What Does It Mean to be Warm Blooded or Cold Blooded?

Animals are Either Warm Blooded or Cold Blooded.

By Moira Whitehouse PhD

The body temperature of a warm blooded animal stays about the same no matter how cold or hot it is outside.

Being warm blooded

On a sunny, hot day a warm blooded animals’ body temperature is the same as it is on a cold, snowy day .

Warm blooded animals also have special ways to keep their bodies from getting too warm.

A warm blooded animal manages this by using (burning) the food it eats for energy to keep its body warm.

Birds and Mammals are warm blooded, and so are we. Our body temperature stays about 98.6 degrees F when we are healthy. If our temperature gets much above or below that, it might be a clue that we are getting sick.

For example, while playing outside on a hot 108°Texas day, your temperature would be about 98.6 degrees F.

And even while making a snowman on a very cold day, your temperature would still remain the same -- about 98.6 degrees F.

Bears are warm blooded mammals like us. Their body temperature stays at about 90 degrees F in both cold or hot weather (except when they are hibernating).

Other warm blooded animals also have body temperatures that remain constant regardless of the outside temperature.

Dogs and cats temperatures vary between 100.5 and 102.5 degrees F.

A whale’s temperature stays at about 98.6 degrees F in icy cold water and in warm tropical water as well.

A bird’s temperature is always about 105 degrees F no matter where it lives-- in the cold Arctic or the hot rain forest.

All animals change some of what they eat into mechanical energy used for movement.

animals also use some of their food to create heat for keeping their temperature constant.

Warm blooded

The body temperature of cold blooded animals, such as reptiles, amphibians, and fish, becomes warmer or cooler as the temperature around them changes.

Being cold blooded

On a cold winter night, their body temperature falls.

On a hot day in the summer, their body temperature goes up.

A frog is an amphibian, and therefore is cold blooded. His body temperature is about the same as his surroundings. If it is 40 degrees F outside, his body temperature is about 40 degrees F and if it is 95 degrees F outside, his body temperature is about 95 degrees F.

In hot environments, the temperature of a cold-blooded animal could be warmer than the temperature of a warm-blooded animal. Cold-blooded animals are much more active in warm environments but they are very slow moving and sluggish in cold environments

So that we can see the difference in warm and cold blooded animals we will use an infrared light, like this one, to view a warm blooded person and a cold blooded animal.

Cool objects show up as cooler colors: blues, greens and blacks.

On the next slide you will observe infrared photos of a person holding a cold blooded lizard. Notice the the colors of the lizard and frog images and compare them to the image of warm blooded human holding them.

In infrared light, warm objects show up as warm colors: reds, oranges and yellows.

Both the frog and gecko appear as a darker color than the human. That means their body temperature is colder than the human’s. This is because they are cold blooded and would be the same temperature as the room, whereas the human’s temperature is always warm.

Here we see a the hand of a child as he plays with a pet snake. It is pretty easy to see which is warm and which is cold blooded.

Notice how his body temperature rises as he basks in the sun. (Compare picture 1 and 2)

This lizard has moved into the sunlight to get warm.

Just as he moves into the sunlight

After he sits in the sunlight for a few minutes

Turtles are reptiles and are cold-blooded. They spend much of their lives in water and will bask in the sun on warm days. When the weather turns cold, turtles will often burrow into the soil until warm weather returns.

These turtles have just walked out of pool of cool water. Notice how cold they still are.

Notice how warm this turtle has become after basking in the sun!

From our study of animal needs, we might remember one of a warm-blooded animal’s needs is to keep its body at a certain temperature.

If the body temperature gets too high or low, an organism will likely be sick and may even die.

If your temperature is higher than 100 degrees F or lower than 93 degrees F, it probably means that you are sick.

Temperature too high

Or too low

The range of body temperatures for a cold-blooded animal is much greater than for a warm-blooded animal.

However, if their temperature gets outside of that range, too hot or too cold, they will also die.

So the body temperature of an animal in either group, warm or cold-blooded, has to stay within a certain range.

First, we will look at how warm blooded animals stay cool when the temperature outside gets above their comfort level.

But how do they manage that, how do they keep warm or cool?

One of an animal’s basic needs is to keep its body in the right temperature range.

How an animal keeps its temperature at the right level mainly depends on whether it is warm or cold-blooded.

To cool off many warm-blooded animals use the process of evaporating water.When water evaporates from the animal’s body it absorbs heat energy and cools the animal’s body.This is why you feel so cold when you get out of the swimming pool on a hot summer’s day.

One way warm blooded animals keep their bodies at a constant temperature in hot weather is by panting. Fast moving air over the animal’s tongue evaporates water cooling the tongue and the animal.

Animals like pigs wallow in mud when they are hot. The water evaporates and lowers the pig’s body temperature.

Some mammals sweat when they get too hot. Primates, such as humans, apes and monkey, have sweat glands all over their bodies. Dogs and cats have sweat glands only on their feet.

How would sweating cool an animal?

bead of sweat

Mammals who live in water like whales don’t need sweat glands. To cool off, they simply swim to a cooler spot in the ocean.

Many mammals and birds that live in hot climates avoid the summer heat by coming out to look for food at night when it is cooler. These animals are called nocturnal.

Big cats such as jaguars and cheetahs are nocturnal. They keep cool by lounging in the daytime and hunting at night. During the day, they rest under the shade of a big tree.

Some mammals who live in hot climates lose heat through their big ears.

Even Sooty Tern chicks know to get in the shade of a bigger bird (a Black Footed Albatross) when it gets too hot.

Like cats and dogs, birds also pant to get rid body heat. But it is not through evaporation that they lose heat. They breathe very quickly, letting the cooler air pass through their lungs which carries heat away from their bodies. A bird standing with its mouth open on a hot day is probably panting.

Now let’s consider how warm blooded animals keep warm when it is cold outside.

So mammals and birds, the two groups of warm blooded animals, have many different ways to keep cool. Can you remember some of them?

Land mammals that live in cold places often grow a thick layer hair or fur during the winter that keeps the heat inside their bodies. Their fur or hair acts like a blanket.

In the summer when the weather warms up, these animals lose that thick layer of hair or fur.

Whales and walruses live in cold ocean water and have a layer of blubber (fat) to keep them warm.

whale blubber

A polar bear has both a thick fur coat and a layer of blubber (fat) which insulate its body.

A bird’s feathers, like the mammal’s hair and fur, provide remarkable insulation from the cold. Many birds grow extra feathers in the fall to keep them warmer in the winter. They lose this feathers come spring.

Some birds cannot survive cold winter weather. These species migrate to locations with warmer temperatures and more food.

bird migration routes

Some warm blooded mammals such as ground squirrels, bears and bats cope with the cold by hibernating, a deep winter sleep.

In the fall, these animals eat a lot of food which they store as fat.

When cold weather comes mammals that hibernate find shelter in places such as holes in rocks or caves. When hibernating, the animal’s body temperature drops, and both its heartbeat and breathing slow down. It uses hardly any energy to stay alive.

This is when the animal lives off the stored fat that was packed on in the fall.

Some mammals and birds that live in very cold climates huddle together to keep themselves warm.

But what about cold-blooded animals?

So far we have talked about how warm-blooded animals keep themselves warm when their environment is cold and cool when it is hot.

What do you remember about cold-blooded animals and how they are different from warm-blooded animals?

To warm or cool their bodies, they must change their surroundings.

Cold blooded animals, you should remember, have a body temperature that is the same as the temperature in their surroundings.

Reptiles like lizards, turtles and crocodiles bask in the sun to warm up . After a cool night, lizards, turtles and snakes climb on to a rock or log where they lie in the sun which warms up their body.

When the day warms up and a reptile becomes too warm and needs to lower its body temperature, it finds a shady area under a rocks to cool down or log or slips into the cooler water.

Reptiles like lizards and snakes that live in the hot desert stay in underground burrows during the hot summer days coming out at night to hunt for food when it is cooler.

l

Amphibians like frogs and toads use the same techniques to warm up and cool down.In the spring and summer they lie on the bank of a lake or river absorbing the rays of the Sun thereby warming up their bodies.When they need to cool down, they slip into the cool water.

They may also simply swim into the warmer top layer of water in a pond toheat themselves up a bit. When they gettoo hot, they typically move to a cooler place, sometimes even going underground.

Generally during the winter, they burrow underground and hibernate below the level that the ground freezes. Their heart rate and breathing slow down. When spring comes they emerge.

But how do reptiles and amphibians stay warm in places where the temperature drops below freezing during the winter time.

Here we see where snakes and lizards have gone underground into burrows or caves to keep away from the freezing temperatures.

Thousands of Red sided garter snakes enter limestone caves to seek shelter below the frost line in an area that can experience harsh winter weather. This is the largest gathering of snakes anywhere in the world.

One amazing hibernation story is the Garter Snakes of Manitoba, Canada.

When the cold weather comes during winter, frogs, toads, and river turtles bury themselves in mud or soil and “hibernate”. In the spring when the sun warms the mud, out they come to absorb the heat of the Sun.

Some frogs that live in very cold places can’t dig down far enough into the soil to avoid the ice and actually freeze during the cold winter months.When the weather gets warmer, the frog’s body melts and after some repairs to its body comes alive.

Frozen frog

Fish who live in areas where the winters are cold move to deeper waters during the colder months or migrate to warmer waters.

What about the other cold blooded group of animals—fish?

For fish it is easy—they just swim to a layer of the water where the temperature is right for them.

So remember that if an animal is to survive, it must keep its body within a certain range of temperatures.

If its body temperature becomes too high or too low, an animal will become sick or die.

In this presentation we have discussed the following points:

• The differences between warm and cold-blooded animals.• How warm-blooded animals keep warm when it is cold outside.• How warm-blooded animals cool down when it is hot outside.• How cold-blooded animals warm up when it is cold outside.• How cold-blooded animals cool downwhen it is hot outside.• How cold-blooded animals survive cold winter temperatures.

Let’s go back over each point and see what you can remember.

What is the difference between a warm and cold blooded animal?

What two animal groups are warm blooded and which three are cold-blooded?

• How do warm-blooded animals (mammals and birds) keep warm when it is cold outside?

• How do warm-blooded animals (mammals and birds) cool down when it is hot outside?

• How do cold-blooded animals warm up when it is cold outside? Cold-blooded animals include reptiles such as turtles, lizards, snakes, crocodiles and alligators, amphibians such as frogs and toads and fish.

• How do cold-blooded animals cool downwhen it is hot outside?

(Cold-blooded animals include reptiles such as turtles, lizards, snakes, crocodiles and alligators, amphibians such as frogs and toads and fish.)

• And lastly, how do cold-blooded animals survive cold winter temperatures?

Stay cool! Bye!

(or maybe warm!)