The North American Opossum, Didelphis virginiana, is often misunderstood but poses a minimal threat to humans and domestic pets. The opossum is a naturally non-aggressive creature, and its presence often indicates a balanced local ecosystem. While any wild animal presents some risk, the dangers associated with the opossum are generally low and often exaggerated. Understanding their natural behavior and limited health risks can help people coexist safely with this unique animal.
Understanding Opossum Behavior and Aggression
Opossums are solitary and primarily nocturnal, which limits their interaction with humans and daytime pets. When threatened, their first response is not to attack but to display a dramatic fear response. This may involve hissing, screeching, and drooling, intended to deter a predator by making the opossum appear sick or formidable.
Their most famous defensive act, “playing possum,” is an involuntary physiological reaction to extreme fear. The opossum enters a catatonic state, falling on its side with its mouth slack and eyes open. It simultaneously emits a foul odor from its anal glands to mimic the smell of decay. This state, known as thanatosis, can last for minutes to hours and is highly effective at causing a predator to lose interest.
A bite from an opossum is extremely rare and nearly always occurs only if the animal is cornered, trapped, or actively handled. These animals prefer to retreat or feign death rather than engage in a physical fight. They are not predatory toward humans or pets, and their aggression is purely a defense mechanism driven by fear.
Assessing the Risk of Disease Transmission
A common concern about opossums centers on rabies transmission, but the risk is exceptionally low compared to other wild mammals. The opossum’s naturally low internal body temperature, ranging from about 94 to 97 degrees Fahrenheit, makes it difficult for the rabies virus to survive and replicate. This biological trait means that clinical cases of rabies in opossums are uncommon.
While rabies is rare, opossums can transmit other pathogens indirectly through their waste or parasites. They may carry the bacteria responsible for leptospirosis and salmonellosis, transmitted through contact with their urine or feces. Opossums also host external parasites like fleas and ticks, which can act as vectors for diseases such as tularemia and murine typhus.
A specific health concern related to opossum feces is Equine Protozoal Myeloencephalitis (EPM), a neurological disease affecting horses. Opossums can pass the protozoan Sarcocystis neurona in their droppings. This can infect horses if they ingest contaminated feed or water, emphasizing the importance of managing opossums near livestock areas.
Practical Steps for Safe Coexistence
The most effective way to coexist safely with opossums is to remove or secure common attractants from your property. Since they are scavengers, securing garbage cans with tight-fitting lids will eliminate a primary food source. Pet food and water dishes should never be left outside, especially overnight, as they draw in opossums and other wildlife.
Preventing them from seeking shelter in or under structures is also important for reducing encounters. Homeowners can seal off access points to crawl spaces, sheds, and decks to discourage denning. If an opossum is found in an undesirable location, non-lethal deterrents such as bright lights or loud noise can encourage the nocturnal animal to move on.
If a pet encounters an opossum, manage the situation calmly and prevent direct contact. Opossums will likely use defensive behaviors, such as hissing or playing dead, rather than attacking. Keeping pets up-to-date on vaccinations for diseases like leptospirosis provides an extra layer of protection against potential indirect transmission.