Opossum Under Your Deck on Long Island? Why It Usually Won't Stay, When It Will, and How We Get It Out (2026)

If you saw a cat sized gray animal with a pointed white face and a bare, rat like tail slip under the deck at night, it is an opossum. The Virginia opossum is New York's only marsupial and nothing else on Long Island looks like it. An adult runs about 28 inches long including a 9 to 13 inch hairless tail and weighs around 8 pounds, with big males up to 15. The fur is grizzled gray, the ears are thin and black, and the walk is a slow, flat footed waddle. If it stops and opens its mouth at you, you will see a lot of teeth: opossums have 50, more than any other mammal in the region.

If you did not see it, here is how to tell an opossum from the other deck dwellers. Raccoons are heavier, masked, and leave a chewed, torn mess around garbage and a strong latrine smell. Skunks dig a neat burrow with soil fanned out and leave cone shaped holes in the lawn. Opossums do neither. They rarely dig; they use whatever gap already exists under the lattice, and they drag in leaves, grass and shredded paper to bed down on. Their droppings are smooth, dark and about the size of a cat's, often left at the edge of the patio. The sound at night is the giveaway: an opossum hisses, growls and makes a sharp clicking noise, and a cornered one screeches. A rhythmic scratching inside a wall is not an opossum; see our guide to scratching noises in the walls at night for that.

One more clue that Long Island homeowners misread: an opossum out in the daytime is not automatically sick. In suburban areas they are seen by day, especially a mother foraging to feed a litter. Sick behavior looks like circling, stumbling, drooling or being unable to move away from you.

It is under your deck because the deck is dry, dark and close to food, and in most cases it will not stay long. Adult opossums are among the few mammals that keep no permanent home. They move between temporary dens, which include tree hollows, logs, abandoned burrows, sewers and buildings, and they den alone. A lone opossum that appeared under your deck this week is often somewhere else next week, which is why a "wait and watch" plan is reasonable for a single adult in mild weather, as long as the gap gets closed once it leaves.

Two situations change the timeline. The first is a mother with young. Opossums in our region breed twice a year, from January through late March and again from mid May into early July. A litter averages 6 to 9 babies, each the size of a honeybee at birth. They attach inside the pouch and nurse for 60 to 65 days, leave the pouch at about 70 days but keep riding on her back, and are independent at roughly 100 days. A female who has chosen your deck as the nursery will use it for the better part of two to three months, and she will defend it. On Long Island that means a den found in March or April, or in July and August, should be assumed to hold young until proven otherwise.

The second is cold. Opossums do not hibernate, but when temperatures fall to the mid teens or low 20s they stop moving and stay in a den for several days at a stretch, and groups of up to eight will share one winter den for warmth. A December opossum under your deck may be there through every cold spell until March, and it may not be alone.

So the honest answer is: days, if it is one adult in mild weather; months, if it is a nursery or a winter den. The visible clues that tip it toward months are nesting material being dragged in, the same animal coming and going nightly for more than a week, and the season.

Not very, but not harmless either. The real risks are a bite to a pet that corners it, fleas, and contamination of outdoor pet food and water. Rabies is the first thing people ask about, and the news is good: an opossum's body temperature is low enough that rabies is very difficult for it to contract, and confirmed cases are rare. It is still possible, and with Nassau County declaring rabies an imminent public health threat in July 2025 after 25 confirmed raccoon and feral cat cases in a year, and Suffolk confirming six rabid raccoons in 2025 in the Amityville area, any wild animal behaving strangely on Long Island should be reported to the county health department rather than handled.

The more common injury is to a dog or cat. A cornered opossum goes through a set routine: hissing, growling, clicking, baring 50 teeth, arching its back, and releasing a foul smelling greenish fluid from its anal glands. If that fails and it is grabbed, it bites hard. A dog that goes under the deck after one often comes out with a torn muzzle or ear, and the vet visit costs more than the removal. Keep dogs on a leash in the yard after dark while an opossum is denning, and keep cats in at night.

Opossums also carry fleas, which drop off in the nesting material under the deck and can end up on your pets. And because they are scavengers, they get into pet food and water bowls left outside, contaminating what your animals eat. None of this is cause for panic. It is cause to get the animal out and the gap closed in the right order.

No. The claim that one opossum eats 5,000 ticks a season is a myth, and it matters here because many Long Island homeowners leave an opossum under the deck on purpose, believing it is protecting the yard from Lyme disease. It is not.

The number traces to a 2009 laboratory study published in Proceedings of the Royal Society B. Researchers put about 100 larval blacklegged ticks on captive opossums, counted how many fed and dropped into the tray below after four days (an average of 3.5 per animal), and assumed the animals had groomed off and eaten all the rest. They then extrapolated that into thousands of ticks per week in the wild. The opossums were released without anyone checking their fur for the ticks that were supposedly eaten.

In 2021, wildlife biologists Cecilia Hennessy and Kaitlyn Hild tested that assumption directly. They examined the complete stomach contents of 32 wild Virginia opossums under a dissecting microscope and found no ticks and no tick body parts in any of them, while finding fleas, crickets, worms and plenty of other food. They also reviewed every published diet study of the species they could locate, 23 in all, and not one had ever reported ticks in an opossum's stomach or scat. Their conclusion: ticks are not a preferred food item for Virginia opossums. The old number still appears on plenty of websites, including some government ones, but the stomach contents are the evidence.

If ticks are the concern, an opossum under the deck is not the solution. Our guide to getting rid of ticks in your yard on Long Island covers what actually reduces them.

Neither. Sealing the gap with an opossum still under there and relocating a trapped one are the two shortcuts that create a bigger problem, and the second one is illegal in New York.

Start with sealing. An opossum that is shut in will try to dig or push out, and if it cannot, it dies under your deck, and a decomposing animal under boards is a smell that lasts for weeks with no easy way to reach the body. A mother sealed in dies with her litter. The twist with opossums is that you cannot judge "empty" by looking for a motionless animal. When badly frightened an opossum collapses into an involuntary faint, "playing possum," and can lie limp, teeth bared, for up to six hours. Homeowners have closed a lattice panel on an opossum they assumed was dead. Confirm the den is empty by watching the opening for activity over several nights, or by having it checked, before anything is closed.

Now the legal side, which surprises people. New York State DEC's rules for homeowners treat opossums differently from skunks and raccoons. A property owner may take an opossum that is damaging property, but an opossum that is merely a nuisance, meaning it is under your deck and annoying you but not destroying anything, requires a DEC permit to take. On top of that, DEC states plainly that it is illegal for you to move or relocate an animal off your property: you cannot live trap it and release it in a park, on state land, or anywhere other than the property where it was captured. If you take an animal outside the open hunting and trapping season, it must be buried or cremated immediately. The drive to the preserve with a trapped opossum in the back seat is the exact thing the law forbids. Transporting live wildlife requires a Nuisance Wildlife Control Operator license, and a signed agreement with a licensed operator is what makes the removal legal.

Mothballs and ammonia are the other common attempts. Mothballs are EPA regulated pesticides whose labels allow use only in sealed containers against fabric pests; placing them under a deck or using them to repel any animal violates the label and is illegal, and they do not move a denned opossum anyway. Bright light and noise under the deck can nudge a transient adult along. They do nothing for a nursing female.

This is the order we use on Long Island opossum jobs, whether the animal is under a deck, a shed, a porch or in a garage.

1. Confirm the animal and find every gap. We walk the full structure, not just the gap you noticed. Opossums do not dig their own entrance, so we are looking for existing openings under lattice, skirting and steps, plus dragged in leaves or paper that mark the bed. We also check for a second animal in cold weather.
2. Check the calendar for young. From March into April and from July into August we assume a litter may be present until we rule it out. If a female is carrying young, the plan is built around getting her and the litter out together rather than separating them.
3. Set the trap at the entrance. A box trap goes at the opening the opossum is using so it walks in on its normal route out at dusk. Opossums are slow and food driven, so a baited trap at the right gap works quickly.
4. Remove the animal under cover. A trapped opossum will hiss and show its teeth, which is theater. It is carried out covered and handled by a licensed operator, as New York law requires for transport.
5. Confirm empty, then close the opening with metal. Once we are sure nothing remains, we cover the gap with galvanized wire mesh anchored into the ground. If you want the whole deck skirted so nothing moves in next season, we will show you exactly how: half inch hardware cloth run 12 inches below grade and bent outward 12 inches in an L shape, which stops digging animals that might test the same spot later.

For an opossum that is only wandering the yard and not denning under anything, we run a 10 day exterior trapping program instead of the nesting removal.

A denning opossum is usually trapped within a few nights, because it leaves and returns through the same gap every evening and it is not a cautious animal. The 10 day exterior program for a yard opossum runs the full 10 days because a wandering animal is not on a fixed route. Sealing happens the day we confirm the space is empty.

Three things set the price, and we put it in writing before anyone comes out: where the animal is denning and how hard the opening is to reach, how many openings need closing, and whether young are present, which changes the handling and the timeline. Most jobs are quoted over the phone. Larger ones get a free on site look first. Nesting removal, meaning an opossum living under a structure, carries our 6 month written guarantee on that opening. The exterior trapping program has no guarantee, because we cannot promise which animals cross your yard after we leave.

The thing we will tell you up front: if pet food is left outside overnight, the opossum is there for the food, and closing the deck gap moves the problem to the garage or the shed. Fix the food and the gap together.

Take away the food, then take away the shelter, in that order. Opossums are opportunistic scavengers that eat dead animals, fruit, seeds, insects, eggs and whatever is in the garbage, and in suburbs they go straight for pet food, bird feeders and loose trash.

Food first. Bring pet food and water bowls in before dark every night. Use garbage cans with lids that latch, not lids that sit on top. Pick up fallen fruit under trees and clean up under bird feeders, where spilled seed draws opossums, mice and the rats that follow them. Keep the grill clean and the grease tray emptied.

Shelter second. Close the garage door at dusk; an open garage with a bag of dog food in it is the most common "opossum in my garage" call we get. Pull brush piles, stacked lumber and old patio furniture away from the house. Then skirt the deck: half inch galvanized hardware cloth fastened to the bottom rail, run 12 inches down into the soil and bent outward 12 inches in an L, then backfilled. The buried L is what stops a digging animal; lattice alone keeps out nothing. Trim branches that touch the roof as well, since opossums climb and will use a low roof to reach a soffit gap.

None of this requires a repellent. Granular and spray repellents fade with rain and an animal that has already found food ignores them. Removing what it came for is the part that lasts.