Animals in hot deserts and the tropics need to lose heat and avoid gaining it, often while also conserving water.Anatomical
• Large surface area to volume ratio. Long, thin limbs and large ears increase the area from which heat can be lost. The fennec fox and the African elephant have very large ears with many blood vessels near the surface. Elephants flap their ears, which increases heat loss by convection.
• Thin or light-coloured coats. Less insulation lets heat escape, while pale fur reflects radiation from the Sun. Camels have thick fur on the back that shields the body from the Sun's radiation.
• Fat stored in one place, such as the camel's hump, rather than as a layer under the skin, so it does not insulate the rest of the body.Physiological
• Tolerating a rise in body temperature. A camel lets its core temperature rise by several degrees during the day (to about 40 °C) and loses the stored heat at night, when the air is cool. This means it does not have to sweat so much, saving water.
• Sweating and panting, which work well in dry air but use water.
• A low metabolic rate in some desert animals, producing less heat.Behavioural adaptations, such as being nocturnal or living in burrows, are also very important and are covered later.Some animals also protect the brain from overheating, which is the subject of the next lesson.
• Large surface area to volume ratio. Long, thin limbs and large ears increase the area from which heat can be lost. The fennec fox and the African elephant have very large ears with many blood vessels near the surface. Elephants flap their ears, which increases heat loss by convection.
• Thin or light-coloured coats. Less insulation lets heat escape, while pale fur reflects radiation from the Sun. Camels have thick fur on the back that shields the body from the Sun's radiation.
• Fat stored in one place, such as the camel's hump, rather than as a layer under the skin, so it does not insulate the rest of the body.Physiological
• Tolerating a rise in body temperature. A camel lets its core temperature rise by several degrees during the day (to about 40 °C) and loses the stored heat at night, when the air is cool. This means it does not have to sweat so much, saving water.
• Sweating and panting, which work well in dry air but use water.
• A low metabolic rate in some desert animals, producing less heat.Behavioural adaptations, such as being nocturnal or living in burrows, are also very important and are covered later.Some animals also protect the brain from overheating, which is the subject of the next lesson.