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How Do Kangaroos Survive Extreme Heat? | 20 Years of Planet Earth | BBC Earth - Video học tiếng Anh
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How Do Kangaroos Survive Extreme Heat? | 20 Years of Planet Earth | BBC Earth
How Do Kangaroos Survive Extreme Heat? | 20 Years of Planet Earth | BBC Earth
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0:00
Right now, while the sun is low,
0:03
there's no immediate cause for concern.
0:06
But this situation won't last long.
0:09
The sun's heat and the power to evaporate water
0:13
has had a profound effect on the bodies and habits
0:16
of everything that lives here.
0:22
This sun, potentially, is a killer…
0:27
..and the red kangaroos must acknowledge that.
0:32
Right now, while the sun is low,
0:34
there's no immediate cause for concern.
0:38
But this situation won't last long.
0:42
Australia is the world's most arid continent,
0:45
with blistering daytime temperatures.
0:55
Every hour, the temperature rises by five degrees centigrade.
1:07
Soon, the heat will reach a critical point.
1:20
Any kangaroo out in the open
1:22
is in serious danger of overheating.
1:31
In the full sun,
1:33
the temperature on the ground soars to 70 degrees.
1:42
By midday, the radiation is so intense, they must take shelter.
2:07
In the shade, they're shielded from much of the sun's energy,
2:10
but their body temperature can still rise.
2:16
So they lick saliva on to their forearms,
2:19
where there is a network of blood vessels close to the surface of the skin,
2:23
and as the saliva evaporates, their blood is cooled.
2:30
This thermal image shows just how effective the process is.
2:35
The blue areas on the body are the cooler parts.
2:47
As the saliva dries, it has to be replaced,
2:51
and this is a real drain on the kangaroo's body fluids.
3:05
Even in the shade, the earth is baking hot.
3:09
So the kangaroos dig away the warmed topsoil
3:13
to get at the cooler ground beneath.
3:38
By staying in the shade
3:39
and licking to control their body temperature,
3:42
kangaroos manage to get through the hottest part of the day without heatstroke.
3:48
But for the majority of desert animals,
3:50
this strategy would not be enough for survival.
