Do any animals stay the same size as when they are born?

No, all animals grow after birth.

While some animals grow very little after birth compared to others, they still increase in size. Here are a few examples:

* Insects: Many insects, like grasshoppers or beetles, have a fixed size after they molt into their adult form. However, they still grow significantly from their larval stage.

* Fish: Some fish species, like sharks, continue to grow throughout their lives, but at a much slower rate than during their early stages.

* Reptiles: Reptiles like turtles and crocodiles grow for many years, but their growth slows down as they age.

Even though some animals reach a size close to their adult size quickly, they all experience some growth after birth.