Why do cats have bellybuttons?

Cats actually do not have bellybuttons in the same sense that humans do. Humans have a belly button, also called the navel, the remnant of the umbilical cord through which nutrients from the mother's placenta reach the fetus during gestation. After the baby is born, the umbilical cord is cut, and the remaining stump eventually dries up and falls off, leaving a scar – the bellybutton.

In contrast, cats are born with abdominal walls completely closed. Cats have a different developmental process during gestation and do not have a placenta like humans. Instead, they have nutrient-rich tissue called the chorioallantoic membrane that lines the egg. Nutrients pass through this membrane directly to the developing cat without the need for an external umbilical cord.

Therefore, cats do not have a visible or distinct bellybutton like humans. Their abdominal walls are entirely sealed at birth, and there are no remnants or scars marking the site of nutrient exchange during fetal development.