The question of whether manatees have belly buttons is an inquiry into the fundamental biology of these large, slow-moving aquatic creatures. Manatees, sometimes called sea cows, navigate warm coastal waters and rivers, growing up to 10 feet long and weighing over a thousand pounds. Examining this anatomical detail provides clear insight into the evolutionary history and reproductive strategy of these unique animals.
The Mammalian Marker
Manatees do possess a belly button, a feature that directly stems from their biological classification. The presence of this small scar is evidence that the manatee developed with a placenta inside its mother’s body. The placenta is an organ that forms during gestation to facilitate the exchange of nutrients, oxygen, and waste between the mother and the developing fetus. This exchange system requires an umbilical cord, which connects the fetus to the placenta. The cord contains blood vessels that act as the lifeline for the developing calf throughout the pregnancy. Once the calf is born, the connection is naturally severed, leaving behind a small patch of tissue on the abdomen. The remnant tissue dries and eventually falls off, leaving a permanent scar known as the umbilicus, or belly button. All three species of manatees—the West Indian, Amazonian, and West African—share this biological marker.
Appearance and Formation of the Umbilicus
The manatee’s belly button is not a prominent feature and looks quite different from the deep navel seen in humans. It appears as a small, subtle scar on the thick, wrinkled skin of the animal’s underside. Unlike a human’s navel, the manatee’s umbilicus is typically flat or recessed, making it difficult to spot on a living animal.
The location of this scar is consistently found near the middle of the body on the ventral, or belly, side. This placement is a useful anatomical landmark for biologists when examining the animals. For instance, the genital opening of a male manatee is located just behind its navel, while a female’s opening is situated farther back, closer to the anus.
The scar represents the point where the umbilical cord detached after birth, marking the transition from placental nourishment to independent feeding. The subtle nature of the scar is consistent with most non-human placental animals, where the remnant tissue heals into a discrete line or patch.
Marine Life Without Umbilici
The presence of a belly button in manatees highlights a sharp distinction between different groups of aquatic life. Most other animals inhabiting the ocean, such as fish, sharks, and sea turtles, do not have this scar. This absence is because their reproductive strategies do not involve a placenta and umbilical cord.
Fish and most marine reptiles reproduce by laying eggs, where the developing embryo receives all its required nutrition from the yolk sac. Since there is no physical connection to the mother’s body, there is no cord to detach and therefore no resulting scar. The young hatch directly from the egg, having completed their development nourished by the internal yolk. This biological rule reinforces that the belly button is an exclusive indicator of a live-birth, placental reproductive strategy. The manatee’s small, inconspicuous scar confirms its identity as a member of the placental lineage.