Film title: What is a mammal?

Many years ago, people thought that whales were very large fish.

After all, their bodies do have a similar shape.

But scientists then realised the behaviour of whales is different to fish, but the same as mammals.

Mammals

Fish breathe oxygen underwater through their gills.

gills

Whales must go to the surface to breathe in air through their blowholes.

blowholes

They don't have gills.

Just like other mammals. they breathe with lungs.

lungs

Most fish lay eggs to reproduce.

Whales give birth to live young, just like other mammals.

live young

Mother whales, called cows, suckle their young on milk produced by organs called mammary glands.

mammary glands

All mammal species have mammary glands.

Mammals are the only animals to have hair or fur.

fur

It's not very noticeable on whales, but they do have some hair bristles, usually on their heads.

Finally, it was discovered whales are warm-blooded.

warm-blooded

This means they can control their own body temperature.

These traits allowed scientists to conclude that whales aren't fish at all, but are in fact mammals.

lungs
live young
mammary glands
warm-blooded

Find out why we classify whales as mammals, not fish.

Learning points

• Mammals are one of the five types of vertebrates.
• Mammals give birth to live offspring, suckle their young with mammary glands, have hair or fur and are warm-blooded.

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