Do Opossums Eat Ticks? What the Research Really Says

Where did the “5,000 ticks” claim come from?

The idea traces back to a 2009 study by Felicia Keesing and colleagues, carried out with the Cary Institute of Ecosystem Studies in New York and published in the Proceedings of the Royal Society B. The researchers wanted to know how different wild hosts deal with blacklegged ticks, the species that spreads Lyme disease in eastern North America.

They captured several kinds of small mammals and birds, including the Virginia opossum, white-footed mice, squirrels and songbirds, and placed tick larvae on them in the laboratory. They then counted how many ticks fed successfully and dropped off. Opossums turned out to be excellent groomers: they removed and apparently killed most of the larvae, while white-footed mice let most ticks feed and survive.

From these numbers, rough estimates were made of how many ticks an opossum might kill in the wild, which reached thousands per week. Through press coverage, social media posts and memes, this became the catchy and much-repeated claim that an opossum eats around 5,000 ticks every season, or even that it eats 95 percent of the ticks it meets.

What did later research find?

The laboratory study measured grooming, not diet. It showed that ticks attached to an opossum often did not survive, but it did not show that opossums seek out and eat ticks in the wild, or that groomed-off ticks end up in the stomach.

In 2021, researchers Cecelia Hennessy and K. Hild tested the idea directly. They examined the stomach contents of wild Virginia opossums from Illinois and published the results in the journal Ticks and Tick-borne Diseases. They found no ticks in the opossums’ diet. Their paper’s title asked whether opossums are “really ecological traps for ticks”, and the answer from wild animals was that there is no sign of it.

Scientists have since pointed out that the 5,000-tick figure was never measured in wild animals and should not be repeated as fact. As of the mid-2020s, no published study has reported ticks as a meaningful part of the wild opossum diet.

So what do opossums actually eat?

Wild opossums are omnivores that eat whatever is easy to find. Stomach studies across the United States show a mix of small mammals and carrion, fruit, seeds and grain, grasses and leaves, insects, earthworms, snails, birds and their eggs, frogs and snakes. In towns, garbage and pet food left outdoors also appear.

Insects such as beetles, grasshoppers and crickets make up much of the animal food. In autumn, persimmons, berries and fallen apples become important. The full menu, including how opossums tolerate some snake venom, is covered in what do opossums eat?.

Do opossums help against Lyme disease?

Opossums may still play a small positive role in the Lyme disease story, but not by eating ticks. Lyme disease is caused by bacteria that ticks pick up when they feed on infected animals. White-footed mice are very efficient at passing the bacteria to young ticks, while many ticks that try to feed on opossums are groomed off and die before they can feed.

In theory, a forest with many opossums and fewer mice could produce fewer infected ticks. This idea, sometimes called the dilution effect, is still debated among ecologists, and it has not been shown that encouraging opossums lowers the risk of Lyme disease for people. Tick risk depends far more on deer numbers, mouse populations, weather and habitat. Adult blacklegged ticks feed mainly on white-tailed deer, so a few opossums in a neighborhood make little difference to how many ticks are waiting in the grass.

Why does the myth matter?

The tick myth has helped the opossum’s image, turning a creature many people found creepy into a backyard favorite. That goodwill is valuable, because opossums are harmless and genuinely useful: they eat insects, snails and slugs, clean up carrion and disperse the seeds of fruits such as persimmons and pawpaws.

The risk is that people rely on opossums instead of real tick protection. Health agencies advise people to take their own precautions against ticks, whatever animals live nearby.

Other opossum myths

Several other popular “possum facts” are only partly true. Opossums are not immune to rabies, though cases are rare. They are resistant, not fully immune, to the venom of North American pit vipers. They do not sleep hanging from their tails, and they do not mate through the nose. One famous claim is true, though: a frightened opossum really can collapse and play dead, as explained in why do opossums play dead?.