Most animals do actually have belly buttons although it appears the animal has no belly button.
Only placental mammals will have belly buttons.
Marsupials, such as kangaroos, koalas and opossums, give birth to relatively underdeveloped young.
Before they are born, they get their nutrients from a yolk sac in their mother's womb.
The reason animals don't appear to have belly buttons is because usually with an animal the mother chews off the babies umbilical cord and it's not cut off and tied off like a human babies umbilical cord.
The belly button of an animal can be harder to find and will look slightly different than a humans belly button.
If you look close enough at an animals body you can see the belly button but it's usually small and hard to see.
All mammals that have live birth have a belly button - they're just not always easy to find.
Belly buttons are the scar left behind where the umbilical cord - which delivers nutrition and oxygen from mom to baby while in utero - was severed off just after birth.
You will not find belly buttons on animals like birds and reptiles, but you will find them on most, but not all, mammals.
However, the belly buttons on squirrels, tigers, and even whales aren't as noticeable as the belly buttons you would find on people.
To know why, you have to first understand a few basics.