|Why are whales mammals and not fish?|
|Question Date: 2015-01-28|
Scientists group animals based on key traits or
characters that define them. Do you know
what some of those traits are for mammals? I
bet you do! Think about: warm blooded, make milk
for their babies, and have fur or hair... you can
look up the rest. Guess what? Whales have
those traits! Now think about fish - do they
need to breathe air? Nope - they have gills
that can filter oxygen from the water. But
whales have true lungs like yours - they have
to inhale a big gulp of air and hold their breath
when they go under water. Now of course their
lungs are bigger and shaped slightly different
than a person's, but they are still lungs. Here's
another question for you to think about (and I bet
you'll figure it out): is a bat a bird? Why or
So mammals are warm-blooded animals that have hair
and usually give live birth, rather than lay eggs.
Fish on the other hand, are cold-blooded and lay
eggs. So if an animal swims in the water, but
still gives live birth, it is probably a mammal
and not a fish. Whales are interesting because
they were fish a long time ago, then became a
wolf-like land creature, and then evolved back
into the water. So every sea mammal was once a
land mammal, but fish have never lived on land.
Wales give live birth, make milk, have a
three-bone inner ear, and breathe air. Fish do
none of these things, but mammals do all of them.
Therefore, whales are mammals.
Whales and fish are marine creatures but whales
are categorized as mammals because of certain
characteristics. Mammals are usually
endothermic, breathe with lunge, give birth to
live young, and have hair. Whales are endothermic
meaning they are warm-blooded, and their
internal temperature is maintained and doesn't
change based on their environment. They have to
come to the surface and breathe through their
blowholes, whereas fish use gills to breathe
and just remove oxygen from their bodies.
Whales give birth to live young whereas fish
lay eggs. Lastly, even though they aren't
covered in hair, they do have bristly hair around
some parts of their bodies. Even though whales
look like "big fish", they are completely
difference than fish and are categorized as
Whales are mammals even though they look like
fish. Whales, like other mammals are warm
blooded, meaning they keep their bodies warm.
Whales keep their body temperatures higher than
the water they swim in. Whales also give live
births. That means that their whales' babies are
miniature versions of the adult; they don't lay
eggs. The whales also feed their babies milk,
another characteristic of mammals. It is true
that most mammals usually have fur but whales
don't. But whales have most of the
characteristics of mammals, so they belong in that
Fish on the other hand, are cold blooded, lay eggs
(usually), don't produce milk, and have scales.
Click Here to return to the search form.
Copyright © 2020 The Regents of the University of California,
All Rights Reserved.