Old-World or European rats, roof rats (Rattus rattus)
and Norway Rats (Rattus norvegicus), have been
living in association with human populations for
centuries. Once transported into a new geographic
area, they generally breed quickly, since they have
adapted to living in urban areas.
For information on the Rodent Surveillance Program, visit the Zoonotic Diseases webpage.
The Norway rat is larger and more aggressive than
the roof rat. The Norway rat has a short tail, shorter
than the head and body combined, with a blunt nose
and small ears. The Norway rat may weigh 12-16
ounces and grow to a total length of 13-18 inches.
The Norway rat thrives in unsanitary conditions,
and is an opportunistic scavenger. Norway rats are
much more likely to infest structures than are roof
The Roof rat is smaller than the Norway rat,
weighing only 5-10 ounces, with an total length of
10-14 inches. Roof rats have larger ears than Norway
rats, and tails longer than their bodies. Roof rats
prefer “natural” foods such as seeds, nuts, fruits and
vegetables, but will scavenge if necessary.
Both species are nocturnal, foraging at night, and
usually stay in or close to burrows during the
daytime. Both species are rarely seen during the day, unless the competition for food and habitat is
significant. Both require heavy vegetation for
burrowing and a reliable source of water.
These species can reproduce quickly, becoming
sexually mature in 2-3 months, and are capable 4-6
litters per year, with 4-8 pups per litter. This allows
infestations to expand rapidly if they have an
In the Las Vegas Valley, Norway rat activity has
been rare. Roof rats have been documented in the
Las Vegas valley since 1990. Initial identifications were made in the south/central part of the valley,
and associated with imported palm trees. Reports of
roof rats are often associated with areas near washes
and/or areas with heavy vegetation and standing
Uncontrolled rodent populations can cause
significant adverse affects in the community.
rats can produce large quantities of fecal pellets,
urine, and hair, which are capable of soiling and
contaminating large areas.
Nesting, burrowing and
gnawing can cause direct property damage.
rats and their associated parasites can transmit
plague, typhus, salmonella, leptospirosis, rat bite
fever, and other diseases.
Rodent Control Measures
Weatherproof your home’s windows and doors
(eliminate light from around doors).
openings, pipe chases and wire entrance gaps
with steel wool, aluminum, or wire mesh.
pet doors at night.
Eliminate any unnecessary clutter, material,
brush or foliage from your property.
bushes trimmed and clean out leaf litter and
clutter that collects below bushes.
landscaping debris quickly.
Stack firewood 12
inches off the ground and keep the area clean.
Keep trash cans (plastic or metal) covered.
not put out “food” garbage in plastic bags.
sealed plastic bags in trash cans.
Do not leave pet
food outside overnight.
It is recommended that rodent control be
conducted by a commercial pest control
company that is licensed by the Nevada
Department of Agriculture.
glue and snap-type traps are effective
in reducing rodent numbers.
Do not place traps
where they may be accessible to children or pets.
Over-the-counter poison baits can also be useful,
provided the label directions are followed, but
should not be used in households with children
or pets, unless under the direction of a licensed
pest control company.
Download the Rodents ChecklistPDF (222 KB/5 pages) to learn more on how to inspect for rodents on your
For more information on rodent pests and control
measures, visit the links from our Related Websites page. Information on the Rodent Surveillance Program is available on the Zoonotic Diseases webpage.