The Opossum Under Your Deck or Crawl Space in Conway, SC

Or is it something else?

A very large rat. This is the mix up that gets an animal killed for no reason, usually at night at the edge of a flashlight beam. An opossum is far bigger than any rat found in South Carolina, closer to a cat in bulk, and the muzzle is long, pale and pointed rather than blunt and dark. The tail settles it: a roof rat's tail is thin, dark and scaly and stays roughly the length of the body, whereas an opossum's is pale, thick at the base and often dragged along the ground. Behavior finishes the job. A rat runs. An opossum tends to freeze, open its mouth wide and hiss, and if pushed it collapses on its side and plays dead.

What treatment actually involves

Because this animal is transient, the first job is working out whether anything is still living under there, and that takes patience rather than equipment. A patch of sifted sand or flour at the opening reads the traffic overnight, a camera on the gap for two nights shows how many and at what hour, and a look inside with a light shows whether there is a resting spot or a real den. Where a female is present she may be carrying young on her back or in the pouch, and that has to be established before anything is closed, because sealing a gap on top of dependent young leaves a dead animal under the floor and a smell that lasts through a summer.

Once the space is confirmed empty the work is carpentry, not chemistry. A one way door on the gap for a few nights guarantees it, then the perimeter gets closed properly: heavy galvanized screen along the deck or shed line, taken down into the soil and bent away from the wall so digging along the edge fails, crawl space vents rescreened in metal, the access door refitted with a latch, and lattice repaired rather than propped back. Trapping is usually the wrong opening move here for two reasons. State law limits what can be done with a captured furbearer, so it is not the gentle option people imagine, and an empty den in a yard with an open gap simply gets filled by the next animal. Closing the gap solves it once.

What they leave behind

Compared with a raccoon this is light work, and saying so is more useful than inflating it. There is rarely any structural damage at all, because an opossum uses an existing opening instead of making one. What you get is fouling in a confined space: droppings and urine on the vapor barrier or the soil, a flattened area of insulation, sometimes a batt pulled down from between the joists where it made a bed. On a screened porch or under a deck it is droppings on the slab and a musky smell that lingers in still air. The cleanup is bagging the waste, cutting out and replacing any insulation that got wet, and treating the area with a disinfectant and a deodorizer so the scent stops reading as an invitation. The one thing that turns a small job into an expensive one is a sealed entrance with an animal behind it, because then somebody has to open the floor or the deck to find and remove a carcass, and the odor and the flies will have moved into the living space by the time anyone gets to it.

Where DIY works and where it does not

Most of this is genuinely a homeowner job and it is cheap. Skirt the open side of a deck, refit lattice, screen crawl space vents with galvanized mesh rather than the flimsy aluminum insect screen that came with the house, latch the crawl space door, bring pet bowls in at night, clip the bin lids and clear brush and woodpiles off the foundation. Pick fallen fruit up. The two things not to do are backfilling or sealing a gap while something is still inside, and crawling under a deck to look, because a cornered animal that cannot leave will defend itself and there is no reason to put a hand into that space when a camera answers the question.

Whether you need to worry

Modest, and worth stating accurately rather than dramatically. Opossums are only very rarely found to be rabid, which is generally attributed to their low body temperature, so they are not the animal on this page that public health worries about. That does not make a bite trivial, and any bite or scratch from a wild mammal gets medical advice the same day. The practical issues are more ordinary. They carry fleas and ticks into a yard, so check the dog after a den has been active nearby, and their droppings and urine on a crawl space vapor barrier are handled with gloves and a mask rather than bare hands, the same as any other animal waste under a floor. The worst outcome is an animal dying in an inaccessible spot after somebody sealed the entrance, which brings blowflies and an odor that works up through floor penetrations for weeks.