It’s so hot in Africa, how can elephants survive?

Large warm-blooded animals not only produce large amounts of internal heat, they also have a relatively small surface area to volume ratio. When the weather is hot, in order to maintain a constant body temperature, an elephant emits more heat per unit surface area than a person. The larger the elephant, the more heat it needs to dissipate. Moreover, elephants do not sweat, nor do they stick out their tongues and pant like dogs. So, what ability do elephants rely on to "walk around" in a hot environment?

One of the secrets of its heat resistance is its big ears, which act like a large radiator. A 1992 study showed that when the temperature is 20°C, a 2,000-kilogram African elephant can dissipate excess heat simply by flapping its ears. However, some African elephants can weigh up to 7,000 kilograms, and most of them live in an environment with a temperature of 40°C. At the same time, Asian elephants' ears are one-third the size of African elephants, so they can only dissipate one-third of the heat through their ears. In this case, it is not enough to dissipate heat through the ears alone.

The Weissenberg research team at the Austrian Veterinary University also discovered another secret of elephants' heat tolerance. They studied six African elephants at the Vienna Zoo. When the elephants open their mouths, drop the pills down their throats along with other treats. In fact, what is wrapped in the "pill" is not a medicine, but a temperature sensor and a radio transmitter. Using the pills, researchers obtained thermal images of elephants. Researchers found that when elephants lose heat, hot spots appear on their ears, legs and belly. When a certain part of the body is covered with a network of capillaries, a large amount of "hot blood" flows there, heating the skin and forming hot spots on the thermal imaging map. In other words, the place where hot spots appear is the heat dissipation area of ??the body.

The skin of all mammals is like a cooling vent. Through the skin, animals can dissipate excess heat to regulate body temperature. Elephants are the first mammals known to be able to open, close and fuse cooling vents. Weisenberg believes this allows elephants to precisely regulate their body temperature in moderate weather. Elephants only use this tactic when they feel comfortable and neither too cold nor too hot. Some researchers have even theorized that elephants have the ability to dissipate heat from a patch of skin to cool an organ.

Mammals have hair on their body surface. The hair layer can maintain a thin layer of air on the surface of the skin. This layer of air can reduce heat loss and have a thermal insulation effect. However, the elephant's hair is sparse and cannot play this role. So, what is the purpose of the hard, vertical hair on the elephant’s body?

By studying computer models, Myhrvold of Princeton University in the United States found that the sparse hair of elephants is not for thermal insulation, but serves as a "heat sink." Elephant hair can increase heat dissipation by 20%! He believes that elephant hair is not a relic of evolution and may have evolved to help elephants cool down.

However, even with so many ways to dissipate heat, elephants may still be unable to dissipate excess heat when encountering extremely hot weather. As a result, elephants evolved another cooling strategy. Weissenberg also had 17 Asian elephants in Germany and Thailand swallow "pills" and used temperature sensors to monitor the elephants' core temperatures. Experiments show that in Germany, when the temperature is 21°C, the elephant's core temperature fluctuates within a range of about 0.5°C. However, in Thailand, when the temperature is 30°C, the elephant's core temperature fluctuates by more than 1°C, from a minimum of 35.5°C at night to 38°C during the day!

Asian elephants improve their ability to withstand high temperatures during the day by lowering their body temperature at night

This is like experiencing a power outage in the summer. As long as an appropriate amount of ice is placed in the refrigerator, the temperature during the day will be lowered. High, the food in the refrigerator will not deteriorate due to the temperature of the refrigerator rising too quickly. This ability was once considered unique to desert mammals. For example, a camel's body temperature can rise from 34°C at night to over 41°C during the day!

As global warming intensifies, tropical areas where African elephants roam will become hotter. In these areas, the temperature rises more at night than during the day. This will make it more difficult for large animals like African elephants to maintain a suitable body temperature. The survival prospects of elephants are worrying. Scientists predict that under the "force" of the environment, African elephants will inevitably change some behavioral patterns, and their bodies will also undergo corresponding changes. Perhaps African elephants will eventually have to downsize to adapt to increasingly hotter conditions.

The original text comes from "Science Illustrated"

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