Rats

· Various species are problematic in the U.S., mainly the 
Norway rat and roof rat. 

· Bite more than 45,000 people each year, according to the 
U.S. Centers for Disease Control. 

· Can burrow three feet straight into the ground, chew 
through building materials such as glass, cinderblock,
wire, aluminum and lead, and can climb inside pipes with 
diameters between one-half and four inches. 

· Primarily rely on smell, taste, touch and hearing. 

· Eat and urinate on human and animal food. 

· Support many ectoparasites. 

Mice

· A female house mouse gives birth to a litter of 
approximately six mice about 19 days after mating and is 
capable of mating again in two days. 

· Can produce six to 10 litters a year. 

· Are able to mate two months after birth. 

· Can produce 2,500 heirs in six months, with ideal 
conditions and no mortality. 

· Establish a nesting site near sources of food and 
feed 15 to 20 times a day

1. Gnaw marks. New gnawings or holes tend to be rough 
whereas, old gnawings are smooth from wear.
   

2. Droppings. Fresh droppings are soft and moist whereas, 
old droppings are dried and hard; adult roof's about 1/2" 
(12-13 mm) with pointed ends vs. Norway's about 3/4" 
(18-20 mm) with blunt ends.
  

3. Tracks/footprints. Front foot 4-toed and print is in 
front of usually longer hind print with 5 toes. Fresh 
tracks are clear and sharp
  

4. Rub marks or dark, greasy markings on vertical 
surfaces. Fresh marks are soft, greasy, and easily 
smeared whereas, old marks are with the grease dry 
and flaky. Swing marks often present around rafters.
  

5. Burrows. Not common, but if present they are shallow. 
They usually nest in or under vegetation.
  

6. Runways. Travel routes may not be apparent outside 
because they may travel along fences or on overhead 
power or telephone lines. Indoors, they usually move 
along walls, stacked merchandise, etc. Active runways 
with greasy appearance, free of dust and cobwebs, with 
fresh tracks and/or droppings.
  

7. Damaged goods. Roof rats prefer fruits, vegetables, 
and cereal whereas, Norway rats prefer meat fish and 
cereal. 



BIOLOGY.
 

Roof rats reach sexual maturity in 2-5 months. Pregnancy 
lasts an average of 22 days. The young are blind and 
naked at birth, with hair appearing in about 7 days and 
eyes opening in 12-14 days. They are weaned at about 3-4 
weeks. The average number of litters is 4-6 per year, each 
containing an average of 6-8 young. Adults on an average 
live 9-12 months.

They have rather poor vision and are color blind, but 
their senses of hearing, smell, touch, and taste are 
keenly developed. Touch is via their vibrissae or long 
whiskers. They are good runners, excellent climbers and 
jumpers, and if forced, rather good swimmers.

A roof rat requires 1/2-1 oz (14-28 g) of food and 1 oz 
(30 ml) of water each day, with the water often coming 
from its food. This results in about 30-180 droppings 
and 1/2 oz/3 teaspoons (16 cc) of urine per day.

Historically, bubonic plague has been associated with 
the roof rat and its fleas, which move from infested 
rats to man. Fortunately, plague has not been found in 
rats in the United States for many years. Other 
transmitted disease organisms include murine typhus via 
fleas (also probably via droppings and urine), infectious 
jaundice/leptospirosis/Weil's Disease via urine in water 
or food, rat-bite fever via bites, trichinosis via 
undercooked pork, and food poisoning or Salmonellosis via 
droppings. Another problem is tropical rat mite dermatitis 
which is caused by these mites when they feed on humans.

HABITS. Roof rats are primarily nocturnal in habit and 
they are very cautious. Although they constantly explore 
their surroundings, they shy away from new objects and 
changes. Roof rats prefer to nest in the upper parts of 
structures but may be found under buildings as well as 
occasionally in basements and sewers. Outdoors, they 
prefer to nest in higher places such as in trees but may 
occasionally be found in burrows in or under vegetation 
around the structure. These are social animals but less 
so than Norway rats. Several nests may be located within 
a given area. An opening of greater than 1/2" (12 mm) is 
required for entry into buildings.

Although they will eat practically anything, roof rats 
prefer fruits, vegetables, and cereals. If the eaten food 
material proves disagreeable, they are quick to develop 
food/bait shyness. Once they find an acceptable/preferred 
food, rats tend to eat their fill at one sitting/place 
and will return time after time.

Once established indoors, roof rats tend to follow the 
same route or pathway between their harborage and food 
and/or water sources. Runways along vertical surfaces 
will usually include dark rub or swing marks on the 
vertical surface where their fur makes contact. Their 
runways will be free of debris, and outdoors, the grass 
will be worn away to the bare soil.

CONTROL. The key to any rat control program is pest 
identification, sanitation, harborage elimination, and 
rat-proofing the building. Control is based on the 
behavioral habits of the roof rat. Some of the more 
important things to remember are: 

1. Rats defecate where they spend most of their time. 
Use rat droppings as an indication of where to 
concentrate the control efforts. Nontoxic tracking 
powder can also be used to determine where they are 
most numerous.
   

2. Rats will travel 100-150 ft (30.5-45.7 m) for 
food and/or water along established runways. Look for 
rub/swing marks and clean runways. Place traps or bait 
stations along runways and against vertical surfaces. 
Glue boards wired to traveled pipes, rafters, etc. 
are effective.
  

3. Rats are gluttons. Place sufficient bait in each 
bait station for at least 1 meal (stop-feed baits), 
2 meals (acute/single-feed baits), or more 
(chronic/multi-feed baits). Once a preferred bait is 
found, they utilize this bait until feeding stops.
  

4. Rats are cautious. Minimal disturbance is desirable 
when putting out traps and/or bait stations. 
Pretrapping with unset snap traps or prebaiting with 
nontoxic bait may be necessary.
  

5. Roof rats prefer fruits, vegetables, and cereals. 
Use such high-carbohydrate baits and bait the center 
of glue boards and snap traps with such foodstuffs.
  

6. Rats usually have a water source other than their 
food if their food has a low moisture content. 
Liquid baits are particularly effective when their 
normal water source can be reduced or eliminated.
  

7. Roof rats sometimes nest in ground burrows. 
Outdoors, gassing (fumigating) rat burrows is 
extremely effective. Follow label directions and do 
not gas burrows within 15 ft (4.6 m) of, or burrows 
which may run under or open into an occupied 
structure.