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That Drooling, Hissing Daytime Opossum You Thought Had Rabies, Probably Didn’t

By Dawn Papple
Published on: 10:11 PST, May 29, 2016

When people see an opossum out during the day, they commonly begin to suspect that the opossum is sick and maybe even carrying rabies. Rabies concerns are substantiated in their minds when they go in for a closer look and the marsupial hisses with a mouth full of drool and an aggressive, erratic gait. Many an opossum has met their doom from a nature lover with a gun, trying to put the animal they believe is rabid, out of their misery. The only problem is that the animal almost certainly did not have rabies. In fact, it’s possible that it wasn’t even sick.

See, opossums have a very low body temperature compared to other mammals. This is probably why, according to the Opossum Society of the United States, the rabies virus has such a difficult time surviving in an opossum’s body.

That aggressive-looking hissing of the opossum’s drooling, open mouth is actually typical of the bluffing nature of this normally passive animal. They aren’t natural fighters, so the vicious front they put forth is merely a nervous defense. If you were to scare them even a little more, they’d likely fall over and play dead. The Humane Society explains this on their website.

“People often mistake the open-mouth hissing and drooling behavior of opossums as a sign of rabies. However, this is just a bluffing behavior that opossums use as a defense mechanism and does not indicate a sick animal.”

Rabies is extremely rare in opossums and some opossum experts even question whether it’s even possible for the virus to establish itself in the body of this mammal enough to transmit rabies at all, according to the Bi-State Wildlife Hotline, which explained candidly the defensive nature of this marsupial.

“When a ‘possum is approached, it will open its mouth widely, show you all of their teeth, and begin to drool excessively. Usually this pose is enough to intimidate anyone, and you will leave it alone. Even in baby opossums we see this defense mechanism, although we’re so used to it that it is less than intimidating to us anymore. If pushed, cornered, poked, prodded, the opossum WILL bite, but it will never run after you, chase you, come towards you in an attacking way. No matter what you hear, opossums are not out there killing people’s dogs, or attacking children. They do not care about your dog, and they don’t want anything to do with your children. Opossums hope that they can bluff their way out of any human encounter, but it doesn’t always work.”

Rabies (Lyssavirus) is transmitted through the saliva a few days before the death of an infected animal. It isn’t transmitted through blood, urine, or feces. It is not an airborne virus. In the furious form of rabies, wild animals seem agitated, aggressive and drool in excess. Rabies can be transmitted to others during the final stage of the disease when it has traveled from the brain to the salivary glands. When a nocturnal animal is out during the day, it is sometimes because it is confused, and confusion is a side effect of rabies.

If an opossum is out during the day, though, it’s usually for a different reason. These non-aggressive animals will do whatever they can to avoid trouble. They regularly will seek refuge from something that scares them up in a tree. They will stay in the tree all night in order to avoid a fox or coyote in the area. After morning comes and the predator has gone home to sleep, the opossum still has foraging to do or is still too unsettled to return home.

“Opossums are occasionally found on fences or in trees after they have been chased by dogs,” Wildlife Hotline explained. “Usually, opossums are still too frightened by morning to come down from their safe spot, and often will wait until the following night to return to their den.”

According to the Bi-State Wildlife Hotline, many Americans fear rabies far more than they should at this point anyway. Though it was once much more prevalent in the U.S., thanks to rabies eradication efforts and post-exposure treatment, rabies only kills about three people in the United States each year. When people have contracted rabies, it’s almost always from an infected bat. Raccoons get rabies more than any other mammal in the United States, but the raccoon strain of rabies is responsible for only one death recorded in the U.S. in total recorded history.

Opossums are often completely misunderstood, according to the Humane Society. Opossums are the unsung heroes in a fight against Lyme disease thanks to their knack for eating vast amounts of ticks and tick larvae. They also can clear a garden of pests like snails, slugs, and small rodents. For people who live in areas with poisonous snakes, an opossum you spot could just be a dark knight that prevented a venomous bite on a child. Indeed, opossums even eat venomous snakes, because they are highly resistant to the venom of snakes like copperheads or rattlesnakes.

They are nomads, wandering around eating fallen, spoiled fruits (which is a favorite of mosquitoes), cleaning up garbage and scavenging dead things.

While there is evidence that opossums can carry Equine Protozoal Myeloencephalitis (EPM), which is dangerous to horses, according to the Washington Department of Fish and Wildlife, EPM causes actual disease in only one percent of exposed horses. In order to be susceptible to EMP, horses must usually be exposed to enduring stress. It is estimated that EMP affects only 14 out of every 10,000 horses. EMP also requires two hosts in order for transmission: a definitive and intermediate host.

“Opossums are infected by eating sarcocyst-containing muscle tissue from an infected intermediate (prey) host and, after a brief prepatent period (probably 2–4 wk), infectious sporocysts are passed in the feces. Nine-banded armadillos, striped skunks, raccoon, sea otters, Pacific harbor seals, and domestic cats have all been implicated as intermediate hosts,” according to the Merck Veterinary Manual. Up to 65 percent of horses in the United States can show antibodies for EMP, but most never exhibit any symptoms of the disease.

Other concerns about opossums include dangers to chickens and other fowl. Farmers find that securing their pens is usually enough to protect their livestock from an opossum, something that should be done anyway to protect chickens from other predators that are far more persistent than a foraging opossum. Still, if another predator kills a chicken, a lazy opossum is delighted to clean up any leftovers that might be easily accessible.

They are often accused of killing pet cats, but it is generally believed that when someone sees an opossum eating a cat, it’s likely that the cat had been killed by the time the opossum found it. Opossums like dead animals because they are also scavengers.

They naturally protect humans and their pets and livestock from things exceedingly more dangerous and pesky than they are.

“A lot of people who call the hotline have the wrong idea about opossums,” a writer for the Bi-State Wildlife Hotline reported. “No, they do not have rabies. In fact it is EXTREMELY rare if even POSSIBLE for opossums to get rabies because their body temperature is too low for rabies to survive and replicate well. The usual reason people think they have rabies is the drooling that opossums do when approached and scared.”

[image via Pixabay]

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