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Right now, while the sun is low, there's no immediate cause for concern. But this situation won't last long. The sun's heat and the power to evaporate water has had a profound effect on the bodies and habits of everything that lives here. This sun, potentially, is a killer. And the red kangaroos must acknowledge that. Right now, while the sun is low, there's no immediate cause for concern. But this situation won't last long. Australia is the world's most arid continent with blistering daytime temperatures. Every hour, the temperature rises by 5° C.
Soon, the heat will reach a critical point. Any kangaroo out in the open is in serious danger of overheating. In the full sun, the temperature on the ground soars to 70°. By midday, the radiation is so intense they must take shelter. In the shade, they're shielded from much of the sun's energy, but their body temperature can still rise. So, they lick saliva onto their forearms, where there is a network of blood vessels close to the surface of the skin, and as the saliva evaporates, their blood is cooled. This thermal image shows just how effective the process is. The blue areas on the body are the cooler parts. As the saliva dries, it has to be
replaced, and this is a real drain on the kangaroo's body fluids. Even in the shade, the earth is baking hot. So, the kangaroos dig away the warmed topsoil to get at the cooler ground beneath. By staying in the shade and licking to control their body temperature, kangaroos manage to get through the hottest part of the day without heatstroke. But for the majority of desert animals, this strategy would not be enough for survival.
