Baby possums are born in an almost embryonic state, looking nothing like the pointy-nosed, furry animals they will become. A newborn Virginia opossum weighs roughly a tenth of a gram and is about the size of a honeybee, with translucent skin, sealed eyes, and hindlimbs that are little more than tiny buds. Over the next several months, these remarkably undeveloped creatures undergo a transformation that is dramatic even by marsupial standards, passing through stages where they look like pink jellybeans, then miniature mice, then fuzzy hitchhikers clinging to their mother’s back, and finally independent juveniles that are recognizably opossums.
At Birth, They Barely Look Like Animals
The Virginia opossum has one of the shortest gestation periods of any North American mammal, roughly twelve to thirteen days. The result is a newborn that looks far more like a larval insect than a mammal. At birth, a baby opossum (sometimes called a joey, borrowing the term from other marsupials) is hairless, pink, and so small that an entire litter can fit in a tablespoon. The skin is thin enough that internal organs are faintly visible beneath it. The eyes are completely sealed under a layer of fused skin, and the ears are flat, undeveloped flaps pressed against the head.
What is striking about a newborn opossum is the contrast between its forelimbs and the rest of its body. The front legs are disproportionately developed, equipped with tiny claws that allow the newborn to crawl, unaided, from the birth canal into the mother’s pouch. The hindlimbs, by contrast, are essentially stumps with no functional toes. The tail is a thin, nearly featureless thread. There is no visible fur, no whiskers, and no discernible snout shape. If you placed a newborn opossum next to a newborn rat or even a large insect, most people would not guess it was a mammal at all.
The First Weeks Inside the Pouch
Once inside the pouch, each baby latches onto one of the mother’s nipples, which swells inside the joey’s mouth to create a semi-permanent attachment. For the first several weeks, the babies remain firmly attached and do essentially nothing except nurse and grow. During this period, they still look like tiny pink grubs. Their bodies are smooth and translucent-pink, and their limbs remain stubby. Growth during this early pouch phase is steady and predictable. Research tracking young pouch opossums found a uniform increase in body length during the first ten weeks of life, with growth following a linear pattern regardless of the joey’s sex or litter size.1PubMed Central. General observations on the growth and development of the young pouch opossum, Didelphis virginiana
During weeks two through four, the changes are subtle but real. The hindlimbs begin to lengthen and develop distinct toes, though they are still not functional for gripping. The tail grows longer and thinner. The head, which was disproportionately large at birth relative to the body, begins to take on a slightly more elongated shape. The skin remains hairless and pink throughout this stage. To the casual observer, a two-week-old opossum in the pouch looks almost identical to a newborn, just slightly bigger.
When Fur Appears and Features Take Shape
Somewhere around weeks five through seven, baby opossums start to undergo their most visually dramatic transformation. Fine, velvety fur begins to appear, usually showing up first along the back and gradually spreading to cover the rest of the body. The fur is initially very short and may look like a faint gray fuzz, giving the previously pink animal a slightly dusty appearance. Over the following weeks, the characteristic coloring of the Virginia opossum starts to emerge: a grayish-white body coat with darker fur on the legs and around the face.
During this same window, the ears begin to unfurl and stand away from the head. In very young joeys, the ears are thin, crinkled, and sometimes partially transparent. They darken and stiffen over time. The snout elongates noticeably, beginning to show the long, pointed shape that adult opossums are known for. Whiskers start to sprout. By the time a baby opossum is around seven to eight weeks old, it is starting to look like a recognizable opossum in miniature, though its proportions are still off. The head and ears appear oversized for the body, and the legs are short relative to the torso.
The eyes are one of the last major features to become functional. The eyelids remain sealed for roughly the first two months. When they finally open, the eyes are dark, round, and prominent. Eye opening is a major developmental milestone because it coincides roughly with the period when joeys begin to detach from the nipple voluntarily and start moving around inside the pouch on their own.
Leaving the Pouch and Riding on Mom’s Back
By around 70 to 80 days of age, baby opossums begin venturing out of the pouch. They do not leave permanently all at once. Instead, there is a transitional period where they climb in and out, spending increasing amounts of time outside. At this stage, they are roughly the size of a small mouse, fully furred, with open eyes and functional ears. Their tails have developed enough prehensile ability to wrap loosely around objects, though they are not yet strong enough to support the animal’s full weight.
The classic image of baby opossums riding on their mother’s back corresponds to this stage. A mother opossum walking through a yard or along a fence with half a dozen miniature opossums clinging to her fur is one of the more distinctive sights in North American wildlife. The babies grip the mother’s back fur with their claws and sometimes wrap their tails around hers for extra stability. They are alert, bright-eyed, and look like shrunken adult opossums, though their fur is often softer and slightly lighter in color than the mother’s coarser coat. Their faces may appear rounder and less angular than an adult’s.
Weight gain accelerates during this period. Research on captive Virginia opossums recorded a mean body weight of about 14 grams at 50 days of age, which then increased rapidly over the following months, reaching roughly 2,560 grams by 233 days.2Karger (Biol Neonate / PubMed Central). Development of the neonate opossum (Didelphis virginiana) That is a jump from about half an ounce to over five pounds in less than seven months, reflecting just how compressed and intense marsupial postnatal development is compared to placental mammals.
The Juvenile Stage
By roughly three to four months of age, young opossums are weaned and beginning to forage independently. At this point they look like smaller, slightly scruffier versions of adults. Their fur is fully grown in but may lack the coarser guard hairs that give adult opossums their somewhat grizzled appearance. The body proportions have mostly normalized: the head no longer appears oversized, and the limbs are long enough for efficient climbing and walking. The tail is long, mostly hairless, and capable of gripping branches, though juveniles tend to be clumsier climbers than adults.
Juvenile opossums are sometimes mistaken for rats by people who are not familiar with the species, especially when seen at a distance or in dim light. The key visual differences are the opossum’s pointed white face, prominent rounded ears (which are often black-tipped or entirely dark), and a thicker, more muscular-looking tail compared to a rat’s thinner, scaly one. Juveniles also tend to move with a distinctive slow, waddling gait rather than the quick darting movements typical of rodents.
By five to six months old, a young Virginia opossum is close to adult size and essentially indistinguishable from a mature animal unless examined closely. Adults typically weigh somewhere between four and fourteen pounds depending on sex, season, and available food, with males tending to be larger. The entire journey from a translucent, honeybee-sized newborn to a fully grown animal takes less than a year, which is fast by mammalian standards but makes sense for a species whose total lifespan in the wild averages only about two years.
How Litter Size Affects What You See
Virginia opossums can give birth to large litters, sometimes more than a dozen at once. However, the mother typically has only thirteen nipples (the exact number varies slightly), and any newborn that does not find and attach to a nipple will not survive. This means that the number of babies you see in the pouch or riding on the mother’s back is constrained by nipple availability, not birth count. Litters of six to nine surviving joeys are common.
Despite concerns people sometimes have that larger litters might produce smaller or less developed babies, research has found that growth patterns remain consistent regardless of litter size.1PubMed Central. General observations on the growth and development of the young pouch opossum, Didelphis virginiana A joey from a litter of five and a joey from a litter of ten follow essentially the same growth curve. This consistency means that if you find baby opossums and want to estimate their age based on size or developmental features, the number of siblings does not change your assessment.
Telling the Difference Between Opossums and Other Baby Marsupials
If you live in North America, the Virginia opossum is the only marsupial you will encounter. But the word “possum” is also widely used in Australia and neighboring regions to refer to entirely different animals, most commonly the brushtail possum (Trichosurus vulpecula). The developmental stages are broadly similar because both are marsupials with comparable reproductive strategies, but the details differ.
Brushtail possum mothers typically carry just one joey at a time, occasionally two. The baby brushtail possum follows a similar general trajectory: born tiny and undeveloped, it spends months in the pouch growing and developing fur before emerging. One studied difference involves thermoregulation. Young brushtail possums cannot maintain a steady body temperature on their own until roughly 140 to 167 days after birth, meaning they depend on the pouch’s warmth for far longer than their appearance might suggest.3PubMed. The development of thermoregulation in the marsupial brushtail possum Trichosurus vulpecula A baby brushtail possum that looks fully furred and capable may still be physiologically dependent on its mother’s body heat.
Visually, juvenile brushtail possums look quite different from juvenile Virginia opossums. Brushtail possums have large, rounded ears, a bushier tail (hence the name), and a rounder face with bigger eyes. Their fur tends to be thicker and more uniformly colored, usually a warm brown or gray. The Virginia opossum, by contrast, has a more rat-like appearance with its pointed snout, thinner tail, and coarser, patchier-looking fur. If you see a photo of a baby “possum” online and it looks adorable, round-faced, and fluffy, it is almost certainly an Australian species. Virginia opossum babies are many things, but conventionally cute is not one of them until they reach the back-riding stage.
What to Do If You Find Baby Opossums
Knowing what baby opossums look like at different stages has practical value if you encounter them. The most common scenario is finding orphaned babies, either still attached to the body of a mother killed by a car or scattered near a deceased or injured adult. How you respond depends on the developmental stage.
If the babies are still pink, hairless, and smaller than your thumb, they are very young and completely dependent on constant warmth and specialized care. They cannot eat solid food, regulate their own body temperature, or survive any period of exposure. These animals need a licensed wildlife rehabilitator immediately. Do not attempt to feed them cow’s milk, infant formula, or any household liquid, as their digestive systems are not equipped to handle anything except opossum milk at this stage.
If the babies are furred, have open eyes, and are roughly the size of a large mouse or small rat (typically seven inches or longer from nose to rump, not counting the tail), they may be old enough to survive on their own. A good rule of thumb used by many wildlife rehabilitators is that if the baby opossum is at least seven to eight inches long, it has likely already been weaning and can forage independently. These juveniles may look small and vulnerable, but opossums mature fast and are surprisingly self-sufficient at a young age.
Baby opossums found riding on a live mother’s back should generally be left alone. The mother is caring for them normally. If you see a mother opossum moving through your yard with babies clinging to her, she is not in distress; she is doing exactly what opossums do during the back-riding stage. Interfering by trying to remove the babies or relocating the mother can separate the family and reduce the babies’ chances of survival.
Why Opossums Develop So Differently from Other North American Mammals
The reason baby opossums look so strikingly undeveloped at birth compared to, say, a newborn rabbit or squirrel has to do with the marsupial reproductive strategy. Marsupials invest less in gestation and more in postnatal development. The trade-off is a very short pregnancy followed by a long period of pouch-based growth. A newborn rabbit is blind and hairless but still weighs several grams and has four functional limbs. A newborn opossum weighs a fraction of a gram and has functional forelimbs only because it needs them to crawl to the pouch; everything else develops after arrival.
This strategy has advantages. A short gestation means the mother invests relatively little energy before birth, so if conditions turn bad, she has not lost months of pregnancy. She can also potentially produce multiple litters in a single year. Virginia opossums in warmer climates sometimes raise two or even three litters annually. The cost is that the babies are extraordinarily vulnerable during their pouch phase and require an extended period of maternal care that, while different in form from placental mammal pregnancy, is comparable in total duration and energy investment.
The developmental measurements tracked in research on Virginia opossums show just how much of the body plan assembles after birth. Between 50 and 189 days, researchers recorded weekly changes in total body length, ear length, tail length, and limb dimensions, all of which were still actively growing and changing proportions throughout that window.2Karger (Biol Neonate / PubMed Central). Development of the neonate opossum (Didelphis virginiana) Features that would be fully formed at birth in a placental mammal, like ear shape and limb proportions, are still under active construction months after an opossum is born. This is why baby opossums at different stages can look so drastically different from one another, and why a two-week-old and a ten-week-old opossum might not be recognizable as the same species to someone unfamiliar with their development.