Rats are some of the most populous mammals on the planet, found in nearly all areas that humans inhabit. Like mice, many rats have a commensal relationship with humans, depending on us for food and shelter. Two species of rats are most prevalent in North America - the Norway rat and the Roof rat - both of which cause significant damage to homes, farms and businesses. Learn about these two species below, including where they live, what they eat and how to control them.
General Rat Facts
|Species||Norway rat; Brown rat||Roof rat; Black rat|
|Scientific Name||Rattus norvegicus||Rattus rattus|
|Average Size||7-10" long with 6-8" tail; 7-18 oz.||6-8"long with 7-10" tail; 5-10 oz.|
|Average Lifespan in the Wild||5-12 months||5-18 months|
|Identifying Features||Thick body with grey or brown fur; small eyes and ears; blunt snout; hairless tail shorter than body.||Slender body with black or brown fur; larger eyes and ears; pointed snout hairless tail longer than body.|
Thanks to their adaptability and propensity to live in conjunction with humans, rats are widespread across the globe. The Norway rat in particular is very populous, inhabiting nearly all corners of the earth except for Arctic and Antarctic regions.
The roof rat is also very populous, found mostly in warmer climates. They're common in Europe, Asia, southern Africa, Australia and in coastal regions of North America
Rats thrive in most environments where food and shelter are available. Norway rats can be found nesting in and around homes, warehouses, office buildings, barns, cellars, sewers, garbage dumps, and other areas that provide ample food. For shelter, they will construct nests at or below ground level.
Roof rats are generally found further from the ground in trees, cliffs, attics, upper levels of warehouses, wall cavities and roofs. Although they will occasionally live at ground level, they prefer to nest in more aerial locations.
Rats are omnivores and will eat almost anything. They are often found feeding on garbage and other human scraps, however each species has its own dietary preferences.
Norway rats prefer a well-rounded diet of fresh foods, such as:
Roof rats have a more vegetarian diet, favoring foods like:
- Activity: Nocturnal in nature, rats generally emerge at dusk to do most of their activity and feeding throughout the night.
- Reproduction: Rats reproduce fairly rapidly, giving birth to 6-12 young, 3-6 times per year. Peak breeding season occurs in spring and fall.
- Social Interaction: While the social behavior of Roof rats is not well documented, that of Norway rats generally depends on the population density. In areas of low density, there is one male per group who is very territorial and acts as the sole mating partner of each of the females. In areas of higher density, male rats tend to be a bit less territorial, with several males per group.
- Burrowing: Norway rats burrow for shelter, warmth, nesting and food storage. Burrows generally begin next to buildings, fence lines or other forms of cover. Roof rats do not commonly burrow, unless trees or other forms of shelter are unavailable.
Identify Rat Damage
Rat damage can resemble mouse damage in many ways, but it's important to understand the difference - especially when controlling an infestation. Generally rat damage tends to be larger than that of a mouse - e.g. larger bite marks, larger droppings, larger grease marks.
Common signs of rats include:
- holes about 2" in diameter in food packaging.
- tooth marks on wooden baseboards, cabinets, windowpanes, doors, etc.
- chewed electrical wire, piping or insulation.
- grease marks on walls, baseboards, cabinets, doors, etc.
- rat droppings: dark pellets with blunted ends, about 3/4" in length and 1/4" in diameter.
- rat tracks: small prints; four toes in front feet and five on longer hind feet; claw marks and/or tail mark often visible.
Rats and Diseases
Rats are vehicles for many diseases to which humans and pets are susceptible, which is one reason why controlling the rodent population in and around your home is so important. Some diseases rats can transmit to humans include:
Diseases transmitted by the common house mouse include:
- bubonic plague
- hemorrhagic fever
- murine typhus
- rat-bite fever
There are many ways humans or pets can contract the above diseases from rats, including rat bites/scratches, ingesting contaminated food or water, inhaling contaminated dust, direct contact with an infected rat, and bites from infected fleas, ticks or mites.
- Rats are the second most successful mammals in the world, behind humans.
- One female Norway rat may give birth to up to 20 young in a year.
- Rats are skilled swimmers and have been known to travel through sewage systems and enter homes through drains and even toilets.
- Similar to cats, rats will scent mark with urine to communicate with each other. This is often done to establish dominance in a territory.
- A single rat can produce up to 25,000 droppings in one year.
- A rat's teeth never stop growing, so rats must always be gnawing to keep them maintained.
- The tooth enamel of rats is said to be stronger than steel.