Regardless of the size or age of a leopard seal, a clear view (or photograph) of the ventral surface allows the sexes to be differentiated. Both sexes have a scar from the umbilical attachment (belly-button). The males (♂) have a penile opening approximately half way between the umbilcal scar and the hind flippers, whilst the females (♀) have two small mammary glands which are often visible.