General Rodent Information

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General Background on Rodents:

Rodents are found worldwide except in Antarctica and on some small islands.  Some spend their entire lives above the ground in the canopy of rainforests; others rarely emerge from beneath the ground.  Some rodents are highly aquatic, while others are equally specialized for life in deserts.  Many rodents are omnivorous; others are highly specialized, eating, for example, only a few species of invertebrates or fungi. Coprophagy, or eating of feces, is well-known in rabbits, but rodents also do it. 
 
The common pet rodents are rats, mice, hamsters, gerbils, guinea pigs and chinchillas.  Rats, mice, hamsters, and gerbils belong to the Family Muridae in the rodent suborder Sciurognathi, one of the two major suborders of rodents.  Chinchillas are placed in the other rodent suborder Hystricognathi. 
 
All rodents share one characteristic: a highly specialized dentition for gnawing (the term rodent is derived from the Latin rodens meaning gnawing).  Rodents have a single pair of upper and a single pair of lower incisors.  Between each incisor and the first cheek tooth is a toothless interval called the diastema.  The incisors are rootless and grow continuously.  Rodents deposit enamel on the anterior and lateral incisor surfaces; the posterior incisor surface is dentin.  During gnawing, as the incisors chisel against each other, they wear away the softer dentin, leaving a sharp enamel edge.  This "self-sharpening" system is very effective and is one of the keys to the enormous ecological success of rodents.
 
Housing:
 
 The immediate physical environment of the cage or enclosure surrounding a rodent can be quite different from the environment in the surrounding room.  Temperature, humidity, and concentrations of gases and particulate matter are often higher in an animal's cage.  These micro-environmental conditions can alter metabolic and physiologic processes that predispose the rodent to diseases. The microenvironment is considered the cage itself, feeders and water bottles, equipment for environmental enrichment, and cage complexities such as platforms, and multiple levels. 
 
With rats and mice, we can state with confidence that their housing should include nesting materials and boxes, tunnels and running-wheels. Aquariums are not suitable cages for rats and mice because of inadequate air circulation.  The best cages are made of a material that will be easy to clean and deodorize and is indestructible to rodent chewing or digging in the corners.  The cage floor can be solid, but should be waterproof and easy to clean.  We do not recommend wire mesh floors because rats and mice can trap their feet and especially hind limbs in the openings, resulting in fractures and injuries. Any cage should provide a secure environment that does not allow escape.  It should be free of sharp edges or projections that could cause injury and not allow accidental entrapment of animals or their limbs in structural or floor openings.
 
Owners should house different species of rodents separately to prevent interspecies disease transmission. Housing male and female rodents together will result in mating and subsequent litters. Female mice become sexually mature at 6 to 8 weeks of age and female rats are sexually mature by 10 weeks of age.  Unless opposite sex rodents housed together are separated or neutered, having a new litter every 3-5 weeks is possible.
 
Bedding: 

The purpose of bedding is to keep animals dry and clean. Bedding can be described wood-based (chips, shavings, peelings, wood-wool and sawdust); paper-based (cotton and pulp fiber, recycled paper), corn (husks and cobs); cellulose and vermiculite. Some pet bedding contains lemon and chlorophyll to give them a pleasant scent; this type of bedding irritates pet rodents, and the coloring agents can stain white rats or mice, so we do not recommend this bedding. Change bedding regularly to reduce odor and toxic ammonia from building up. We discourage the use of wood products due to the build up of aromatic fumes that can be harmful.
 
Treats and Diet/Nutrition:

            Do not underestimate the value of food treats.  These can range from simple inexpensive treats such as a daily piece of a breakfast cereal such as Cheerios (General Mills, Minneapolis, MN) to formulated nutritious or calorie-free treats. We caution owners not to offer treats by placing them between the wire openings of the cage.  Rats conditioned to accept treats this way, can mistakenly bite fingers that are innocently placed between the wire openings when strangers or guests visit, or when the cage is held or moved.
 
Feeding: 

            Fresh food and water should be available at all times. Fresh water should be available 24 hours a day and is usually provided in sipper tubes available at pet stores, although it can be placed in spill-proof crocks. The water should be replaced DAILY and the tubes (specifically the end the pet drinks from) inspected daily for blockage that can develop if the pets spits food into the sipper tube.
 
Feeding Rats and Mice:

Rats and mice are not strict herbivores like rabbits, guinea pigs, or chinchillas.  They are omnivores and will eat food of both plant and animal origin.  In the wild rats and mice will eat a wide variety of seeds, grains and other plant material as well as invertebrates, small vertebrates and carrion.  Their ability to scavenge partly accounts for their successful colonization of diverse geographic regions. Specially formulated diets for laboratory rodents that come as pellets are convenient and nutritionally balanced sources of nourishment. Obesity in pet rats and mice is common, calorie restricted pets live longer.  Consequently, the amount of pelleted diet owners provide daily should be limited.  Owners should supplement their pet’s diet with feeds high in fiber such as vegetables, limited amounts of fruit, and occasional treats. 
 
Illness: 

Recognizing disease in prey species such as rodents is more difficult than recognizing disease in predators like dogs, cats, or ferrets.  Prey species are very good at hiding signs of disease and pain as a survival mechanism.  Any obvious indication of weakness makes that animal an easier target for a predator.  Self-induced analgesia is part of a rodent's defensive behavior system. Anorexia, or decreased appetite, is a general indicator of an underlying problem.  If anorexia is suspected, place the pet in a separate smaller enclosure so you can evaluate it more carefully. Lethargy or weakness is unusual in rodents.  Many things such as dehydration, anorexia, heat prostration, and infection can result in lethargy/weakness.  A veterinarian should promptly evaluate any rodent that is lethargic or weak. 
 
Normal rodent droppings can vary in color from black to tan, and in consistency from hard pellets to firm paste.  Changes in the droppings can indicate an underlying problem.  If the droppings are dry, it might be due to dehydration.  Smaller than usual droppings generally means the pet has decreased its food intake.  When diarrhea is present, a stool sample should be evaluated for abnormal gut flora, microbial or parasitic infection. 
 
WHEN TO CALL: 

The owner is the best person to perceive a change in their pet's normal behavior.  Abnormal behavior may consist of any or all of the following:  lethargy, weakness, personality change, dietary habit change, sneezing, head tilt, ocular discharge, nasal discharge, or chattering. 
 
 
Table listing average life spans of different pet rodents
 
Mice
Rats
Hamsters
Gerbils
Degus (Chinchillas)
1.5 years
2 years
1.5 years
3 years
7 years
 
Reproductive characteristics of pet rodents
 
 
Rat
Mouse
Sexual maturity in weeks (male)
6-10
6-8
Sexual maturity in weeks (female)
8-12
6-8
Breeding life in months (male)
9-12
9
Breeding life in months (female)
9-12
9
Estrous cycle length (days)
4-5
4-5
Estrus duration (hr)
10-20
10-20
Ovulation rate (egg number)
10-20
6-10
Gestation (days)
21-23
19-21
Pseudopregnancy (days)
12
12
Litter size
8-18
5-12
 
 
MICE:
Porphyrin from the Harderian glands around the eyes causes tears and nasal secretions to appear red.
 
HAMSTERS:
Hip glands, which appear as a black dot on each hip, are present in males. They are used for territorial marking and are poorly developed in females. Hamsters have a cheek pouch on each side of the inside of the mouth. Food and often baby hamsters are temporarily stored here! Hamsters are the most aggressive of all the pocket pets and often bite. Hamsters can hibernate. A sleeping hamster should be awakened carefully!
 
GERBILS:
Since gerbils are desert animals, they have a very low water requirement. Due to the low water intake, gerbils urinate small amounts. Gerbils usually mate for life; they should be paired before sexual maturity. Many gerbils exhibit mild spontaneous seizures (epilepsy), especially when startled. These usually don't require treatment. Gerbils have high blood cholesterol and lipid (fat) levels but do not show arteriosclerosis.
 
CHINCHILLAS:
Common conditions of pet chinchillas include bite wounds, respiratory diseases, overgrown teeth, diarrhea, and heat stroke.

The cage should allow a lot of movement by the chinchilla. Multilevel cages, similar to those designed by many ferret owners, work well. Like other rodents, chinchillas love to chew. Wire-mesh cages are preferred to wooden cages.Many doctors recommend covering at least a part of the floor with Plexiglas or wood in order to take some of the pressure off of the feet of the chinchilla from the wire bottom of the cage. Wood can be placed in the cage to allow the chinchilla to chew and help keep its teeth filed down.

Chinchillas require a dust bath for normal grooming. This should be provided daily and removed after use. The "dust" can be purchased at local pet stores and consists of one part of Fuller's earth and nine parts of silver sand.
 
Pocket pets can be spayed and neutered for the same reason dogs and cats are castrated. Females can develop mammary cancer and an infected uterus. Males can develop prostate disease and testicular cancer.

Information composed from: Dr. Virginia G. Brown of Goose Creek Veterinary Clinic, Dr. Donnelly, and Lifelearn Client Handouts.