A Snake in the Garage or Basement This Fall: What Colorado Homeowners Should Know
Colorado State University Extension says snakes may take shelter under and possibly inside buildings, and that this becomes more noticeable in fall as they look for a place to spend the winter. This guide covers what that means for your garage, basement, or crawl space, and what to do if you find one.
Why snakes turn up indoors in the fall
In summer a snake in the yard is a surprise. In late September, a snake curled behind the water heater or along the garage wall is more of a pattern. Colorado State University Extension's guide to coping with snakes says snakes need cool, damp shelter, may take up residence under and possibly inside buildings, and that behavior may become more noticeable in fall, when they look for places to hibernate for the winter.
Colorado's snakes spend the cold months tucked away. Colorado Parks and Wildlife says prairie rattlesnakes shelter in winter dens during the coldest part of the year, often in rodent burrows or rock crevices, and usually resume activity in late March or early April. The North American racer, CPW notes, hibernates in deep rock crevices, sometimes beneath buildings or in structures, and may share a winter site with other snake species.
The snake in your garage is most likely looking for a winter address, and a crack in your foundation or a gap under the door looks a lot like a rock crevice from its point of view.
Who might be in your garage
CSU counts 25 snake species in Colorado, and both CSU and Colorado Parks and Wildlife agree that the only venomous snakes in the state are rattlesnakes. Along the Front Range and the eastern plains, the snakes that can turn up around a house include:
- Garter snakes. The plains garter snake, according to CPW, is extremely cold tolerant and often strays far from water into residential areas. It lives mainly below 6,000 feet, though it reaches foothill canyons.
- Bullsnakes. CPW describes the bullsnake as a constrictor found in rural and outlying suburban residential areas, and as one of the most effective rodent control animals in the state. It also imitates a rattlesnake's coiling when threatened, which CPW says sometimes gets bullsnakes killed by people who think they are dangerous.
- Racers. Nonvenomous, and as noted above, sometimes willing to overwinter beneath buildings.
- Prairie rattlesnakes. CPW describes them as living in virtually every land habitat in their range, from plains grassland to foothill woodland. Homes that back onto open space share that habitat. This is the one to take seriously.
A fall detail worth knowing: CPW says prairie rattlesnake females give birth between late August and early October. A small snake in the garage in September is not automatically a harmless one. Small snakes are also harder to identify at a glance, so give a little one the same room you would give a big one.
What to do in the first few minutes
Two goals matter here. Nobody gets hurt, and you keep track of the snake.
- Back off. CPW's advice for rattlesnakes is to put at least five feet between you and the snake. For any snake you cannot identify, treat it as if it could be one.
- Get kids and pets out of the garage or basement and close the door behind them.
- Keep an eye on where it goes, from a safe distance. Knowing whether it slid under a shelf or into a wall gap saves a lot of searching later.
- Do not try to catch, kill, or move it. CPW is direct on this: never, under any circumstances, try to catch, kill, provoke, or move a rattlesnake.
- Call for help. If anyone is bitten, call 911 right away.
Colorado law does give people some room here. CPW says a person may relocate a rattlesnake for the safety of the animal or people, and one found in a house, building, or similar structure may be moved to an unconfined nearby location. That permission is not a recommendation to try it. Our snake removal team handles these calls so you do not have to.
How they get in
Snakes use gaps that are already there, and they do not need much room. CSU recommends sealing every opening a quarter inch or larger to keep snakes out of basements and crawl spaces.
The usual suspects around a Colorado garage or basement:
- The bottom seal of the garage door, especially torn or curled corners
- Gaps where the garage slab meets the foundation wall
- Utility penetrations for water, gas, cable, and the dryer vent
- Crawl space vents with missing or damaged covers
- Cracks in foundation walls and around basement window wells
- Gaps under exterior doors into the garage or basement
Walk the outside of the house at ground level and look for anything you could slide a pencil into. That is roughly the scale that matters.
The rodent connection
Snakes go where the food is. CPW calls the bullsnake one of the best rodent controllers in the state, and says prairie rattlesnakes often hibernate in rodent burrows. A garage with mice, or a woodpile with pack rats, is a garage that interests snakes.
That is why fixing a snake problem often means fixing a rodent problem too. If you are finding droppings, chewed boxes, or nesting material in the garage, deal with those at the same time. Our post on pack rats in garages and engine bays covers one rodent that nests in Colorado garages and engine bays.
Seal after the snake is out, not before
It is tempting to find the gap and close it right away. The catch is that a snake settling in for winter may already be inside, behind a shelf, in a wall void, or in a crawl space. Sealing the opening then traps it indoors for the season.
The order that works:
- Confirm the space is clear, or have any snake that is present removed.
- Walk the full exterior at ground level and mark every opening a quarter inch or larger.
- Seal those openings with the materials CSU lists: mortar, caulking compound, expanding foam, or 1/8-inch hardware cloth, choosing what fits each gap.
- Replace worn garage door seals and door sweeps.
Colorado Wildlife Specialists offers inspection, exclusion, and consultation for snake problems, and we follow Colorado Parks and Wildlife rules on every job.
Make the outside less inviting
The last piece is the yard. CSU recommends removing brush and rock piles and controlling rodents to discourage snakes from living near the house. CPW notes that prairie rattlesnakes take shelter in crevices, woodpiles, brushy vegetation, and mammal burrows.
A few practical steps before winter:
- Move firewood and lumber stacks away from the foundation and off the ground
- Clear brush, rock piles, and tall weeds from the strip right next to the house
- Store birdseed, pet food, and grass seed in sealed containers so rodents are not drawn in
- Keep the garage door closed when nobody is working in there
None of this means Colorado's snakes are the enemy. Most of them are harmless, and some eat the rodents you would rather not have. They just do not belong in the basement. If you have found one inside this fall, or you want the gaps found before one moves in, contact us and we will take it from there.
Frequently asked questions
Will a snake in my basement or garage leave on its own?
Sometimes, but in fall you should not count on it. Colorado State University Extension says snakes look for places to hibernate in fall and may settle under or inside buildings. A snake that has found a sheltered, cool spot may stay put. It is safer to have it removed and then find and close the gap it used.
Is a small snake in the garage safe to pick up?
Do not assume so. Colorado Parks and Wildlife says prairie rattlesnakes give birth between late August and early October, so young rattlesnakes are out during the same weeks snakes start looking for winter shelter. Give a small snake the same caution as a large one and keep your distance from any snake you cannot identify with certainty.
Can I move a rattlesnake out of my garage myself?
Colorado Parks and Wildlife says a person may move a rattlesnake found in a house, building, or similar structure to an unconfined nearby location. The same agency's safety advice is to never try to catch, kill, provoke, or move a rattlesnake yourself. Keep at least five feet away, keep people and pets clear, and call a professional. If anyone is bitten, call 911.
What size gap can a snake get through?
Small ones. CSU Extension recommends sealing all openings a quarter inch or larger to keep snakes out of basements and crawl spaces, using mortar, caulk, expanding foam, or 1/8-inch hardware cloth. That is why a garage door seal with a torn corner or an unsealed utility line can be enough.
Related reading
Found a snake inside this fall?
Keep your distance and give us a call. We handle removal and help close the way in.