Rodent Cage Capacity Policy

Policy for BUMC: Laboratory Animal Science Center

Minimum Cage Space Requirements (All Species)

The Laboratory Animal Science Center (LASC) is committed to upholding minimum cage space requirements for all laboratory animals. For most laboratory animal species, the cage size is mandated by federal law¹. The “Guide for the Care and Use of Laboratory Animals” reflects these laws and sets additional standards that are utilized by the American Association for Accreditation of Laboratory Animal Care (AAALAC) in their program review procedure².

Recommended Space for Commonly Used Group-Housed Laboratory Rodents

Animals Weight, g Floor Area/Animal, in2 a Heightb, inc
Mice <10 6 5
Up to 15 8 5
Up to 25 12 5
>25d >15 5
Rats <100 17 7
Up to 200 23 7
Up to 300 29 7
Up to 400 40 7
Up to 500 60 7
>500d >70 7
Hamsters <60 10 6
Up to 80 13 6
Up to 100 16 6
>100d >19 6
Guinea pigs <350 60 7
>350d >101 7

a To convert square inches to square centimeters, multiply by 6.45.
b From cage floor to cage top.
c To convert inches to centimeters, multiply by 2.54.
d Larger animals might require more space to meet performance standards.

Recommended Space for Rabbits, Cats, Dogs, Non-Human Primates, and Birds

Animals Weight, kga Floor Area/Animal, ft2 b Height c ind
Rabbits <2 1.5 14
Up to 4 3.0 14
Up to 5.4 4.0 14
>5.4e >5.0 14
Cats <4 3.0 24
>4e >4.0 24
Dogsf <15 8.0 -
Up to 30 12.0 -
>30e >24.0 -
Monkeysg, h
(including baboons)
Group 1 Up to 1 1.6 20
Group 2 Up to 3 3.0 30
Group 3 Up to 10 4.3 30
Group 4 Up to 15 6.0 32
Group 5 Up to 25 8.0 36
Group 6 Up to 30 10.0 46
Group 7 >30e 15.0 46
Apes (pongidae)h
Group 1 Up to 20 10.0 55
Group 2 Up to 35 15.0 60
Group 3 >35 25.0 84
Pigeons - 0.8 -
Quail - 0.25 -
Chickens <0.25 0.25 -
Up to 0.5 0.50 -
Up to 1.5 1.00 -
Up to 3.0 2.00 -
>3.0e >3.00 -

a To convert square inches to square centimeters, multiply by 6.45.
b From cage floor to cage top.
c To convert inches to centimeters, multiply by 2.54.
d Larger animals might require more space to meet performance standards.

“Guide for the Care and Use of Laboratory Animals”, Institute of Laboratory Animal Resources,   Commission on Life Sciences, National Research Council, National Academies Press, Washington, DC. Copyright ©1996 by the National Academy of Sciences. All rights reserved.

Housing and Animal Aggression

Group-housed rodents typically develop dominance hierarchies. Male mice of certain strains (e.g., BALB/c, CD-1) are notorious fighters that will inflict severe wounds on their opponents during repeated battles. In severe cases, mortality may be directly or indirectly caused by fighting. It is highly recommended that newly received animals be housed in caging groups that are expected to be appropriate for the duration of the housing period. The mixing of unacquainted animals as new cage-mates frequently causes significant stress as the animals struggle to establish a new social dominance hierarchy. If experimental variables are to be minimized, animals should not be redistributed into new social groupings during or immediately prior to the experimental period. Creation of a stable social grouping within each cage immediately following shipment will allow the animals to establish their dominance hierarchy during their recovery from the stress of shipment. Even with these precautions, inter-mouse aggression may subsequently develop in previously “stable” groups of male mice.

LASC Policies

Mice 7″ X 11″ Style Shoebox
(Bldg. W/R/M)
8″ X 13″ Style Shoebox
(670 Albany St., x-2)
4 adult males 5 adult males
5 adult females 6 adult females
2 adults & 1 litter 2 adults & 1 litter
Rats 10″ X 19″ Standard Shoebox Caging
1 adult >500g body weight
1 adult female & 1 litter
2 adults,  400–499g body weight (each animal)
3 animals, 300–399g body weight (each animal)
4 animals, 200–299g body weight (each animal)
6 animals, 100–199g body weight (each animal)
8 animals, <100g body weight (each animal)

Authorized Cage Population, Rodent, Per Cage

Newly received animals will be housed according to the table above or according to the investigator’s specification on the animal order form, whichever stipulates the fewer number of animals per cage. The LASC staff may request confirmation of an investigator’s request to house mature male mice of aggressive stocks or strains at >1 per cage.

Rats and mice will be weaned and placed into appropriate housing groups at 21 days of age unless special arrangements are made by the investigator and approved by the IACUC.

The LASC staff will tag overcrowded cages. Investigators will be notified by phone or email the first three occasions when cage space requirements are exceeded. The investigator’s lab personnel will generally be allowed 48 hours to correct non-emergency problems. If animal overcrowding is not corrected within 48 hours of notification, the LASC staff will remedy overcrowding by distributing the animals into an appropriate number of cages. The new cages will be identified and added to the investigator’s cage census form. The investigator’s account will be charged for the LASC technical services provided.

Male mice that have been fighting (as evidenced by bite lesions on the rump and tail) will be separated into successively smaller groups until fighting ceases. Individual (one per cage) housing will be provided for any mouse that has been seriously traumatized by aggressive cage-mates. Euthanasia may be stipulated if a mouse has serious medical problems as a result of fighting. All occupied mouse cages must be appropriately identified. The separation of overly aggressive mice is the responsibility of the first person (either LASC or research staff) who observes the problem. Request help from the LASC staff if you have any questions about the condition of mice.

References (Available from LASC Upon Request)

  1. Animal Welfare Act; United States Department of Agriculture–Animal & Plant Health Inspection Service. 9 CFR.
  2. “Guide for the Care and Use of Laboratory Animals”. National Academies Press. 1996.
  3. Patterns of Behavior. R. E. Wimer and J. L. Fuller. In The Biology of the Laboratory Mouse. E. L. Green, ed. 1966.
  4. Effects of Shipping on the Immune Function in Mice. M. S. Landi, J. W. Kreider, C. M. Lang, and L. P. Bullock. Amer. J. Vet. Res. 43: 1654-1657. 1982.