Opossums, North America’s only marsupials, often spark curiosity. Distinguishing the sex of a baby opossum can be challenging, but understanding their unique biology and developmental stages provides insight into their identification. This guide explores visual cues and developmental timelines.
Visual Indicators for Sexing
Identifying the sex of a baby opossum involves examining the ventral region, between the hind legs and near the tail. In male baby opossums, testicles appear as a small, sometimes furless, bulge just in front of the anus, growing larger and furrier over time. Male opossums also possess a bifurcated, or fork-shaped, penis, and two distinct scrotal sacs.
Conversely, female baby opossums lack the prominent scrotal sac seen in males. Instead, they exhibit a smoother area above the tail leading to the cloaca, a single opening for reproductive, urinary, and digestive functions. Females also have a fur-lined pouch, or marsupium, near the lower abdomen. In very young “pinkies” (hairless neonates), this pouch might appear as a subtle fold of skin or a small circular area with visible nipple dots.
Age and Development
The age and developmental stage of a baby opossum significantly influence sex identification. Opossums are born in an extremely underdeveloped, embryonic state. At this very early “pinky” stage, when they are hairless, their external sex characteristics are not yet fully formed, making visual sexing very difficult.
As joeys grow and remain in the pouch for about two to three months, their features become more defined. Male testicles typically become noticeable around 7 days after birth, and by approximately 24 to 28 days old, the testes have descended into the scrotal sac, making them more apparent. Visual identification becomes much more feasible once young opossums are out of the pouch and have grown to at least four inches, excluding their tail.
Important Considerations for Handling
When encountering a baby opossum, prioritize its well-being and safety. Minimize direct handling of any wild animal to reduce stress and prevent potential harm to both the animal and yourself. If a baby opossum appears orphaned, injured, or in distress, contact a licensed wildlife rehabilitator immediately.
Attempting to care for a wild animal yourself without proper licensing or experience can inadvertently cause more harm, potentially leading to illness or death. If a baby opossum is less than seven inches long, excluding its tail, or if its eyes are not yet open, it is likely too young to survive independently and requires professional intervention. If any brief contact is unavoidable, wearing gloves and washing hands afterward is a basic hygiene precaution.