Which aquatic animal is not a fish

Why are whales and dolphins not fish?


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Why are whales and dolphins not fish?

Vivien from Meissen wanted to know why whales and dolphins are not fish. There are a few features that can be used to tell the differences between fish and mammals. Although whales and dolphins have body shapes similar to fish, they are mammals. We explain where the difference is here.

Dolphins and whales have body shapes similar to fish: they don't have legs, but fins, and their bodies are designed to move quickly in the water. At first glance, we might think that whales and dolphins belong to the biological class of fish.

A trout

However, the marine mammals are distinguished from these by important characteristics:

1. Fish breathe with their gills, whales and dolphins breathe with their lungs, just like us humans. This means that they can only take in oxygen from the air, but not from the water, like fish. That is why whales and dolphins come to the surface to breathe. The air supply is enough for more than a quarter of an hour!

2. While fish lay eggs, marine mammals give birth to their young alive and suckle them for the first few months of life. This is where the term "mammals" comes from.

3. Whales and dolphins have a constant body temperature. Fish, on the other hand, are "cold-blooded", which means that their body temperature depends on the temperature of the surrounding water.

These three characteristics make the differences between fish and mammals clear and show that whales and dolphins are mammals. Their fish-like appearance has developed over the course of millions of years. After all, they inhabit the same habitat as the fish and have therefore adapted to their environment in a similar way to this. Because the same environmental and living conditions often lead to similar solutions being developed for different animal species. Such an adaptation is also called evolution.

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