The short version
Rodent control in Fort Collins, CO starts with sealing before the September to November push, when cold nights near the 17F winter average send deer mice and house mice indoors. Close gaps of 1/4 inch, trap inside, and treat every dropping as a possible hantavirus source: air the space out, soak with bleach, and never sweep. Norway rats matter most around food waste.
- Fort Collins has deer mice, house mice and Norway rats; deer mice carry hantavirus.
- Colorado logged 2 provisional hantavirus cases in 2025, per CDC weekly tables.
- Indoor moves peak September through November as nights get cold.
- Dry air pushes rodents toward indoor water near sinks, water heaters and pet bowls.
- Clean droppings wet after 30 minutes of airing out, and never vacuum them.
This page is for Fort Collins homeowners finding droppings in the garage, basement or a stored camper, renters near Colorado State University dealing with mice, and anyone running a brewery, restaurant or food business worried about rodents around grain and waste. It also helps if you are about to clean out a shed or outbuilding that sat closed all winter.
What to look for
Three rodents cause most of the trouble in Fort Collins. Deer mice, with their white bellies and two-tone tails, live in grasslands, field edges and open space and readily move into garages, sheds, campers and basements. They are the main hantavirus carrier in the western United States. House mice are the familiar gray indoor mouse, nesting in walls, cabinets and stored items. Norway rats are larger burrowers that follow food and water, often around dumpsters, compost and commercial kitchens. The semi-arid climate changes how these animals behave. Fort Collins gets only about 16 inches of precipitation a year, and average humidity is around 53 percent, so outdoor water is scarce for much of the year. Rodents are drawn to irrigation, pet water, leaky hose bibs, and once indoors, the moisture around sinks, dishwashers and water heaters. Summers near 87F keep breeding going outdoors, and cold winters with lows around 17F make indoor shelter the obvious choice by late fall.
- 1Small droppings in the garage, along basement walls or in kitchen drawers.
- 2Nests made of shredded paper, insulation or fabric in stored boxes, campers or outdoor gear.
- 3Chewed seed bags, pet food or birdseed in the garage or shed.
- 4Droppings and nesting material under the hood or in the cabin of a vehicle parked outside.
- 5Scratching inside walls or ceilings at night once cold weather sets in.
- 6Burrows near dumpsters, compost piles or along foundations, a sign of Norway rats.
- 7A musty, ammonia smell in a closed garage, shed or crawlspace.
Why it’s worth acting soon
- Deer mouse droppings accumulate in closed spaces, increasing hantavirus exposure during cleanup.
- Mice chew vehicle wiring, appliance cords and house wiring, which can be costly to repair.
- House mice breed through winter indoors, so a few in October can be many by spring.
- Norway rats around food businesses can lead to contamination and inspection problems.
- Soiled insulation in attics or crawlspaces has to be removed and replaced.
94%Share of U.S. hantavirus cases west of the Mississippi since 1993CDC 7Average U.S. human plague cases per yearCDC Treatment options and typical costs
Fall exclusion
Quoted after inspection
Gaps at garage doors, foundation cracks, window wells, utility penetrations and crawlspace vents are sealed with steel wool, hardware cloth, flashing and sealant. Done in August or early September, it stops the yearly fall entry before cold nights push mice inside.
- Time
- One to two days
- Best for
- Homes with mice every fall
Snap trapping indoors
Quoted after inspection
Traps along walls, in garages and in basements remove mice already inside. Snap traps are preferred over live traps for deer mice, because live-catching means more handling of an animal that may carry hantavirus.
- Time
- One to three weeks
- Best for
- Active mice in living spaces, garages and basements
Exterior station program for rats
Quoted after inspection
Locked stations along foundations, fences and dumpster areas hold traps or labeled bait for Norway rats. Placement follows the activity found during inspection, and regular service keeps stations working. This suits restaurants, breweries and homes near commercial areas.
- Time
- Monthly or more often for businesses
- Best for
- Food businesses and properties with rat activity
Hantavirus-safe cleanup
Quoted after inspection
Garages, sheds, campers and crawlspaces with droppings are ventilated, wetted with bleach solution and cleaned without sweeping. Heavily soiled insulation or nesting material is bagged and removed with respiratory protection.
- Time
- One visit, more for large spaces
- Best for
- Closed outbuildings and stored vehicles
Prices are typical published ranges. Ask what’s included before you compare quotes.
Under the sink is the first place to check: the hole where the pipe passes through the cabinet back is often cut much bigger than the pipe.Why dry Fort Collins air still sends rodents indoors.
Then comes the cold. Winter lows average about 17F at this elevation, and when fall nights start dropping, deer mice and house mice look for a warm place to settle. September through November is the peak entry season. The practical response is twofold. Fix leaks and remove outdoor water sources near the foundation. Then seal entry points, especially at garage doors, window wells and utility penetrations, before the cold arrives. A house that is both dry and sealed gives rodents little reason to move in. People often expect fewer rodents in a dry place, but Fort Collins shows why that is not the case. The city gets only about 16 inches of precipitation a year, and average humidity is around 53 percent. Outdoors, water is scarce for long stretches. Rodents need water, and they find it near people. Irrigated lawns, leaky hose bibs, pet bowls, bird baths and window wells that collect runoff all draw them close to the house. Once inside, the space under sinks, behind dishwashers and around water heaters offers both moisture and shelter.
Deer mice and hantavirus in Colorado: garages, sheds and campers.
Prop the doors open and give the space a half hour of fresh air first. With gloves on, saturate each pile of droppings and every nest using 1.5 cups of bleach in a gallon of water. After a five-minute soak, paper towels pick it all up, and it goes straight into a sealed bag. A broom or shop vacuum does the opposite and puts the particles in the air. For campers, check cabinets, mattresses, vents and engine compartments. For sheds and garages, look in boxes, under shelving and in stored gear. If contamination is heavy, hire a crew with respirators. Deer mice are common in Colorado and are the main hantavirus carrier in the West. The CDC's provisional count lists 2 Colorado cases in 2025, and nationally the disease is fatal in about 35 percent of cases. That makes cleanup the most important part of any rodent job in Fort Collins. Exposure happens when people breathe in particles from dried droppings, urine or nests. The usual setting is a closed space: a garage in spring, a shed that has not been opened in months, a camper or trailer pulled out for the season, or a crawlspace. Keeping everything wet is what protects you.
A metal vent cover with a working flap keeps mice out all winter. Plastic flaps crack in the cold and get chewed open.Grain, hops and food waste: rodent control for Fort Collins breweries and restaurants.
Rats forage widely, so a messy dumpster can draw them from a distance. Seal the building. Loading doors, utility penetrations and gaps around pipes need the same 1/4-inch standard as homes. Door sweeps on back doors matter. Most food businesses benefit from a regular service schedule with exterior stations and interior monitoring. Ask a provider how often they will visit, what records they keep, and how they will report activity. Good records help during health inspections and show trends before they turn into problems. Fort Collins is known for craft breweries, and any business that stores grain or handles food waste has to think about rodents. Norway rats and house mice are drawn to malt, spent grain, spilled ingredients and open dumpsters. Start with storage. Keep grain and dry ingredients in sealed metal or heavy plastic containers, off the floor and away from walls so you can see droppings. Clean up spills promptly, especially around mills and loading areas. Manage waste carefully. Keep dumpster lids closed, clean the area around dumpsters regularly, and move spent grain off-site quickly.
A month-by-month look at rodents in Fort Collins.
As nights cool, mice test garage doors, window wells and foundation gaps. Many get in during October. December through March brings winter lows around 17F. Mice that made it inside nest in walls, basements and garages and keep breeding. Trapping is most effective during this indoor period. The takeaway for Fort Collins homeowners: seal in August, trap in fall and winter, and clean carefully in spring. Following that order keeps the cycle from repeating every year. Fort Collins rodents follow a clear seasonal pattern tied to the cold. From April through June, deer mice and house mice breed outdoors in fields, gardens and open space. This is also when people open garages, sheds and campers after winter, so spring cleanup is a common hantavirus exposure moment. July and August are warm, with highs near 87F, and outdoor populations peak. This is the best time to seal, because rodents have not started pushing inside yet. September through November is the main entry season.
What a fair rodent quote looks like for a Fort Collins home.
Cleanup should be spelled out. Ask whether droppings and nesting material will be removed, how, and with what protective equipment. If insulation needs replacing, that is often a separate line. With a median home value near $540,000, the wiring, ductwork and insulation at stake are worth protecting, and sealing a house properly takes time. A higher quote that covers real sealing usually costs less over time than a cheap one that only sets traps. Ask what happens if mice return within a set period, and get it in writing. A good rodent quote is specific about sealing. It lists the entry points found, such as garage door gaps, window wells, foundation cracks and utility penetrations, and says what material will be used on each. Rodents chew through foam used by itself, so look for steel wool, mesh and sheet metal on the materials list. The quote should also say how many follow-up visits are included for trapping and how long the provider expects trapping to take. For Fort Collins homes, ask specifically whether outbuildings, detached garages and stored campers are part of the inspection, since deer mice often live there.
What affects the price
- Number of entry points, especially around garage doors, window wells and utility lines.
- Whether the problem involves deer mice in outbuildings, which adds careful cleanup.
- How many structures are included, such as detached garages, sheds or campers.
- Amount of contaminated insulation or nesting material to remove.
- Whether a business needs an ongoing service schedule.
- Number of follow-up trap checks included.
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What's your biggest concern about rodents?
When to call for help
Call for help if you find heavy droppings in a closed space like a shed, garage or camper, since that is the classic hantavirus exposure setting. Bring in a professional too if mice keep turning up after a couple of weeks of trapping, if you have rats, or if rodents have chewed wiring. Food businesses in Fort Collins should not wait at all after seeing rodent signs. For homeowners, the best time to call is late summer, before the fall push.
What you can do yourself
Never sweep or vacuum. A few droppings on a garage shelf is a fine DIY job done that way. A shed, camper or crawlspace with heavy contamination is better hired out. Professionals earn their fee when the entry points are hard to find or reach, when rats are involved, or when a business needs ongoing service. They can inspect the full foundation, window wells and roofline, and they know how to place any bait in locked stations following the label. DIY works for a few house mice in an accessible space. Set snap traps along walls where you see droppings, seal small gaps with steel wool and sealant, and check the garage door seal. Many homeowners handle that well. Deer mice raise the stakes on cleanup, not trapping. The CDC routine is short: half an hour of open doors, gloves on, a bleach soak that sits for 5 minutes, then paper towels into a sealed bag.
Rodents in Fort Collins
Colorado reported 2 provisional hantavirus cases in 2025, and deer mice are part of the local picture. Fort Collins was founded in 1864, so homes span many eras, and a median home value near $540,000 makes protecting wiring and insulation worthwhile. The university brings rentals with frequent turnover. The breweries and restaurants add grain, spent mash and food waste that can attract Norway rats if not managed. Summers reach around 87F, and winter lows average about 17F, which drives a strong fall entry season from September through November. Average humidity sits near 53 percent and yearly precipitation is only about 16 inches, so water is scarce outdoors, and rodents follow irrigation, leaks and indoor moisture. The semi-arid climate defines its rodent issues. Fort Collins is an urban city of about 170,000 people at an elevation of about 5,003 feet, known for Colorado State University and its craft breweries.
Local research
Rodents in Fort Collins, CO: what the public record shows
Before you compare quotes, it helps to know which rodents actually live in Colorado, when they are busiest around Fort Collins, and what the state figures look like. Everything below links to the agency or university page it came from.
Rodent species recorded in Colorado
- House mouse (Mus musculus) — Enters at 1/4 inch; 5-10 litters per year; eats about 200 small meals a night.
- Norway rat (Rattus norvegicus) — Burrowing rat of basements, sewers and ground floors; tail shorter than head plus body.
- Deer mouse (Peromyscus maniculatus) — Primary U.S. hantavirus carrier; lives throughout Washington and the interior West.
When rodents are busiest around Fort Collins
Fall entry (Sept-Nov). Norway rats and house mice move indoors as temperatures drop.
Based on Fort Collins’s semi-arid climate profile.
For context, nationally
- 1/4 inch (the width of a pencil) — Smallest gap a mouse can enter. CDC
- 890; 35% fatal; 94% west of the Mississippi — Hantavirus cases reported since 1993 (through 2023). CDC
Sources: CDC National Notifiable Diseases Surveillance System; CDC; Pest Notes: House Mouse; Pest Notes: Rats; Hantavirus. Figures are quoted as the source prints them. How we check our sources
Simple ways to keep rodents away
- Replace garage door bottom seals and side weatherstripping before September.
- Cover window wells with sturdy covers and seal gaps where wells meet the foundation.
- Fix leaky hose bibs and keep pet water inside at night, since water is scarce outdoors here.
- Store birdseed, grass seed and pet food in metal or heavy plastic bins.
- Keep campers, trailers and stored vehicles away from tall grass and check them monthly.
- Seal gaps around utility lines and dryer vents with steel wool and sealant.
- Keep firewood off the ground and away from the house.
- Businesses should keep dumpster lids closed and clean up spilled grain promptly.
After sealing, a few monitors or unset traps left along the walls tell you whether anything is still getting in before you hear it again.Did you know?
Colorado and Arizona together accounted for 5 of the 17 provisional U.S. hantavirus cases reported for 2025.
A quarter-inch hole is enough for a mouse, and the CDC notes rats can gnaw small holes until they fit.
U.S. human plague cases range from none to 17 in a given year, with fleas from wild rodents as the carrier.
Questions people ask
Are deer mice in Fort Collins dangerous?
Wet cleanup with bleach after airing the space out keeps the risk low. For Fort Collins homes, sheds, garages and stored campers are the common risk spots. The virus spreads through particles from dried droppings, urine and nests, usually when someone sweeps out a closed space. They can be, because deer mice carry hantavirus.
How many hantavirus cases does Colorado have?
Cases are rare, but the disease is serious, so careful cleanup is worth the effort. cases have been west of the Mississippi. Since 1993, about 94 percent of the 890 U.S. The CDC's provisional count for 2025 lists 2 hantavirus cases in Colorado, out of 17 nationwide.
When do mice come into Fort Collins houses?
Mice that get in during fall will stay and breed through winter, so sealing in August makes the biggest difference. As nights cool toward Fort Collins' 17F winter average, deer mice and house mice look for warm shelter, and garages and basements are easy targets. Mostly September through November.
Why do I have mice when Fort Collins is so dry?
Fixing leaks and sealing gaps both help. Cold weather does the rest. With about 16 inches of precipitation a year, outdoor water is limited, and rodents are drawn to indoor moisture near sinks, dishwashers, water heaters and pet bowls. The dry climate actually helps push mice inside.
Are there rats in Fort Collins?
Locked exterior stations and good sanitation are the main tools. Look for burrows near foundations and larger droppings. Rats show up most around food waste, dumpsters, compost and commercial kitchens. Norway rats are on Colorado's species list alongside deer mice and house mice, so Fort Collins properties can see them.
How do I clean mouse droppings out of a camper or car?
Check engine compartments for nests and chewed wiring. Never vacuum. Let it soak 5 minutes, then wipe up with paper towels and bag everything. Wear gloves and spray droppings and nests with 1.5 cups of bleach per gallon of water. Open all doors and windows and let it air out for 30 minutes.
Is plague a concern in northern Colorado?
Keep pets on flea control and avoid handling dead rodents with bare hands. Fleas from wild rodents spread it. The CDC averages about 7 human cases a year nationally, mostly in northern New Mexico, northern Arizona, southern Colorado and parts of California, Oregon and Nevada. Plague is rare.
Can a mouse get through a gap in my garage door?
Replace seals before fall and check the corners for daylight. Worn bottom seals and gaps at the corners where the door meets the frame are common entry points in Fort Collins garages. Yes, if the gap is about 1/4 inch or more, which is all the CDC says a mouse needs.
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Sources (6)
The facts in this article come from the public sources listed above. Every home is different, so ask the company you talk to about pricing and what’s included. Published by Rodent Exterminator · Updated October 11, 2026 · How we write these guides