Look closely at an opossum track in soft mud and one hind print will look wrong compared to everything around it — lopsided, with one digit splayed far out to the side rather than lined up with the rest. That is not a deformity or an injury. It is the opossum's hallux, a fully opposable, clawless big toe that functions more like a thumb than a toe, and it is the single feature that most clearly separates the opossum's foot from every other mammal sharing its habitat.
Five Toes, Two Very Different Front and Back Designs
Opossums have five digits on both front and hind feet, but the two pairs of feet do very different jobs. The front feet are built for general-purpose use: all five toes carry claws, spread widely for stability on uneven ground, and are dexterous enough to manipulate food, grip nesting material, and probe into leaf litter or shallow water while foraging. There is nothing especially unusual about the front foot compared to a raccoon's or squirrel's — it is a capable, clawed, five-fingered paw.
The hind foot is where the opossum diverges from nearly every other mammal in North America. Four of the five hind toes are clawed and arranged in a fairly ordinary fan, but the innermost digit — the hallux — has no claw at all and sits at almost a right angle to the others, able to swing inward and grip against the remaining toes the way a human thumb opposes the fingers.
A true opposable digit that can grip against the rest of the foot is rare among mammals generally and essentially unique among North American land mammals. It is more commonly associated with primates and some other marsupials, which is a reminder that opossums are not rodents — they are marsupials, more closely related to kangaroos than to rats.
What the Hallux Is Actually For
The clawless, opposable hind toe gives the opossum a genuine grasping foot, which pairs with its prehensile tail — covered in detail in our piece on the Virginia opossum's prehensile tail — to make it a far more capable climber than its slow, waddling gait on the ground would suggest. On a branch, the hind foot can wrap around and grip in a way a raccoon's or squirrel's clawed foot cannot quite replicate, since those species rely on claws digging into bark rather than a true grip. The tradeoff is that the hallux, lacking a claw, provides no traction on hard, smooth, or vertical surfaces the way a claw would, which is part of why opossums are competent but unspectacular climbers compared to squirrels.
A Track That Identifies Itself
For anyone trying to identify wildlife by footprints alone, the opossum's hind track is close to unmistakable once you know what to look for: a star-shaped or asymmetric print with one digit angled sharply away from the rest. No other common backyard mammal — not raccoons, not squirrels, not rabbits — produces anything similar, which makes hind tracks the single most reliable sign for confirming an opossum has been through an area, even when no other evidence is present. Our guide to reading opossum tracks and signs covers this and other markers in more detail.
Front Feet and Fine Manipulation
While the hind foot gets the attention for its unusual hallux, the front feet do most of the fine manipulation work involved in foraging. Opossums are opportunistic omnivores that handle a wide range of food items — insects, fruit, carrion, eggs — and the dexterity of the clawed front paws allows them to pin, turn, and tear food in ways that a strictly grasping hind foot could not manage on its own. The front feet also bear more of the animal's weight during its characteristic low, flat-footed gait, since opossums are plantigrade walkers, placing the entire sole of the foot on the ground with each step rather than walking on their toes the way a dog or cat does.
An Ancient Design
This grasping-hind-foot, plantigrade-gait body plan is considered a relatively conservative one among mammals — it has changed comparatively little over a very long evolutionary history, which is part of why opossums are sometimes described as living close to an ancestral mammalian body form. Academic species accounts, including the University of Michigan's Animal Diversity Web, describe this generalized limb and foot structure as one reason opossums have been able to persist across such a wide range of habitats with relatively little specialization required. It is not a flashy adaptation compared to a bat's wing or a mole's digging claw, but it is versatile, and versatility has clearly worked out well for the species.