Here's why it's tricky:
* There's no single trait that only 5% of animals have. The animal kingdom is incredibly diverse, and traits are distributed in many different ways.
* Percentages are relative to the group you're looking at. For example, 5% of all animals might be a certain type of insect, but that doesn't mean only 5% of insects have that trait.
Let's look at some examples:
* Backbones: Only about 5% of all animals have backbones (vertebrates). However, this includes a vast number of creatures – mammals, birds, reptiles, amphibians, and fish!
* Wings: A very small percentage of animals have wings. This includes birds, bats, and some insects.
* Warm blood: Only a small percentage of animals are warm-blooded, mostly mammals and birds.
So, the answer is: There's no single thing that only 5% of animals have.
It's more helpful to think about the wide variety of traits found in the animal kingdom and how they are distributed.