Rats live on every continent except Antarctica, and their distribution is almost entirely a byproduct of human settlement rather than wild habitat preference. The two dominant species divide the world by lifestyle: Norway rats (Rattus norvegicus) dominate temperate cities, sewers, and ports worldwide, while roof rats (Rattus rattus) dominate warmer coastal and tropical regions and climb rather than burrow. Where people store food and build shelter, rats follow within a few hundred feet. Their range ends only where winters drop below roughly 20°F for extended periods, where water is absent, or where humans have deliberately eradicated them, as on Alberta's rat-free zone.
The Two Rat Species and Their Separate Maps
A map of where rats live is really two overlapping maps. Norway rats and roof rats are different animals with different geography, and confusing them is the most common error in pest reporting.
Norway rats are burrowers. They live at ground level, in sewers, basements, and rubble, and they tolerate cold far better than their cousins. Their range covers most of Europe, North America, and temperate Asia, plus port cities on every continent except Antarctica. They cannot climb well and rarely go above the first floor of a building.
Roof rats are climbers. They nest in attics, palms, vines, and warehouse rafters, and they are cold-sensitive. Their range is concentrated in a band roughly 35 degrees north to 35 degrees south of the equator: the Mediterranean, coastal Africa, India, Southeast Asia, and the southern United States. In the US, roof rats dominate the Gulf states and California coast, while Norway rats dominate the northern interior.
In plain terms: cold cities get Norway rats in the basement, warm cities get roof rats in the attic, and many port cities get both.
Why Rats Follow Humans, Not Wilderness
Rats are not wilderness animals. Both species are commensal, meaning they live at human expense, and their global spread tracks shipping routes and grain storage more closely than climate alone.
The mechanism is food predictability. A wild rodent must forage across large areas and faces variable supply. A city rat finds a fixed, dense, year-round food source: garbage, grain, pet food, and sewage. This allows population densities two to three orders of magnitude higher than wild rodent populations. A single city block can support more rats than a square mile of forest supports mice.
Shelter works the same way. Buildings provide stable temperature, dry nesting space, and unlimited burrow sites in foundations and walls. The result is that rat range is bounded less by ecology than by infrastructure. Remove the food and shelter and the rats leave or die; add them and rats appear, often within one breeding season.
Quantified Comparison: Norway Rat vs. Roof Rat
The table below compares the two species on the traits that determine where each one lives. Values are typical adult ranges, not extremes.
| Trait | Norway rat | Roof rat |
|---|---|---|
| Scientific name | Rattus norvegicus | Rattus rattus |
| Adult body weight | 12–18 oz | 5–9 oz |
| Body length (nose to tail tip) | 16–20 in | 14–18 in |
| Tail relative to body | Shorter than head plus body | Longer than head plus body |
| Cold tolerance | High; survives freezing winters | Low; needs warmth above 40°F |
| Preferred elevation | Ground, sewers, basements | Attics, rafters, trees, upper floors |
| Typical litter size | 8–12 pups | 5–8 pups |
| Litters per year | 4–7 | 3–5 |
| Typical home range | 100–150 ft from nest | 100–300 ft, often vertical |
| Dominant US regions | Northern and interior states | Gulf Coast, California, Hawaii |
Two numbers matter most for mapping. First, the 40°F cold threshold explains why roof rats stop where they do; sustained cold collapses their populations. Second, the 100-to-150-foot home range explains why rats never appear "far from anywhere": if you see one, the colony is close.
Norway Rat Range: Temperate Cities and Ports
Norway rats are the rat of the world's temperate zone. Their range covers virtually all of Europe, most of Canada and the United States, temperate Asia, and port cities throughout the Southern Hemisphere.
The limiting factor is water and cold, not food. Norway rats need daily water access and thrive near sewers, rivers, and docks. They tolerate freezing temperatures by burrowing below the frost line and nesting in heated buildings. This is why they reach latitudes as far north as Edmonton and Oslo, where roof rats cannot survive.
Ports are the relay points. A Norway rat population can establish at any dock with grain handling and fresh water, which is why the species appears in isolated sub-Antarctic harbors and on remote islands with supply stations. The rats are not spreading into the wilderness; they are spreading into the human footprint at the edge of it.
Roof Rat Range: Warm Coasts and Tropical Cities
Roof rats occupy the warm band of the planet and climb into whatever shelter is available above ground.
Their range covers the Mediterranean basin, sub-Saharan coastal Africa, the Indian subcontinent, Southeast Asia, coastal Australia, and the southern United States from Texas to Florida. They are also established in Hawaii and much of Latin America. In these regions they often replace Norway rats entirely in above-ground habitats, while both species coexist in sewers and ground cover.
The cold boundary is sharp. Roof rat populations in the southern US contract after hard freezes and expand again in mild winters. This makes their map more variable year to year than the Norway rat map, which is why pest agencies in border states like Tennessee and Virginia track roof rat reports as a climate signal.
A Timeline of When Rats Arrive After Conditions Change
Rats respond to new food and shelter on a predictable schedule. The table below shows typical arrival and establishment times once conditions change. Times assume an existing population within about half a mile.
| Time after change | What happens |
|---|---|
| 0–3 days | Rats detect new food source; scouting activity begins |
| 1–2 weeks | Burrows or nests established near the source |
| 3–4 weeks | First litter born in the new location |
| 6–8 weeks | Visible population; droppings and runs appear |
| 2–3 months | Colony fully established with overlapping generations |
| 3–6 months | Range expands to adjacent structures |
| 6–12 months | Population plateaus at carrying capacity of the site |
| Removal of food and shelter | Decline within 2–4 weeks; local extinction in 1–3 months |
The key number is the 3-to-4-week breeding lag. A food source that appears and disappears within two weeks rarely produces a lasting colony. A source that persists for a month reliably does.
What a Rat Map Gets Wrong: Three Misconceptions
The most common misunderstanding is the "one rat means an infestation" rule. A single rat sighting usually means a small, local colony, not a neighborhood-wide problem. Norway rat home ranges are only 100 to 150 feet, so a rat in your garage is likely living within a few houses of it, not migrating across town.
The second misconception is that rats avoid wealthy areas. Rat density tracks food waste and old infrastructure more than income. Historic districts with aging sewers and dense restaurant rows often carry higher Norway rat densities than newer suburbs, regardless of property values.
The third is the belief that rat maps are static. Roof rat range in particular shifts with winter severity, and Norway rat range shifts with port trade and sewer condition. A map drawn in 2020 will not match 2026 in border regions.
What to Actually Do If Rats Are on Your Map
The practical response depends on which species is present and where it is living. These actions address the mechanism, not just the symptom.
- Identify the species before treating. Norway rats need ground-level sealing and sewer control; roof rats need attic and roof-line exclusion.
- Eliminate water before food. Norway rats cannot survive long without daily water, so fixing leaks and covering drains removes habitat faster than removing garbage.
- Seal entry points at 0.5 inch or larger. Both species can pass through gaps wider than a quarter, and young rats through half-inch gaps.
- Remove clutter within 150 feet of the building. This is the Norway rat home range, and clutter within it is nesting habitat.
- Coordinate with neighbors. A colony crosses property lines freely, so single-building control fails when adjacent lots remain untreated.
- Document sightings with date and location. Species and timing data are what turn a local sighting into a usable range record.
Limits of Rat Maps and What They Cannot Tell You
No rat map is a census. Rat populations are estimated, not counted, and estimates carry wide error bars. A city reported as having "one rat per person" is usually extrapolating from trap catches and complaint data, not surveying every block.
Ranges also blur at the edges. In transition zones where Norway and roof rats overlap, species identification from a distance is unreliable, and many reported "range expansions" are actually misidentifications. Climate-driven range shifts are real but slow, measurable in decades rather than seasons.
Finally, maps describe where rats can live, not where they do live at any given moment. Local food supply, building condition, and control effort can empty a mapped habitat for years and refill it within months of neglect. Treat any rat map, including this one, as a probability surface rather than a fixed boundary.