Its legs are short and thick, and its spherical body has paddle-like feet, which can be described as a natural cave animal. But that also means it can't jump, it crawls on the sand and keeps an eye out for its favorite food, termites. About 79% of the body of these small insects is water, which both fills and hydrates desert rain frogs. Of course, the premise is that the desert rain frog can really send 1 termite into its mouth. The desert rain frog is not a very agile predator, and it has to launch several attacks to catch termites. When it finally succeeds in catching termites, the desert rain frog must close its eyes, contract its eyeballs and push the food down to swallow it. This rain frog is really interesting everywhere.
The desert rain frog burrows out of the sand at night in search of its favorite food, termites
Termites are an important source of water for desert rain frogs, but termites alone cannot meet all the water needs of desert rain frogs. Their coastal desert home, although rainfall is scarce, has a relatively reliable source of moisture – fog. At night, cold air blows from the sea, creating a thick fog that envelops the desert. The night fog condenses on the vegetation, gathering into water droplets that fall into the sand. This is how the desert rain frog rehydrates – not by drinking water, but by absorbing water from the sand through its skin, perhaps with the help of its unique "belly absorbent zone", where their abdomen sticks to the sand when they are stationary. This piece of skin has no pigment distribution, is translucent, and has dense blood vessels. Scientists believe the area acts like blotting paper, helping desert rain frogs draw moisture from the moist sand. Desert rain frogs rely so much on this source of water that they live in fog for at least 100 days a year.
Desert rain frog in mating
On foggy nights, desert rain frogs appear one after another on the dunes, and females take this opportunity to find mates. The courtship calls of male frogs are not at all like frogs, and they do not croak. Instead, the male will make a low, mournful cry to announce his existence. If the female frog shows interest in the petite male, the male frog sticks to her back, and the female then swings through the sand back to her burrow. The male frog's legs are small and short, and only by doing so that he will not be left behind. (Desert rain frogs do not breed on open water.) In fact, desert rain frogs do not swim at all and will drown when they fall into the water. The male will cling to the female and burrow with her under the sand to lay eggs so they can stay away from the scorching desert sun. Females hold on to their eggs until they become frogs, a process that does not require passing through the tadpole stage.
During drought, Australia's ze burrowing toad can hide in the molting skin of underground cocoons to avoid dehydration
Some desert frogs are top underground survivors. Before the best time to breed, Australian water storage frogs can sting underground for many years, entering a dormant state similar to hibernation. This water storage frog does need stagnant water to lay eggs, but water is so rare in the desert that they must be prepared for the long term. To prevent water loss, they shrink their bodies and wrap themselves up in several layers of skin, exposing only their nostrils. As the name suggests, water storage frogs store water in their bodies (especially in their body tissues and bladder), which allows them to stay underground for up to 5 years. Indigenous Australians living in inland deserts sometimes use this water storage capacity – squeezing the storage frog to get a sip of drinking water.
Desert Fighter
Located in the heart of Asia, the Gobi Desert covers southern Mongolia and northern China, and is the fifth largest desert in the world, with a total area of about 1.3 million square kilometers. People think that the Gobi Desert is a cold desert, and that's exactly what it deserves. In the middle of winter, the temperature in the Gobi Desert can drop to -40°C, accompanied by cold winds. But the cold is not all, because in midsummer, the temperature here can soar to 45°C. Only a few species survive in this extreme environment all year round, and wild Bactrian camels are one of them. They are bound to rank among the most tenacious animals on Earth.
Wild Bactrian camels have long been fully adapted to the harsh climate of this desert. Their body temperature can change by about 6 ° C, which is fatal to most other mammals (in contrast, humans can only accept a change in body temperature of 2 ~ 3 ° C). In addition, they can withstand significant water loss (up to 40% of body weight). However, if given the opportunity, wild Bactrian camels can drink hundreds of liters of water in one go. That's perhaps not the most impressive. The most amazing thing is that they can smell water tens of kilometers away. In a place where there is almost no water, this skill is really practical.
Wild Bactrian camels in the Gobi Desert
In summer, wild twin humps cannot be too far away from the water source, but in winter, they can travel long distances. The journey of the wild twin humps does span thousands of kilometers. During this time, they still need to drink water. However, the summer puddles have been frozen, so they must rely on another source of water, snowfall from Siberia. Where the snow will fall is an unpredictable thing, and it may not persist for long. The snow does not melt (it is too cold to melt), but sublimation occurs. In dry air, snow evaporates directly without passing through the liquid phase. Therefore, in order to get the water it needs in winter, the camel must find the snow and eat it.
Wild Bactrian camels are experts at long journeys, sniffing out water sources tens of kilometers away
For some animals, gasping for air may be an effective way to cool down, but in a place where there is hardly any moisture, it is definitely not a good method. Therefore, the wild twin humps never gasp violently. In addition, the wild twin hump has another very useful "tool", and that is its hump. Contrary to popular belief, camel humps do not hold water. In fact, the hump stores a lot of fat, which provides the necessary energy guarantee for camels to travel long distances in the desert. This is the survival strategy of the wild Bactrian camels of the Gobi in the wild.
Wild Bactrian camels rely on snow for water
Survive in the scorching sun
Although the equatorial region receives the most concentrated amount of sunshine each year, the hottest places on Earth are not here, but in the tropics north and south of the equator, where less than 50 mm of rainfall is received annually. The warm, dry air rising from the equator (the temperature of the gas rises 10°C after the air rises from the rainforest) continues to erode this barren land.
Silver-covered Saharan silver ants
Due to the scarcity of rainfall, the vegetation here is naturally sparse. Without the shade of clouds and trees, the ground received intense solar radiation. The animals living here must not only adapt to life with little or no water, but also need to employ strategies to stay away from the heat. Sahara silver ants are worthy of the heat warriors - after all, no one can do such a crazy act as wandering around the desert at noon.
In order to survive the heat, Saharan silver ants use solar technology to prevent their bodies from overheating. Their bodies are covered with a special layer of glass-like hair that reflects sunlight, which is why they are silver. Sahara silver ants are also the fastest running ants in the world, and even relative to their size, the Sahara silver ants may be the fastest moving animals on the planet. They can move up to an astonishing speed of 85 centimeters per second. Recently, scientists have discovered that when silver ants run at this speed, they can leave the ground almost 6 legs at the same time and leap through the air. When the ground is hot enough to fry eggs, this is a fairly practical adaptation.
Warriors against the heat
However, despite these special qualities, Sahara silver ants can only last for a few minutes in such heat. A little longer it will suffer from heat stroke, just like the food it is searching for. Therefore, getting lost in the dunes would be disastrous. To avoid this, Saharan silver ants rotate every few seconds to determine the direction of the sun. When the time is up, it can go straight back to the safe nest. If a silver ant finds a victim that can be used as food, it drags it back to the underground nest. If the food is too large, other silver ants are needed to assist in transporting it or to divide it into small pieces. However, slaughter takes time, so Saharan silver ants need to weigh the risks and rewards of doing so – especially when they are already some distance away from their nest.
The whole process of foraging
So you see, even the Sahara silver ant, the world's greatest expert in sun survival, has to race against time to survive.
This article is excerpted with permission from BBC Perfect Planet (Jiangsu Phoenix Science and Technology Press, December 2022), and the title is added by the editor.
About the author
Huw Cordey is a well-known wildlife documentary producer. From 1996 to 2009, he worked for the Natural History Department of the BBC, producing documentaries such as "Land of the Tiger", "From the Andes to the Amazon", "Mammal Life", "Earth", "Diary of a Big Cat", "South Pacific" and so on. In 2009, Hugh Kordet began working as an independent producer, including Netflix's documentaries "Our Planet" and "Dances with Birds", and the Discovery Channel's natural history documentary series "North America".