Pet Rat & Mouse Care: What Every Owner Should Know
Rats and mice are among the most rewarding small mammals to keep. The fancy rat (Rattus norvegicus) is originally from northern China and is a genuinely social, intelligent animal: in the wild it lives in large, male-dominated groups with a clear pecking order, and it forages mostly at night or at dusk using an excellent sense of smell. A full-grown Norway rat reaches about 400 mm nose-to-tail and weighs 140–500 g, with a tail shorter than its body. Fancy mice (Mus musculus) are smaller, 65–95 mm long with tails of 60–105 mm. In captivity a mouse typically lives about two years and occasionally as long as six, while wild house mice rarely survive beyond 12–18 months. Both species are social and do best with company of their own kind.
Housing
The single most important rule for caging is that the enclosure must be chew-proof and easy to clean. Rats and mice will gnaw through weaker materials, particularly in the corners, so the structure needs to be indestructible to rodent teeth. Solid floors are strongly preferred. Wire-mesh floors should be avoided because small feet — especially the hindlimbs — slip through the openings and suffer fractures and other injuries. Because ammonia from urine builds up quickly and aggravates respiratory disease, appropriate bedding plus frequent cage cleaning are essential to keeping these animals healthy.
Health
Rodent teeth never stop growing. Pet rats and mice have continually erupting incisors, and the most common dental problem in these species is simply overgrown incisors — worth noting because in guinea pigs and chinchillas the opposite is true, where cheek-tooth malocclusion dominates. Watching for changes in eating or drooling is the practical takeaway.
The most common subcutaneous tumor in rats is the mammary fibroadenoma. Because mammary tissue is distributed extensively from the neck down to the groin, these tumors can appear almost anywhere and can reach 8–10 cm across; they occur in both males and females, so sex is no protection.
A more serious concern is rat-bite fever. The bacterium Streptobacillus moniliformis lives harmlessly in the rat's own nasal and throat flora and causes the rat no disease, but a person bitten by a rat can become infected and develop a potentially fatal illness. Thorough hand-washing after handling and avoiding bites are the sensible precautions.
A Note on Sourcing
Under the U.S. Lacey Act (50 CFR 16.11), certain live mammals are prohibited from import — the list includes the multimammate rat and several other wild species. This does not affect domestically bred fancy rats and mice, but it is the legal reason to source pet rodents from reputable local breeders rather than the wild or unknown supply chains.