Strange lumps appearing on squirrels have alarmed US residents, but experts are urging caution — the bumps may not be harmless, and only trained professionals should intervene.

An animal rescue center in the US has cautioned anyone who might be tempted to try and help squirrels with ‘unusual looking skin lumps’, warning it’s likely the result of a parasite.

Just days after rabbits with so-called ‘tentacles’ growing out of their heads were spotted in the US, Americans are now being warned about another unsettling sight: squirrels covered in swollen growths.

These are not the result of overeating nuts or seeds, but visible lumps and bumps pushing through their fur.

For several years, Evelyn’s Wildlife Refuge in Virginia has issued seasonal warnings via Facebook, explaining that the lumps often appear in autumn when squirrels are carrying a parasite that “tunnels through the flesh, causing swollen protrusions.”

Botflies cause obvious protrusions on the squirrel’s body (Getty Stock Photo)

The parasite is identified as a botfly, part of the Oestridae family.

Squirrels are among the most common hosts, but other animals such as dogs, cats, rabbits, raccoons, and chipmunks can also be affected. Infection occurs when an animal comes into contact with botfly eggs. The eggs hatch into larvae, which burrow under the skin — sometimes even entering through the nose or mouth.

Once inside, the larvae grow, creating the swollen lumps visible on the surface. When fully developed, they emerge from the host, drop to the ground, and bury themselves before becoming adult flies.

Though distressing, experts emphasize that botflies usually do not kill their hosts. However, Evelyn’s Wildlife Refuge strongly warns that removal attempts should only be made by trained professionals.

Evelyn’s Wildlife Rescue urged people not to help infected squirrels (Facebook/Evelyn’s Wildlife Rescue)

In its latest post, the center stressed: “Only skilled rehabbers or vets should attempt to extract bots. If the larvae’s body is compromised inside the host, anaphylactic shock and possible death is possible. These guys have something like legs that will ‘dig in’ the host in an effort to prevent removal. Caution should still be exercised during removal even if the bot is dead.”

To help the public distinguish between conditions, Evelyn’s also shared an image of a squirrel suffering from squirrel pox, which causes smaller bumps often spread at feeders. Unlike botfly infestations, squirrel pox generally clears on its own over time.