- Mice travel over their entire territory
daily, investigating each change or new object that may be placed there.
- Mice have poor vision, hence their activity patterns rely heavily on
smell, taste, touch, and hearing.
- Mice use the long sensitive whiskers near the nose and hairs on the body
as tactile sensors. The whiskers and hairs enable the mouse to travel in the
dark, adjacent to walls in burrows.
- Mice also have an excellent sense of balance, enabling them to walk along
telephone wires, ropes and similar thin objects.
- Mice are excellent jumpers, capable of leaping at least 12 inches
- Mice can jump against a flat vertical surface using it as a spring board
to gain additional height.
- They can run up almost any vertical surface; wood, brick, weathered sheet
metal, cables, etc.
- They can easily travel for some distance hanging upside down.
- Although they are good swimmers, mice tend to take to water only if left
with no other alternative.
- Mice are basically nocturnal in nature.
- House mice breed throughout the year and can become pregnant within 48
hours of producing a litter.
- There are usually about 6 mice to a litter and females may produce as
many as ten litters (about 50 young) per year.
- It takes 18 to 21 days for gestation, and 35 days for a mouse to mature.
Most mice live anywhere from 15 to 18 months.
- They make their nests out of the same types of soft materials as rats,
and as many as 3 females may use the same nest.
- They commonly nest in insulation in attics, also in stoves and under
- Mice do not
travel far from their nest, about 12 to 20 feet.
The three "R's" of Rodent
Reason - Route - Remove
1. Get rid of the
rodents are being attracted. FOOD. The most common rodent
attractant in urban locations is wild bird seed. Once a constant food
source has been detected, rodents will leave pheromone trails for their
family members to follow. This could result in a large populations
being attracted to your home or business. An abundant supply of food
will also speed up their reproductive cycle. Most people who feed wild birds
don't realize they are probably feeding more rodents than birds. Pet food,
grass seed and poorly stored human food are other attractants.
2. Eliminate the
rodents are taking to
enter living and working space. Once inside a building, rodents will follow
plumbing and wiring to access all levels and many rooms. Gaps around
pipes should be blocked. Pay special attention to pipes under the kitchen
sink, bathrooms, laundry room and hot water tank.
the Rodents. Once you have stopped attracting them and blocked off
their entry points, you can focus attention on eliminating the rodent
population. You will have a hard time attracting rodents to bait on a trap
or poison bait, if you have not eliminated their usual source of food.
Don't bother trying to catch them in live traps. Click
here for the reason.
- Mice normally feed 15 to 20 times per day and will eat pretty much
anything a human will eat.
- Food preference is cereal or seed, but also gnaw through insulation or
wires, sheet rock, storage boxes, etc.
- Mice are nibblers. They do small amounts of damage to many food items in
"home range", rather than doing extensive damage to any one item.
- While mice are nibblers and feed many times in many places, they have two
main feeding periods, at dusk and just before dawn.
- They have to consume about 10% to 15% of their body weight every 24 hours
and require extremely small amounts of water.
Disease & Sanitation Factors
- Mice droppings sometimes are confused with droppings from the larger
species of roaches, such as the American roach.
- Mice droppings are smooth with pointed ends, and are 1/8th to 1/4 inch
- In six months, one pair of mice can eat about 4 pounds of food and during
that period produce some 18,000 fecal droppings.
- Deer mice are a primary vector of
Hantaviral infections which cause
- Mice may infect food with their droppings transmitting such organisms as
salmonella and the microscopic eggs of tapeworms.
- Mice transmit disease in a number of ways including biting, infecting
human food with their droppings or urine, indirectly via the dog or cat and
The most common
way mice transmit disease organisms is by contaminating food with their
droppings and/or urine.
The most threatening organism spread by mice is Salmonella, a cause of food
poisoning, spread via droppings. Other transmittable organisms include
tapeworms via droppings, rat-bite fever via bites, infectious jaundice/leptospirosis/Weil’s
Disease via urine in food or water, a fungus disease (Favus) of the scalp
either by direct contact or indirectly via cats, plague and murine typhus
via fleas, Rickettsial pox via the mite Liponyssoides sanguineus (Hirst),
lymphocytic choriomeningitis via droppings, and possibly poliomyelitis
(polio). Another problem is house mouse mite dermatitis which is caused by
these mites when they feed on humans.
Prevention & Control
Good sanitation is essential for effective long term control. Mice can
enter any opening larger than 1/4 inch, making it virtually impossible to
completely mouse proof a building.
The control of mice can be widely varied, depending on the individual
situation. It may range from physically altering the conditions allowing the
infestation, such as covering holes, filling cracks, etc. to baiting or
Disease in North America that rodents may harbor or disseminate
(Purdue University Cooperative Extension).
and rats transmit diseases to poultry, hogs and other animals. They consume
and contaminate feed, and their constant gnawing causes extensive structural
damage to buildings, including fires. All resulting in financial losses to
To compound the problem, rats and mice breed at an alarming rate. Livestock
and other farm facilities provide ideal conditions for rodents to breed with
abundant supplies of food, water and harborage. A small population of
rodents, left unchecked, could explode to thousands in just a few months.
inspection serves three useful functions:
1. Identifies the rodent species involved.
most common rodent pests in livestock operations are the house mouse, Norway
rat and roof rat. The house mouse is easy to recognize, generally 5-7 inches
in length and gray in color. The common Norway rat, a large rodent usually
13-18 inches in length, weighs 12-16 ounces with reddish brown fur. The roof
rat, found primarily along the west coast and in the southeastern United
States, is a smaller black rat weighing between 6-9 ounces.
mice have unique behavioral characteristics. By identifying the species you
can select rodent control products and strategies appropriate to that
Determines the severity and location of the problem.
the inspection, note where you've seen signs of rodents, which include
burrows, droppings (rat droppings are about 1/2 to 3/4 inch in length;
mouse droppings are 1/4 inch), gnaw marks, and rodent pathways. This
information helps you determine the size of the infestation and where
rodents are living and feeding. In that way, you have a better idea of
how much bait to use and where to place it for optimum results.
Rats and mice are nocturnal and are most active from dusk to dawn.
Seeing them in the daylight usually indicates a heavy infestation.
3. Identifies where sanitation and rodent proofing are needed.
the rodents' sources of food, water and harborage indoors and out, and
wherever possible, get rid of them. Also note areas or entry points where
rodents are getting into buildings, and, wherever feasible, fix or eliminate
these entry points to "build rodents out."
a diagram of your facility that indicates problem areas is useful for
keeping track of your baiting efforts. It'll help you evaluate what is
working or where adjustments are needed in your rodent control efforts.
Steps to setting up a baiting program inside barns, and animal living spaces :
Rodent Bait Stations every 30-50 feet along the inside walls of
all buildings. If necessary, stake or anchor the bait station to the ground
or a permanent surface to prevent it from being moved and to keep the bait
away from other animals.
Place bait blocks in bait stations.
mouse problems, you could also place Mouse Bait Stations every 10-20
feet around the inside perimeter of buildings or wherever you've seen signs
of mice. Be sure that these bait stations fit flush along walls
or in corners with the point directly into the corner. They can also also be
placed along walls adjacent to entry ways to intercept rodents as they
single-feeding type bait in each Bait Station.
Inspect stations frequently until you have activity under
control. Increase baiting in areas that have high rodent activity.
need to adjust the placement of the bait stations depending on the level of
rodent activity. More frequent inspections and baiting may be required in
some areas in the fall when rodents head into buildings for the cold season.
Keep up a
fresh supply of bait.
Rodents will reject rancid or spoiled bait. Bait securing rods also help
bait blocks stay fresh longer by elevating them above the floor of the bait
station, away from any moisture build-up.
Often the best way to control Norway rats is to bait their burrows. Place
loose pellets deep in the burrow or crevice where you've noticed rodent
activity. Try not to disturb the burrows.
burrows in 7 to 10 days after baiting. To monitor activity, close the burrow
with wadded-up paper or cover with soil. Return the following day. A
re-opened burrow means rodents still exist. Continue baiting. Check burrows
periodically as part of your monthly maintenance program.
Grassy and Weedy Areas.
The inspection may reveal rodent pathways leading to buildings. If you
haven't already set up an outside perimeter baiting program, do so to
intercept rodents as they move from their burrows or neighboring fields into
buildings. Again, try not to disturb the rodents' habitat during baiting or
they will migrate to other areas. Once you've gotten the population under
control, trim back weeds and grass to get rid of rodent harborage.
Having trouble with
with no dead or captured rodents to show for your trouble?
The following tips may help solve the problem.
Make sure that rodents are the culprits taking
the bait from your trap. Many times the thief is actually
not a rodent; cockroaches, crickets and even ants could be making off
with your bait. Try dusting the area around the trap with a
non-repellent material such as flour; this will reveal footprints to
identify the pest. Also, glue boards located next to your traps will
capture insects and mice.
Are you using the correct trap?
rat trap does not often capture a mouse, and a mouse trap will only
irritate an adult rat! Make sure that your trap matches your rodent.
Expanded trigger snap traps catch more mice
than a conventional metal trigger trap. The expanded trigger
snap traps are effective simply because the larger trigger provides a
bigger surface for the rodent to step on. An expanded trigger also
provides more leverage, which means it takes less pressure to spring
the trap. Some traps even allow you to set the pressure of the
trigger from soft to firm.
The ultimate bait is one that is accepted by
the rodents and not easily removed from the trigger.
variety of baits to find what works best in your situation. In sites
where food is abundant but nesting material is scarce, soft string,
cotton balls, or strips of cloth are attractive to female mice and
rats. To enhance the material, try applying one or two drops of
vanilla extract as an added lure.
Tie the bait down to the trap or use a sticky
bait, like peanut butter, that cannot be carried away. When
using a sticky bait, smear a small amount on the top and bottom of the
expanded trigger. Some solid baits, like cheese, marshmallows or
chocolate, can be melted onto the trigger with a match. Use a piece
of thread or dental floss to tie down solid baits.
Inspect your trap.
Whether or not a
mouse or rat gets caught depends on the sensitivity of the trigger,
the size of the trigger and the speed at which the kill bar flips
over. If a trap is old and slow, it can be improved by simply
applying a small amount of vegetable oil or bacon grease to the
spring. Do not use machine oil, as this would repel rodents.
Although dirty traps that smell "mousy" catch more mice, do
not let your traps get so gummy that the action of the trigger or the
bar is slowed down. Do not attempt to clean a filthy trap with soap
and water. Not only will the soap repel rats and mice, the water will
warp the soft pine base of the trap, making it unstable and
ineffective. Once a trap becomes too gummy to use, toss it and
replace with a new trap. Snap traps are not very expensive and your
time is important!
Health Threats to School Children from Rats and Mice
Jerome Goddard, Ph.D.
Medical Importance. Rats and mice which live in or near human
dwellings are called Commensal rodents. There are three species of
Commensal rodents in the U.S.- the Norway rat, the roof rat, and the
house mouse. Many other species of "wild" rodents live outdoors -
but still may occasionally be encountered by people.
Commensal - or domestic - rodents are of tremendous public health
importance. They may eat or contaminate human food, carry
ectoparasites such as mites and fleas into close human contact,
cause allergies in sensitive individuals, and be disease carriers.
In addition, there can be direct effects (not indirect such as
disease transmission) of rodents on health such as biting. A study
found an average of 500 cases of human rat bite per year in New York
City between 1947 and 1953.1 In addition, one public health official
estimated that more than 45,000 persons are bitten by rats
nationwide each year.1 Rat bites may become infected with a wide
variety of bacterial organisms, and there is a medical condition
called "rat bite fever".
As to their uncleanliness, rats and mice gnaw through stored food
packaging, eating portions of the product, but - perhaps more
significantly - contaminating it with their feces, urine, and shed
hairs. They also (mostly at night) contaminate food preparation
surfaces such as table tops, food production machinery, and cookware
in cafeterias. Cafeteria workers returning to work in the morning
may think the counter tops are clean, when, in fact, they are
covered with tiny drops of urine and hairs. Also, when rats or mice
heavily infest a building, the place may become infested with
human-biting mites and fleas (from the rodents), as well as taking
on a generalized foul odor from the urine. Large areas inside
buildings become drenched with urine over time, creating a
disagreeable "mousey odor".2
Two notorious human diseases are associated with rats and their
fleas - plague and murine typhus. Both diseases occur in rats and
get transmitted from rat to rat and from rat to people by fleas.
Murine typhus -- a spotted fever like infection -- is one of the
most widely distributed arthropod-borne diseases, occurring in ports
and coastal areas worldwide. Currently, in the U.S., it is
restricted to southern Texas and parts of southern California.3
Plague - the disease that killed one-fourth of the population of
Europe during the 14th century - still occurs in many parts of the
world, with hundreds of cases reported annually. The disease -
especially when it gets in the lungs - may be severe and often
fatal. In the U.S., sporadic cases occur mostly in Arizona,
California, Colorado, and New Mexico.3 Another human disease,
leptospirosis, can also be acquired by contact with rats, their
urine, or soil, food, or water containing the causative organism.4
Leptospirosis may cause high fever, rash, severe headache, abdominal
pain, and sloughing of the skin.
Wild mice transmit another serious disease. Hantavirus pulmonary
syndrome is a rodent-borne virus that can cause severe respiratory
problems and even death. Hantavirus is spread through the urine,
saliva and feces of rodents, especially the deer mouse. Humans
contract the disease by breathing dried particles of their urine or
feces. This can occur by cleaning an indoor area that was infested
by deer mice. The disease causes a victim's lungs to fill with
liquid. Symptoms include muscle aches, fever and possibly chills,
headaches, nausea, diarrhea, abdominal pain and coughing. The
symptoms develop within one to six weeks after exposure. Hantavirus
cases are known to occur mainly in the Southwestern United States
and eastward to Pennsylvania.
In addition to disease transmission, introduction of
ectoparasites, and food contamination, scientists are now finding
out that rats and mice can produce asthma and allergies in the same
way cockroaches and dust mites do. There will certainly be more
research and new findings in this area in the near future.
Apparently, people with allergies can develop hypersensitivity to
proteins in rodent urine, causing asthma attacks. Results of skin
tests on asthmatic children in major U.S. cities have shown that up
to 18% of them have sensitivity to mice and 20% to rats.2,5 In one
study, 95% of inner city homes had detectable mouse allergen
inside.5 This study obviously points out the need for better rodent
control in human dwellings.
Biology of the Pest Species Involved. The house mouse is a small
rodent, weighing only ˝ to 1 ounce as an adult. Mice are usually
dark gray color on the back and light gray on the belly. They may
live their entire lives inside buildings, where they eat almost
anything. However, they seem to prefer grains, meats, peanut butter,
and sweet liquids. The Norway rat, also called the brown rat, wharf
rat, or sewer rat, is the most widely distributed rat in the U.S.,
being found in all 50 states. It is a thick and stocky animal,
weighing about 12 to 16 ounces, and with coarse brown fur and a
blunt nose. The tail is shorter than the head and body length
combined. In contrast, the roof rat (also called the black rat or
ship rat) weighs only about 5 to 9 ounces, has a long tail, pointed
nose, and blackish fur. Both rat species will eat cereal grains,
meats, fish, livestock or pet food, and vegetables. In general,
Norway rats nest in burrows in the ground, behind equipment, in wall
voids, and the like, whereas roof rats nest in trees, vines, attics,
ceiling voids, etc.
Control Options and Health Effects from Non-use of Pesticides.
Control of rats and mice involves sanitation to remove food, water,
and harborage areas for the pests, exclusion of rodents from
buildings (plugging all entry points in a building), mechanical
trapping/removal, and baiting with pesticides (rodenticides). Note:
rodenticides are placed in tamper-resistant containers to prevent
human exposure to the product.
If traditional pesticides (rodenticide baits, in this case) are
not available to pest control personnel for the removal of commensal
rodents in/around schools, then successful elimination of the pests
-- and their associated health risks -- will be extremely difficult,
if not impossible. Pesticides should be considered as important
"public health tools" in the removal of rodents. Failure to have
such tools available to pest control personnel servicing schools
will ultimately lead to children being exposed to rats and mice,
their bites, and the diseases they carry.
In addition, there may be
possible liability on the school's part for not having provided a
safe, pest-free environment.
Weber WJ: Diseases Transmitted by Rats and Mice. Fresno, California:
Thomson Publications, 1982.
Corrigan B: Mice just as important as roaches in allergy studies.
Pest Control Technology Magazine (online), GIE Media, Cleveland,
Ohio, February 7, 2001.
Goddard J: Physician's Guide to Arthropods of Medical Importance.
3rd ed. Boca Raton, FL: CRC Press, 2000.
Benenson AS, ed: Control of Communicable Diseases Manual. 16th ed.
Washington, DC: American Public Health Association, 1995.
Phipatanakul w, Eggleston PA, Wright EC, Wood RA: Mouse allergen. I.
The prevalence of mouse allergen in inner city homes. J Allergy Clin
Immunol 2000; 106: 1070-1074.
ABOUT THE AUTHOR:
Jerome Goddard holds a Ph.D. in medical entomology from Mississippi
State University. He is a public health entomologist and a Clinical
Assistant Professor of Preventive Medicine at the University of
Mississippi Medical Center in Jackson, Mississippi. Dr. Goddard has
written a medical entomology textbook, "Physician's Guide to
Arthropods of Medical Importance" which is now in its Third Edition
and is used by physicians worldwide. In addition, Dr. Goddard has
written two other books on medically important pests, three book
chapters, and 80 scientific articles. He has been a visiting
professor in the Department of Dermatology at the Mayo Clinic, as
well as a member of a National Institute of Health panel convened to
study the future of tick taxonomy in the U.S. In 1999, he testified
before a congressional committee on the public health benefits of
Spread by House Mouse
The common house mouse has spread a new disease. Currently still
considered rare, Lymphocylic choriomeningitis (LCM). Infection
occurs when a human encounters the rodent’s urine, droppings,
saliva, or nesting material. Little or no symptoms result in those
with normal immune systems. Those with weaker immune systems (i.e.
the very old, the very young, etc), will initially have flu-like
symptoms. It can then progress to the symptoms of meningitis or
encephalitis. Most people do fully recover. Studies have shown that
about 5% of urban populations are infected. Other rodents, such as
hampsters and guinea pigs can become infected if exposed to the
virus in pet stores or homes. It is not known to transfer from human
to human contact. Take precautions, and follow the Center for
Disease Control’s advice: If you have mice in your home, do not
touch or stirrup the droppings. Wearing rubber gloves, wet them and
the contaminated area with a disinfectant solution solution. Spray
dead rodents with disinfectant and double-bag rodents, nest
material, and cleaning materials for disposal. Wash hands thoroughly
after handling pet rodents and call a professional to assist in the
control of mice.
Navigational Instinct: A Reason Not to Live Trap Deer Mice in Residences
the rodent that most often invades homes in North America is the house mouse,
Mus musculus, the deer mouse, Peromyscus maniculatus, principal
vertebrate host of Sin Nombre virus (SNV) (1),
also invades homes (2), particularly in
rural areas. Barring deer mice from human habitations would prevent domiciliary
acquisition of SNV. Current recommendations (3)
are to prevent wild rodents from entering homes or to snap trap (kill) them
should they enter.
To conduct longitudinal studies of hantaviruses in southeastern
Colorado on a former cattle ranch now returning to its natural condition as
short-grass prairie, we often stay in an old bunkhouse, used by many research
groups at irregular intervals. The house, furnished with beds and full kitchen
facilities, is well maintained but has openings through which mice can pass to
and from the outside. For safety and cleanliness, we removed mice we found
inside the house, but between April 1996 and April 1998, we live trapped and
released them rather than snap trapping them. Before release the rodents were
identified to species; were measured and assessed regarding general appearance
and health, sexual preparedness, and presence of wounds; were bled for antibody
tests; and were ear-tagged. Nineteen deer mice and one pinyon mouse (a P.
truei, which did not return) were examined and tagged. At first, we simply
released these animals approximately 50 m from the house, but when we realized
that they were returning, we released them at increasing distances (50 m to
1,500 m) from the house; the distances were measured by pace counts by at least
Three deer mice had been captured multiple times in our test grid
(as far as 250 m from the house) before they were first captured in the house.
Once captured in the house, however, they were not captured in traps of the grid
(i.e., outside the house). The mean distance traversed by the five deer mice
that returned to the house was at least 394 m;
mouse returned after being released 500 m and 1,000 m, then 750 m, and 1,200 m
from the house at consecutive daily trapping sessions of 3 days.
Sometime within the subsequent 6 weeks, this mouse returned to the house from
the 1,000-m release point and then from 750 m and 1,200 m away on consecutive
days within our 3-day trapping period. Each of the mice returning to the
house did so within 24 hours of release, two as few as 6 hours after release
from 500 m and 750 m away. Nine mice were captured once; six of eight mice
captured twice were captured at least once more; one was captured 10 times, one
7 times, one 6 times, one 4 times, and two 3 times. Equal numbers of male and
female, adult and juvenile mice were captured in the house, but only adult mice
(5 of 5) returned to the house. Returning deer mice maintained or gained weight
between captures and grew in length at approximately the same rate as deer mice
captured in the test grid.
Some rodents have been documented to move similar distances (e.g.,
1,200 m), but they took more than 2 weeks to complete the trek (4).
Homing ability, site fidelity, and navigational proficiency of rodents are well
documented (5,6). Teferi and Millar (7)
studied the homing ability of deer mice in Alberta, Canada;
of deer mice in that study returned to their home sites (a short-grass prairie
mice traveled 650 m to 1,980 m (mean 1,500 m) and had to cross a river
and pass optimal habitat patches to reach their home sites. Deer mice with
previous homing experience were more successful in returning home (100%) than
inexperienced mice (60%) and faster in doing so (8).
Teferi and Millar (7) suggest that these deer mice were able to navigate in a
direct route to their home sites. We released mice in locations where they had
no direct route to the house; they had to follow a winding road, climb over
rocky outcroppings nearly 17 m high, or otherwise surmount obstacles and
dangers, such as predators (7).
None of the mice we captured had immunoglobulin G (IgG) antibody to
SNV. However, infected deer mice released and then returning to a house or
uninfected deer mice released, infected, and then returning to a house would
increase the likelihood of human contact with an SNV-infected mouse. The risk
would be the same for other hantaviruses infecting other peridomestic rodents.
Against current recommendations that rodents in homes be snap trapped, some
homeowners live trap and release them outside their homes. Our data strongly
support snap trapping mice in homes and provide evidence that released wild mice
return and may place the residents at risk.
We thank T. Davis, S.B. Calisher, and E. Kuhn for their assistance in completing
This work was partially funded by contract U50-CCU-813420-01 from the U.S.
Centers for Disease Control and Prevention.
Charles H. Calisher,* William P. Sweeney,† J. Jeffrey Root,* and Barry J. Beaty*
*Colorado State University, Fort Collins, Colorado, USA; and †University of
Texas Medical Branch, Galveston, Texas, USA
1.Childs JE, Ksiazek TG, Spiropoulou CF, Krebs JW, Morzunov S, Maupin GO, et al.
Serologic and genetic identification of
Peromyscus maniculatus as the primary rodent reservoir for a new hantavirus
in the southwestern United States. J Infect Dis 1994;169:1271-80.
2.Glass GE, Johnson JS, Hodenbach GA, DiSalvo LJ, Peters CJ, Childs JE, et al.
Experimental evaluation of rodent exclusion methods to reduce hantavirus
transmission to humans in rural housing. Am J Trop Med Hyg
3.Centers for Disease Control and Prevention.
Hantavirus infectionsouthwestern United States: interim recommendations for risk
reduction. MMWR Morb Mortal Wkly Rep 1993;42(RR-11):1-13.
4.Ostfeld RS, Manson RH. Long-distance homing in meadow voles, (Microtus
pennsylvanicus). Journal of Mammalogy 1996;77:870-3.
5.August PV, Ayvazian SG, Anderson JGT. Magnetic orientation in a small mammal,
Peromyscus leucopus. Journal of Mammalogy 1989;70:1-9.
6.Fluharty SL, Taylor DH, Barrett GW. Sun compass orientation in the meadow
vole, Microtus pennsylvanicus. Journal of Mammalogy 1976;57:1-9.
7.Teferi T, Millar JS. Long distance homing by the deer mouse, Peromyscus
maniculatus. Canadian Field-Naturalist 1993;107:109-11.
8.Robinson WL, Falls JB. A study of homing of meadow mice. American Midland
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