Neither label fits. American opossums and Australasian possums are both commonly called “possums,” but regardless of which animal you have in mind, slotting them neatly into “carnivore” or “herbivore” misses the mark. American opossums are classic omnivores whose digestive anatomy shows a mix of meat-eating and plant-eating features. Australasian possums lean heavily herbivorous, with some species surviving almost entirely on tough eucalyptus leaves, but even they bend the rules. The real answer depends on which “possum” you’re talking about, and the biology behind their diets is more interesting than either simple label suggests.
Two Very Different Animals Share the Name
The word “possum” gets applied to two groups of marsupials that split from each other tens of millions of years ago. In the Americas, the Virginia opossum (Didelphis virginiana) and its relatives belong to the order Didelphimorphia. In Australia, New Zealand, and nearby regions, brushtail possums, ringtail possums, sugar gliders, and their kin belong to the order Diprotodontia. They are about as closely related to each other as a kangaroo is to a wombat. Because their evolutionary histories diverged so long ago, their diets, digestive systems, and ecological roles differ substantially. When someone asks whether possums are carnivores or herbivores, the first useful question is: which possum?
American Opossums Are Textbook Omnivores
If you live in North or South America and find a possum in your garbage can, you’re dealing with a Didelphis species, and its gut tells the story of a generalist. A detailed anatomical study of the neotropical opossum (Didelphis marsupialis insularis) found that the lining of its esophagus and stomach lacked the thick keratinization you’d expect in a dedicated herbivore, while high concentrations of immune cells along the intestinal wall reflected a diet that regularly includes raw animal protein. At the same time, the animal had a well-developed caecum, a section of the large intestine used to ferment plant material. The researchers concluded that the overall structure of the digestive tract displayed both carnivorous and herbivorous features, confirming that the animal is genuinely omnivorous.1Acta Zoologica. Anatomy and histology of the gastrointestinal tract of the neo‐tropical opossum (Didelphis marsupialis insularis, Allen 1902)
In practice, what American opossums eat reads like a grab bag: fruit, insects, worms, small rodents, bird eggs, carrion, pet food left on porches, and whatever else is available. They are opportunistic in the truest sense. Their success across such a wide range of habitats, from tropical forests to suburban backyards, is partly explained by this dietary flexibility. They don’t need a specialized food source to survive, so they can show up almost anywhere there’s something edible.
Australian Possums Are Mostly Leaf Eaters
Australasian possums occupy a very different dietary niche. The common brushtail possum (Trichosurus vulpecula) and the common ringtail possum (Pseudocheirus peregrinus) are primarily folivores, meaning they eat leaves, and eucalyptus leaves in particular. This is a challenging diet. Eucalyptus foliage is low in nitrogen and calories, high in tough lignified fiber, and loaded with defensive chemicals like tannins and formylated phloroglucinol compounds (FPCs) that most animals can’t tolerate.
Research on brushtail possums fed eucalyptus foliage found that the high lignin content kept cell-wall digestibility low, at around 24%. Microscopic analysis showed that gut bacteria barely attached to the lignified plant tissues, making fermentation inefficient. The conversion of digested energy into usable energy was also poor compared to most herbivores, partly because the possums had to excrete metabolic byproducts of the leaf’s essential oils and phenolics in their urine. When researchers neutralized the tannins with a chemical binder, the possums ate more and digested more fiber, confirming that tannins were actively suppressing their food intake.2PubMed. Digestion and metabolism of high-tannin Eucalyptus foliage by the brushtail possum (Trichosurus vulpecula) (Marsupialia: Phalangeridae)
Ringtail possums handle the same problem differently. When tested with the same tannin-neutralizing treatment, ringtails showed no significant improvement in food intake or nitrogen digestion, suggesting they had already evolved ways to cope with tannins. The researchers proposed that dissociation of tannin-protein complexes takes place in the ringtail’s specialized caecum.3Journal of Zoology. Effects of tannins on digestion in the common ringtail possum (Pseudocheirus peregrinus), a specialized marsupial folivore But ringtails are more sensitive to FPCs, a different class of eucalyptus defense chemicals, while brushtails tolerate FPCs better but struggle more with tannins. This differential susceptibility helps explain why both species can coexist in the same forests: they effectively partition the eucalyptus menu by eating different trees or different parts of the canopy.4PubMed. Differential susceptibility to Eucalyptus secondary compounds explains feeding by the common ringtail (Pseudocheirus peregrinus) and common brushtail possum (Trichosurus vulpecula)
The Ringtail’s Secret Weapon
Getting enough nutrition from eucalyptus is so difficult that ringtail possums resort to a strategy most people would rather not hear about: they eat their own feces. Specifically, ringtails practice caecotrophy. During the day, while resting, they produce soft, nutrient-rich droppings from the caecum and eat them directly. These soft feces are high in water and nitrogen and low in fiber compared to the hard pellets the possums produce at night while foraging. This recycling loop is not trivial. In one study, caecotrophy contributed the equivalent of about 58% of the ringtail’s digestible energy intake and supplied twice the nitrogen needed for basic maintenance.5Australian Journal of Zoology. Coprophagy and Selective Retention of Fluid Digesta: Their Role in the Nutrition of the Common Ringtail Possum, Pseudocheirus Peregrinus
The digestive mechanics behind this are revealing. Ringtail possums selectively retain fluid and fine particles in the caecum for roughly twice as long as they retain large particles, giving bacteria more time to ferment the nutritious fraction while moving the indigestible bulk through quickly.6Comparative Biochemistry and Physiology Part A: Physiology. Digesta retention and fibre digestion in brushtail possums, ringtail possums and rabbits Brushtail possums, by contrast, do not show this selective retention pattern and do not practice caecotrophy. This helps explain why brushtails are more of a generalist feeder, supplementing their eucalyptus diet with fruit, flowers, and occasionally insects or bird eggs, while ringtails can get by almost entirely on leaves.
Sugar Gliders and Other Omnivorous Exceptions
Not all Australasian possums are strict leaf eaters. Sugar gliders (Petaurus breviceps) are a good example of the range within this group. A study of their diet in temperate Australia found that sugar gliders eat tree sap and gums from eucalyptus and acacia, blossoms, nectar, pollen, honeydew, and a wide variety of insects, arachnids, worms, larvae, eggs, and small vertebrates.7Journal of Animal Ecology. Diet and Feeding Strategies of the Marsupial Sugar Glider in Temperate Australia That diet covers just about every food category except large prey. Sugar gliders are firmly omnivorous, and their feeding strategy shifts seasonally depending on what’s available, leaning toward arthropods in summer and tree exudates in winter. Calling all Australian possums herbivores would leave out animals like these.
Opossums That Hunt Venomous Snakes
On the carnivorous end of the spectrum, large-bodied South American opossums in the clade Didelphini don’t just scavenge; they actively prey on venomous snakes. This sounds reckless, but these opossums carry biochemical armor. Research has identified at least two molecular defenses. First, their blood contains proteins related to human alpha-1B-glycoprotein that neutralize key components of snake venom, including metalloproteinases and phospholipase A2 myotoxins.8PubMed. Snake-venom resistance as a mammalian trophic adaptation: lessons from didelphid marsupials
Second, their von Willebrand factor, a protein involved in blood clotting, appears to have undergone rapid adaptive evolution. Snake venom C-type lectins normally bind to this protein and trigger dangerous clotting disruptions, but lab experiments found that opossum blood barely responds to these toxins. Platelet aggregation assays on two venom-resistant species (Didelphis virginiana and Didelphis aurita) showed nearly complete loss of the aggregation response to venom C-type lectins, and the resistance turned out to be intrinsic to the blood cells and clotting proteins themselves rather than something floating in the plasma that neutralizes the venom on contact.9PubMed Central. Resistance of South American opossums to vWF-binding venom C-type lectins
Even more unexpectedly, the short-tailed opossum (Monodelphis domestica), which is not closely related to the large Didelphis species and was expected to be venom-sensitive, also showed resistance to some venom-induced platelet disruption. Researchers additionally discovered that this opossum’s von Willebrand factor requires unusually high shear force to unfold, a previously unknown aspect of opossum blood physiology that may itself contribute to venom resistance.10PubMed Central. Comparative microfluidic and enzymatic analyses reveal multifaceted snake venom resistance and novel VWF behavior in the opossum Monodelphis domestica These adaptations are strong evidence that predation on venomous snakes has been a meaningful part of the opossum diet for long enough to drive molecular evolution.
The Tick-Eating Myth
One of the most widely repeated claims about Virginia opossums is that they devour thousands of ticks, making them valuable allies against Lyme disease. The origin of this idea traces to lab studies showing that captive opossums groomed off and appeared to eat large numbers of larval blacklegged ticks. An often-cited estimate was that a single opossum eats roughly 5,500 larval ticks per week. However, when researchers examined the stomach contents of 32 wild Virginia opossums from central Illinois, they found no ticks or tick parts whatsoever. A review of 23 additional published diet analyses of Virginia opossums, covering both stomach-content and scat-based studies, also turned up zero evidence of ticks as a diet item.11PubMed. Are Virginia opossums really ecological traps for ticks? Groundtruthing laboratory observations
That doesn’t mean opossums have no relationship with ticks. A separate study found that opossums and squirrels that are heavily parasitized by ticks in the wild kill 83 to 96% of the ticks that try to attach and feed, likely through grooming rather than deliberate consumption.12PubMed Central. Hosts as ecological traps for the vector of Lyme disease So opossums do reduce tick populations, but by dislodging and destroying ticks mechanically during grooming, not by eating them as a food source. The distinction matters: opossums are accidental tick killers, not tick predators, and the widely shared “5,500 ticks a week” figure almost certainly reflects unnatural lab behavior rather than what happens in the wild.
Opossums as Seed Dispersers
The plant-eating side of the American opossum diet has ecological consequences that are easy to overlook. In fragmented and disturbed tropical and subtropical habitats, opossums eat fruit and pass viable seeds through their digestive tracts. A study of white-eared opossums (Didelphis albiventris) in disturbed Brazilian forest found that these animals preferentially eat fruits with small seeds, swallow them intact, and an expressive proportion, up to 71% depending on the plant species, remain viable after defecation. Because opossums are highly mobile and tolerate urbanized landscapes well, researchers concluded that they participate meaningfully in natural reforestation, especially for early-succession plant species in degraded areas.13Biota Neotropica. Potential seed dispersal by Didelphis albiventris (Marsupialia, Didelphidae) in highly disturbed environment
Australasian possums also disperse seeds, though not always helpfully. In a New Zealand lowland forest, brushtail possums (an invasive species there) had an average of about 8 seeds per fecal sample, but they produced fewer droppings per day than birds and occurred at lower densities, so on a per-hectare basis they dispersed less than 3% of total seeds. Worse, possums destroyed about 15% of the seeds found in their feces and cut germination rates of some species to half of what bird-dispersed seeds achieved.14New Zealand Journal of Ecology. Quantifying seed dispersal by birds and possums in a lowland New Zealand forest In New Zealand’s context, possum seed dispersal provides little ecological benefit and may even favor the spread of weedy species over native ones.
When Herbivores Turn Predator in New Zealand
The brushtail possum in New Zealand deserves special mention because it shatters the assumption that “mostly herbivorous” means “harmless to other animals.” Introduced from Australia in the 1800s for the fur trade, brushtail possums are now one of New Zealand’s most damaging invasive mammals. While their primary diet in New Zealand is still foliage, flowers, and fruit, they also prey on the eggs and chicks of native birds, many of which evolved without mammalian predators and have no defense against them. Large-scale analyses of New Zealand forest bird populations found that possum predation on large bird species is a significant problem. When mammal control programs effectively reduced possum numbers but left rats and mustelids unchecked, the largest bird species still showed significant population increases, pointing to possums as a distinct source of predation pressure on those birds.15PubMed Central. Responses of New Zealand forest birds to management of introduced mammals
This is a useful reminder that dietary labels like “herbivore” describe a tendency, not an absolute rule. An animal that eats leaves 90% of the time can still cause serious damage to other species when it occasionally eats animal protein, especially if those other species never evolved to cope with that predation.
What Happens When Captive Possums Eat the Wrong Diet
The omnivorous nature of American opossums creates a practical problem for wildlife rehabilitators and anyone who keeps them in captivity. Opossums in the wild get calcium from bones, snail shells, and other hard animal parts, and they synthesize vitamin D through sun exposure. In captivity, where diets often consist of soft commercial foods and fruit, calcium deficiency is a real risk. A veterinary study documented rickets in captive white-eared opossums, attributing the metabolic bone disease to an imbalanced calcium-to-phosphorus ratio and insufficient vitamin D. The authors noted that there is no standard commercial diet formulated for opossums, so captive diets frequently fail to reproduce the nutritional balance these animals achieve in the wild.16Pesquisa Veterinária Brasileira. Rickets in white-eared opossums (Didelphis albiventris)
For Australian possums, the captive-diet challenge is different. Because their wild diet consists largely of toxic eucalyptus foliage that is impractical to supply in sufficient quantities, captive brushtail and ringtail possums are typically fed substitute vegetation and commercial feeds. Getting the balance of fiber, protein, and plant secondary compounds right matters, because these animals’ digestive systems evolved around specific chemical challenges that standard herbivore diets don’t replicate.
Urban Opossums and Human Food Waste
American opossums are increasingly common in cities, and their dietary flexibility is a big part of why. Virginia opossums are considered a textbook example of a species that thrives on human food waste, though research suggests the relationship is more nuanced than it first appears. A stable isotope study comparing the diets of Virginia opossums in urban areas and natural areas around Mexico City aimed to determine how much of the urban opossum’s diet actually consists of human-derived food versus natural forage.17Urban Ecosystems. Evaluation of the diet of Didelphis virginiana in an urban area using stable isotopes The premise that human garbage is “essential” for urban wildlife is widely accepted, but characterizing exactly how opossums use it, and whether urban individuals become nutritionally different from their wild counterparts, is still an active area of research. What is clear is that the same omnivorous flexibility that lets opossums eat fruit, insects, carrion, and the occasional snake also lets them eat pizza crusts and cat food, which is why they do so well in human-modified landscapes where specialist feeders struggle.