SQUIRRELS ARE NOT GOING NUTS
September 8, 2003
“There’s a squirrel in my yard with lumps all over its body and it’s jumping in the air, rolling on the ground and acting like a crazy thing. What’s wrong with it?” asked a recent caller to the Florida Fish and Wildlife Conservation Commission’s (FWC) regional office.
Although squirrels might be acting a little, well, squirrelly this time of year, biologists say it’s really nothing to get alarmed about.
“When people call they describe these unusual antics, as well as large lumps on the squirrel’s body that appear to be cancerous tumors,” said Joy Hill, FWC’s public information coordinator for the Northeast Region. “The good news is, the lumps are not malignant tumors. In fact, they are caused by warbles, which are bot fly larvae growing just under the squirrel’s skin.”
In fact, once the larvae emerge, the squirrel generally recovers without further incident. But while the insects are burrowed under the skin, they are a real annoyance to the squirrel.
“In the Southeast United States, gray squirrels and other rodents, and rabbits, are commonly affected by bot fly warbles. Horses and cattle are sometimes affected by them too,” said Hill.
What happens is the adult female bot fly buzzes around the host animal’s nest or den and deposits its eggs there. When the unsuspecting squirrel or rabbit comes into the den to sleep or groom itself, its body heat and moisture cause the eggs to hatch. The newly hatched larvae then crawl into the critter’s mouth, nose or other body opening, and migrate to a comfortable spot just below the skin where they cut a little breathing hole and continue to develop. Depending upon the species of fly and host, this development process takes from three to seven weeks and causes itchy swellings that range from ½-inch to 1-inch in diameter.
After the larvae emerge from beneath the skin, the lesions may become infected, but they normally heal without complication.
“In gray squirrels, the larvae are most abundant in the late summer and early fall. This is why people are seeing the lumps and nutty behavior right now,” said Hill. “A few squirrels may become debilitated if they are heavily infested, but most will suffer no permanent effects from the parasite.”
In terms of health issues, there is no threat to humans or pets from the larvae itself or the affected animals; however, hunters often discard squirrels with warbles because they think they are diseased.
“This is an unfortunate waste of the resource, since the lesions are restricted to the skin and don’t affect the meat,” said Hill. “However, in order to avoid this waste, most states, including Florida, intentionally set the squirrel hunting season to occur after the larvae have emerged from the host animals.”
The best thing to do if you see these odd-acting squirrels is to simply leave them alone and let nature take its course. Eventually the larvae will emerge, the lesions will heal and the squirrels will go about the business of being squirrels.
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