Give reason- Dogs generally hang out their tongue in summer.
Hint: Dogs have high body temperature. Dogs also have fewer sweat glands to sweat and regulate the body temperature.
Complete answer: Dogs generally hang out their tongue in summer as in summers the temperature is very high. Hence to regulate the body temperature dogs hand out their tongue. An extended tongue acts as a radiator and tongue blood vessels dilate to increase the surface area for heat disposal. The main reason is that dogs cool themselves by hanging their tongue. This helps them to bring back their normal body temperature. Panting helps them to cool down. As the sweat glands are very less or absent in dogs, their body mechanism is routed to panting to regulate body temperature. If we compare this in content with humans. As humans have sweat glands, so they can perspire. Dogs don’t have sweat glands and cannot eliminate water. That is why humans perspire to eliminate water through skin to regulate body temperature. More the heat, the more we sweat to lower the temperature. So dogs must hang their tongue out to keep cool in summer. The evaporating saliva cools the blood that is passing through the tongue and mouth.
Note: The normal color of healthy tongue should be deep pink. It turns red due to heat or hot temperature. Due to excess increase of blood flow in the blood vessels of the tongue, it may bleed. This increased blood flow can lead to tongue injuries.