6. Introduction to Rats
• Belong to rodents order of gnawing
mammals (Rodentia)
– With mice compose subfamily Murinae
– True rats form genus Rattus
(78 to 570 species)
• Two domesticated rat species
– Black
– Brown
7. History of Black and Brown
Rats
• Black rat
– May have come from Southern Asia
– Well established in Europe during 1200s
– Reached North America during 1500s
• Brown rat
– Came from Eastern Asia and Northern
China
– Went to Europe and North America in
1500s
– Now well established in United States
8. Common Background of
Rats
• Have spread across the world
– Can adapt to many different habitats, environments, and
foods
– Reproduce rapidly
• Cause tremendous damage
– Destroy eggs, fruits, stored grain, and vegetables
– Attack humans and other animals
– Damage buildings and cause fires
– Carry diseases
• Play important role in research
– Used extensively in drug development
– Act as subjects in disease, aging, behavioral, and other
studies
9. Black Color Group of Rats
• From 7 to 8 inches long (head and body)
– Tail longer than head and body
– Ears about half as long as head
• Weigh 4 to 12 ounces
• Usually black or dark gray with brown or
gray-white underside
• Excellent climbers and jumpers
10. Brown Color Group of Rats
• From 7 to 10 inches long (head and body)
– Tail shorter than head and body
– Overall thicker, more robust than black rats
• Weighs 7 to 17 ounces
• Dark to gray-brown back with lighter brown
or gray underside
• Not climbers, prefer tunnels, burrows,
sewers, and basements
11. Varied Color Group of
Rats
• Albino (white laboratory rat)
• Cream, fawn, or light gray
• Hooded
• Capped
12. Breeding
• Life span 2 to 3 years
• Puberty at 50 to 60 days
• Continuously polyestrous (minor seasonal variation)
• Gestation 21 – 24 days
– Pregnancy determination @ 14d
– Pseudopregnancy may last up to 14d
• Litter size 7 to 11
– Don’t disturb for 3-4 days after delivery
– Young born pink, naked, blind, deaf
– Young have hair by 1 week old
• Wean at ~21 days
13. Characteristics of
Common Rats
• Agile climbers
• Excellent swimmers
• Highly curious
• Clean and odor free
• Seldom prone to biting
• Imposing when upset or angry
• Gregarious
• Primarily nocturnal
14. Anatomy
• Absence of • Olfactory oriented
gallbladder • Harderian gland
• Open rooted behind eyeball
incisors secrets porphyrin
• Extensive mammary • Average weight
tissue 350g
• Have an os penis • Altricial
15. Desired Qualities of Rat Cages
• Larger than 12” x 24” x 12” ESCAPE PROOF
• Nest box & 2-4x more space if breeding
• 65-80 F temperature, 40-70% humidity
• Wire mesh or glass sides
• Solid bottom or pull-out tray
• Outside-hanging water bottle (spout inside)
• Glass or ceramic feed bowls
• Exercise equipment (ladders, ropes, wheels)
• Wood shavings or other appropriate bedding
– Change 1-2x per week or more if moist/odor
• Nesting materials
16. Methods of Feeding Rats
• Commercial pellets easiest option
• Supplements – NOT NECESSARY
– Dry dog food, crackers, cereal, fruits or
vegetables (less than 5-10% of diet)
– Vitamins and minerals
• Daily water
– One ounce per rat
– Closed dish, sipper bottle
17. Behavior
• Long Evans more aggressive than
albinos
• Communal
• Young are communally raised
• Burrowers
• Nocturnal
18. Methods of Handling Rats
• Young rats
– Grasp around body, just behind front legs
– By tail, grasp at base close to body
• Older rats
– Use talking as relaxation technique
– When not tame: Go slowly, get attention, grasp by
base of tail, and lift
– For further restraint: Place second hand around
body just behind front legs and restrict head
movement with thumb and forefinger
19. Rat Diseases and Ailments
• Neoplasia
• Respiratory disease
– Commonly caused by Mycoplasma pulmonis
– Treatment with antibiotics
– Controlled with good sanitation and ventilation
• External parasites (lice and mites)
– Cause hair loss, itching, more
serious symptoms
– Controlled with shampoo containing pyrethrin
20. Mycoplasmosis
(respiratory disease)
• Signs: Sneezing, nasal discharge, eye
discharge, labored breathing
Treatment: Long term antibiotics
Prevention: Clean environment, good
ventilation
21. Red Tears
(sialodacryoadenitis)
Signs: Because rodents have
porphyrins (pigment) in their tears, any
discharge will be red.
Causes: bacterial infection or stress
Treatment: Topical eye ointment
22. Mammary Neoplasia
Frequently develop tumors. Mammary
tissue covers most of the body, so lumps
can appear anywhere.
Grow quite large , are uncomfortable
and may ulcerate and become infected.
Surgical removal is necessary
27. History of Common
House Mice
• Believed to have originated in Asia
• Gained place in history
– Egyptians and Romans used phrases like “It’s
raining mice” or “Mice are made of raindrops”
– Cretans worshiped mice over 4,000 years ago
– Mice were used as medicines in ancient Rome
and during Middle Ages
– Japanese bred white/colored mice 3,000 years
ago
• Today house mice are widely used in medical
and biological research
28. Basic Color Groups of
Mice
• Self or single colors
• Tans, any recognized colors with tan
belly
• Piebald or pied marked
• Satins of any color or markings but with
satinized coat
• Any other variety
29. Breeding
• Life span 2 – 3 years
• Puberty at 28 to 40 days
• Gestation period 21 days
• Litter size 6 – 12
• Weaned at 21 days
30. Mouse Reproduction
• Sexual maturity
– Females at 4 weeks
– Males at 5 weeks
• Gestation period normally ~21 days
• Litters range from 5 to 10 to 1 to 20
– Young born helpless, hairless, and blind weighing
~1 to 2 grams and measuring ~1/2” long
– Touch no young for at least a week
– Separate by sex at about 3 weeks to prevent
unwanted matings
31. Characteristics of
House Mice
• About 2½ to 3½” long (without tail)
• Weighs ½ to 1 ounce
• Small head with long, narrow snout
• Gray-brown back, light to white underside
• Large, round, black eyes
• Large ears and well-developed hearing
• Highly developed sense of smell
• Primarily nocturnal
• Gregarious
32. Anatomy
• Porphyrin Glad • Extensive mammary
behind eyeball tissue
• Small size 25-40 • Fecundity – one pair
grams plus one year
• Open rooted equals one million
incisors • Altricial
• Males have larger
spleen than females
33. Desired Qualities of
Mice Cages
• For mouse pair at least 72 square
inches of floor space and 8 inches of
height
• Plastic bottom and closely spaced bars
• Cover or lid
• Wood, nondusty shavings or other
appropriate bedding
• Vacuum-type water bottle
34. Nutrition/Housing
• Metal or plastic cages with wire mesh
• Water bottles
• Bedding & nesting materials
• Commercial diets
• No supplements
35. Common Foods for Mice
• Grains and seeds as main foods
– Commercial pellets
– Grain/seed mixture
• Ration of corn, oats, and wheat with
small amounts of millet, barley, and
buckwheat
– Feed sunflower seeds sparingly
– Give small amounts of oily seeds
– Add greens and vegetables
• Fresh hay as supplement
36. Behavior
• Timid
• Territorial
• Escape prone
• Social order poorly understood
• Males cannot be housed together after
sexual maturity MOB Syndrome
• Will bite when handled roughly
37. Clan/Colony Structure of House
Mice
• Ruled by lead or head buck
– Only lead buck mates, all other males subordinate
– Subordinates challenge buck through aggression
– Defeated buck moves to bottom of social structure
• Females together raise, warm, nurse/feed
young
• Structure provides protection and makes
finding and storing large quantities of food
easier
– Members leave urine marks while searching
– Marks fend off members of other colonies
38. Methods of Handling
Mice
• Two ways to lift
– Grasp by base of tail
– Scoop up in cup
• Allow adjustment period when first
home
• Offer treats from fingertips and then
palm
• When tamed, stroke head and ears
40. Common Diseases
• Mammary Neoplasia – same as rats
• Mycoplasmosis – same as rats
• Viral Diseases: more a problem is
laboratory colonies than in pet mice
• Antibiotic toxicities: Procaine and
streptomycin are fatal to mice
Editor's Notes
Mice are small rodents used most often in research setting, but are maintained as pets. Life span of 2 years, and are prone to geriatric disease conditions soon after ownership.
