GRAY SQUIRRELS AREN’T GOING NUTS

August 30, 2006
CONTACT: Paige Martin (850) 265-3676

Every year about this time people call the Florida Fish and Wildlife Conservation Commission (FWC), alarmed about squirrels that seem to be going crazy. They report that they’ve seen squirrels rolling on the ground, jumping in the air and generally acting as if something was disturbing them.

But don’t worry, they’re not crazy. They’re likely hosting a parasite that causes them some temporary discomfort, but generally is not fatal.

When the people call, they describe the squirrels’ unusual antics, as well as large lumps that appear to be cancerous tumors on the squirrels’ bodies, according to FWC wildlife biologist Paige Martin.  In fact, the lumps are “subcutaneous warbles” caused by the larvae of insects commonly known as bot flies.

In the southeastern United States, gray squirrels, other rodents and rabbits are common hosts to these larvae. Adult female flies deposit eggs in the immediate vicinity of the hosts’ nests or dens where the host comes into contact with the eggs. The eggs hatch when exposed to sudden increases in temperature or moisture, such as when the animal grooms itself.

The larvae then enter the mouth, nose or other body opening and migrate to a location just beneath the skin where they cut a little hole so they can breathe and continue to develop. This development takes three to seven weeks, depending on the species of fly and host, and causes itchy swellings that range from half an inch to one inch in diameter.

After the larvae emerge from the skin, the lesions may become infected, but they normally heal without complication.

In gray squirrels, larvae are most abundant in late summer and fall, which is why people are seeing the lumps right now, Martin said. She said most of the squirrels will suffer no permanent effects from the parasites, however, a few may become debilitated by heavy infestations.

There is no safety threat to humans or pets from the hosts or their larvae. The presence of the larvae, however, often causes hunters to discard squirrels with warbles. This is an unfortunate waste of the resource, according to game managers, since the edibility of the squirrel meat generally is unaffected because the lesions are restricted to the skin. In most areas, including Florida, the small-game hunting season (this year Nov. 11 - March 4) occurs after the larvae have emerged from the hosts.

The FWC said the best thing to do if you see squirrels exhibiting these characteristics is simply to leave them alone and let nature take its course. Eventually the larvae will emerge and the squirrels will continue to go about the business of being squirrels.

More information about bot flies is available at http://botfly.ifas.ufl.edu/.