Droppings Under Your Deck: What Animal Is Denning There?

Droppings under a deck usually mean an animal is using the space as a den, not just passing through — most often a skunk, opossum, feral cat, or raccoon, and occasionally a groundhog. Skunk droppings are crumbly and full of shiny insect parts, opossum droppings are large and curved, cat droppings are often buried in loose soil, and a pile of tubular droppings in one corner is a raccoon latrine that needs professional-level caution. Timing matters: from spring into midsummer, most of these animals have babies down there.

Most likely causes

  • Skunk — 1–2 inch crumbly droppings full of shiny insect fragments, plus a faint musky odor
  • Opossum — large curved droppings, surprisingly dog-like for the animal's size
  • Feral or outdoor cat — droppings buried or half-buried in loose soil, strong litter-box smell
  • Raccoon — tubular blunt-ended droppings accumulating in one latrine corner
  • Groundhog — a wide burrow entrance with a soil fan, but droppings rarely visible (they defecate underground)

Compare the possible causes

Possible cause Key signs When it happens How likely
Skunk Tubular droppings 1–2 inches long that crumble easily and glitter with undigested insect shells, often near a 4–6 inch entry hole with a slight musky smell Denning is heaviest fall through early summer; babies are typically present May through July Very common
Opossum Large, smooth, often curved or tapered droppings up to 2–3 inches, sometimes deposited near the entrance, with no attempt to bury them Year-round, but individual opossums move on every few weeks; young ride with the mother spring through summer Common
Feral or outdoor cat Segmented droppings buried or scratched over in the loose dry soil under the deck, with a sharp ammonia or litter-box odor in the space Year-round; kittens most likely spring through early fall Common
Raccoon Tubular, blunt-ended droppings 2–3 inches long accumulating in one corner or along a joist — a latrine — often with berry seeds visible Year-round denning; babies are born March through May and stay for months Common
Groundhog A 10–12 inch wide burrow entrance with a fan of excavated soil, well-worn path, but few or no visible droppings Active spring through fall; hibernates in the burrow through winter Less common

Visual clues to check

  • Examine texture from a distance with a flashlight: crumbly and glittery with insect parts means skunk; smooth and dog-like means opossum
  • Look for burial: scratched-over soil mounds and an ammonia smell point to cats
  • Check for a repeat pile: droppings of different ages stacked in one corner is a raccoon latrine — stop and keep your distance
  • Measure the entry: a 4–6 inch hole suggests skunk; larger torn-open gaps suggest raccoon; a 10–12 inch hole with a soil fan means groundhog
  • Dust flour or sand at the entry in the evening and read the tracks at dawn — five-toed handprints are raccoon, small cat prints show no claws, skunk prints show long front claws
  • Sniff (from outside): persistent faint skunk musk or a litter-box odor each identifies its owner

The causes in detail

Skunk

Skunks are the most frequent under-deck tenants in much of the country because the space mimics their natural den sites. Their droppings give them away: crumbly texture and shiny insect fragments, since beetles and grubs make up much of their diet. You may also notice small cone-shaped holes in the lawn nearby from their nightly grub digging. A persistent faint skunk odor around the deck — without a full spray event — usually means one is living, not visiting.

Opossum

Opossum droppings are bigger than you'd expect from the animal and are the ones most often mistaken for a small dog's. The good news about opossums is that they're transient — they rotate between den sites and rarely stay under one deck more than a few weeks — and they're docile, eating ticks, grubs, and carrion as they go. Because mothers carry their young in a pouch and then on their back, an opossum eviction rarely strands babies the way a raccoon or skunk eviction can.

Feral or outdoor cat

Dry, sheltered soil under a deck is an irresistible litter box, and a feral cat may also den and have kittens there. Cats usually bury their waste, so look for scratched-over mounds rather than exposed droppings, plus the unmistakable smell. Cat feces can carry toxoplasmosis, so gloves are non-negotiable during cleanup, and pregnant women should stay out of the job entirely. If kittens are present, contact a local TNR (trap-neuter-return) group rather than blocking access.

Raccoon

Raccoons use communal latrines, so instead of scattered droppings you'll find a growing pile of different ages in one spot under or on the deck. This is the highest-stakes identification on this page: raccoon feces can carry raccoon roundworm eggs, which cause serious disease in people and pets, and the eggs persist in soil for years. Don't attempt DIY latrine cleanup in a crawl-height space — this combination of confined air, contaminated soil, and a defensive mother raccoon is exactly what wildlife professionals are for.

Groundhog

A groundhog under the deck announces itself with earthmoving, not droppings — groundhogs dig latrine chambers inside their burrows, so you'll almost never see their waste on the surface. The dropping-free burrow with a big soil apron is itself the diagnostic sign. The concern with groundhogs is undermining: an extensive burrow system can settle footings and slabs, so long-term residents are worth evicting even though the animal itself is harmless.

When to worry

  • A raccoon latrine forming under or on the deck — a roundworm hazard for children and pets
  • Chittering, mewing, or thumping sounds from below between March and July, which mean babies are down there
  • A skunk denning within reach of a curious dog — a spray or bite incident waiting to happen
  • Soil settling, a leaning post, or gaps opening along the deck edge above a groundhog burrow
  • Any resident animal that looks sick, moves erratically, or shows no fear of people — keep everyone away and call animal control

What to do now

  1. Identify the tenant first with droppings, tracks, and a dusk watch of the entry hole — every next step depends on the species and the season
  2. Assume babies from March through midsummer and wait if you can; evicting a mother then strands the litter under your deck, which becomes a worse problem
  3. Make the space unwelcoming: a bright work light, a radio on a talk station, and rags with apple cider vinegar near the entrance often persuade skunks and raccoons to relocate the family on their own
  4. Confirm everyone is out before excluding — stuff the entry loosely with newspaper or dust a flour patch and wait 48–72 hours of no disturbance
  5. Exclude permanently with 1/4- or 1/2-inch hardware cloth around the deck perimeter, buried 8–12 inches and flared outward in an L to stop diggers
  6. Handle a cat situation through a local TNR or rescue group, especially if kittens are present
  7. For a raccoon latrine, a stuck or orphaned litter, or an animal that won't leave, call a licensed wildlife control operator — many states restrict trapping and relocating wildlife yourself

What not to do

  • Don't seal the entry until you're certain no animal or babies remain — a trapped animal will die under the deck or tear its way out through your house skirting
  • Don't handle any droppings bare-handed, and don't dry-sweep or shovel a raccoon latrine
  • Don't crawl under the deck to confront the animal; a cornered skunk sprays and a mother raccoon defends
  • Don't use mothballs or ammonia-soaked rags in quantity — they're ineffective at safe doses and illegal as pesticides in many states
  • Don't trap and relocate the animal yourself; besides being illegal in many states, it often orphans a hidden litter

Think you know the suspect?

These animals commonly cause this clue — see their full sign profiles:

Frequently asked questions

How do I know if the animal is living under the deck or just passing through?

Look for commitment signs: a worn entry hole with smoothed edges, fresh tracks in dusted flour on consecutive nights, accumulating droppings, odor, and sounds. A passerby leaves one dropping and moves on; a denning animal produces fresh evidence every day. The newspaper test — loosely stuffing the entry and seeing if it's pushed out overnight — settles it in a day or two.

When is it safe to block the entrance?

Only after 48–72 hours with zero new activity, and ideally outside baby season. From March through midsummer, assume any denning skunk or raccoon has young that can't leave on their own. Wildlife operators often install a one-way door that lets the adult exit and not return, then verify the space is empty before sealing — the safest pattern to copy or hire out.

Will the animal damage my deck?

Skunks, opossums, and cats mostly just occupy the space; the real structural risk is a groundhog, whose burrow system can undermine footings and slabs over time. Raccoons are harder on the structure above — they tear at boards and screens. The bigger cost of waiting is usually contamination: months of droppings in the soil are unpleasant and, with raccoons, genuinely hazardous.

What smells or repellents actually make an animal leave?

No spray or granule reliably evicts a denning animal, and mothballs are both ineffective and illegal used that way. What works is making the den feel unsafe: light, noise, and human scent at the entrance for several nights running. Mothers usually move the litter themselves within a few days — then you exclude. If harassment fails after a week, that's the cue to call a professional.

Related yard clues

Animal Droppings Large Droppings in Your Yard: Raccoon, Coyote, Dog, or Fox? Large droppings in a yard usually come from raccoons, coyotes, neighborhood dogs, or foxes. Raccoon droppings are tubular with blunt ends and often accumulate in one repeated spot called a latrine; coyote droppings are rope-like and tapered with visible fur, bone, or seeds; fox droppings are smaller, twisted, and pointed at the ends. A raccoon latrine deserves special caution because of raccoon roundworm. Read the guide → Animal Droppings Tubular Droppings in the Garden: Raccoon, Opossum, or Skunk? Tubular droppings in a garden bed most often come from raccoons, opossums, or skunks raiding for produce, grubs, and insects — though garter snakes and even toads leave surprisingly substantial droppings too. Blunt ends and berry seeds point to raccoon, tapered curves to opossum, and a crumbly texture full of shiny insect parts to skunk. Because raccoon droppings can carry roundworm eggs, droppings in a food garden also raise a produce-safety question worth taking seriously. Read the guide → Animal Droppings Droppings in the Garage: Mouse, Rat, Bat, or Squirrel? Droppings in a garage are most often from mice, with rats, bats, and squirrels as the other usual suspects. Mouse droppings are 1/4-inch pellets with pointed ends scattered along walls and shelves; rat droppings are two to three times larger with blunt ends; bat droppings pile up in one spot beneath a roost near the ceiling or wall top. Before you identify anything, know the cleanup rule: never sweep or vacuum rodent droppings dry. Read the guide →

Still not sure? Compare with these clues

Yard Holes Holes Under the Fence: What's Digging In (or Out)? A hole under a fence is usually a travel gap scraped out by rabbits, skunks, or a neighborhood dog — or the edge of a real burrow if a groundhog has moved in along the fence line. The key distinction is pass-through versus home: a shallow trench under the boards means something is commuting through your yard, while a deep hole with a big dirt pile means something is living there. Read the guide → Yard Holes Holes Near Your Foundation: Causes and When to Act Holes right along a foundation usually come from chipmunks, Norway rats, or voles, all of which like the shelter a house wall provides — but water pouring from downspouts and settling backfill soil carve foundation-line holes too. Sorting burrow from washout matters, because a rat burrow against the house is the one that needs fast professional attention. Read the guide → Tracks, Nests & Outdoor Clues Small Animal Tracks in Your Yard: How to Read Them Small animal tracks in your yard most often belong to rabbits, squirrels, raccoons, opossums, skunks, or a neighborhood cat or dog. Counting the toes, checking whether claw marks show, and looking at how the prints are grouped will identify the visitor faster than the shape of any single print. Read the guide → Yard Holes Large Holes in Yard: Groundhog, Fox, Skunk, or Armadillo? A hole 6 inches across or bigger is a den entrance, and in most American yards the owner is a groundhog — an 8- to 12-inch hole with a big dirt mound is their signature. Foxes, armadillos, and skunks dig or borrow similar burrows, especially under sheds, decks, and porches, so smell, mound size, and location are what separate them. Never fill a large hole until you know it's empty. Read the guide →