The answer to whether opossums lay eggs is a clear and definitive no. These creatures are mammals, and the Virginia opossum is North America’s only native species of its kind. Their distinct reproductive process involves a very short internal development followed by an extended period of growth within a specialized external structure.
Mammals, Not Monotremes
Opossums belong to the class Mammalia, characterized by having hair and feeding their young with milk. Mammals are divided into three groups based on reproductive strategy: placental mammals, marsupials, and monotremes. Placental mammals, like humans and dogs, develop the embryo internally for a long period within a uterus. The monotremes, which include only the platypus and the echidna, are the only mammals that reproduce by laying eggs. Opossums are marsupials, meaning they follow a reproductive path that is neither egg-laying nor fully placental. Marsupial reproduction involves giving birth to extremely undeveloped young after a brief internal gestation.
The Opossum Reproductive Process
The female opossum’s anatomy is specialized for reproduction, featuring a divided reproductive tract with two vaginal canals and two uterine horns. Fertilization occurs internally, leading to a short gestation period lasting only 11 to 13 days. Following this brief development, the female gives birth to a large litter that can number up to twenty or more. At birth, the young are in a nearly embryonic state, blind, hairless, and incredibly tiny. The newborns must immediately begin an unaided journey, using their developed forelimbs to crawl across the mother’s fur toward the external abdominal pouch.
Life Inside the Pouch
Young that successfully complete the crawl enter the pouch, known as the marsupium. Inside this protective environment, each newborn must find and firmly attach itself to one of the mother’s specialized teats. The mother typically has 13 teats, so any young that fail to secure a spot will not survive. Once latched, the teat swells slightly inside the infant’s mouth, locking the young in place for continuous nursing and rapid growth. During this time, they develop sight, grow fur, and transition from their embryonic state into recognizable young, often referred to as joeys.
The young typically remain within the pouch for about 70 days. As they grow too large to fit comfortably, they begin to emerge and cling to the mother’s back. They ride with her as she forages, learning survival skills before they are weaned around three months of age. The young opossums become independent at about four to five months old.