Possums are marsupials, and their young develop uniquely among mammals. Unlike placental mammals, possums give birth to undeveloped offspring that continue their growth within the mother’s pouch. Their appearance transforms from birth until independence.
Physical Characteristics of Newborn Possums
At birth, a baby possum, or joey, is small and underdeveloped. A newborn joey measures about half an inch (12-13 mm), comparable to a jelly bean or a bumblebee. Their skin is pink, hairless, and translucent, allowing internal structures to be faintly visible.
These newborns possess rudimentary limbs, with forelimbs slightly more developed to facilitate their journey. Their eyes are fused shut, and their ears are barely formed, appearing as small folds of skin. Despite their undeveloped state, they are driven by instinct to crawl from the birth canal into the mother’s pouch, where they locate and firmly attach to one of her nipples. This early stage in the pouch is a vulnerable period for the joey.
Developmental Changes as They Grow
As a joey matures within the pouch, it undergoes physical transformations. After several weeks, a fine layer of fuzz begins to develop, gradually thickening into a soft coat of fur. This fur provides insulation and protection as the joey continues to grow.
Sensory organs also develop, with the joey’s eyes typically opening around 50 to 70 days after birth. At this time, their ears become more defined and functional, allowing them to perceive sounds. Their limbs strengthen, and the prehensile tail, initially short, lengthens and becomes capable of grasping and climbing.
The joey grows inside the pouch, eventually becoming too large to fit entirely. Around 70 to 100 days old, depending on the species, they begin to peek their heads out of the pouch. Soon after, they start to emerge completely, often riding on their mother’s back, a common behavior as they transition towards independence.
Distinguishing Baby Possums from Other Young Animals
Once baby possums are furred and visible outside the pouch, several distinct features help differentiate them from other young animals. A primary identifier is their unique tail, which is scaly, largely hairless or sparsely furred, and prehensile, meaning it can grasp objects. This contrasts with the bushy tails of squirrels or the uniformly thin tails of many rats.
Their facial features also offer clues, characterized by a pointed snout and relatively large, thin, leathery ears that stand upright. Possums also possess distinctive feet, particularly their hind feet, which feature an opposable “thumb” (hallux) that aids in gripping branches. This specialized digit is not found in most other common small mammals.
A baby possum’s overall body build tends to be stockier and more robust compared to the more slender bodies of young rodents like rats or mice. Observing their behavior, such as clinging to their mother’s back, can also provide an indication of their identity.