Brown Rat

Overview

The brown rat (Rattus norvegicus) is one of the most widespread mammals on the planet, found on every continent except Antarctica. Pet rats - often called fancy rats - are a domesticated subspecies, known as Rattus norvegicus domestica, produced through selective breeding of the wild brown rat.

In the wild, brown rats typically have brown or dark grey fur with lighter underparts. Their body can measure up to 28 cm long, with a tail slightly shorter than that, and they can weigh anywhere between 140 and 500 g. Your pet rat may sit at the heavier end of that range, since large individuals are more commonly seen in domestic specimens.

Despite the scientific name Rattus norvegicus suggesting Norwegian origins, the brown rat is actually thought to have originated in northern China and neighbouring areas. The misleading name was popularised by an 18th-century English naturalist who believed the rats had arrived on Norwegian ships - a mix-up that stuck!

Temperament & behaviour

Fancy rats are sociable animals that naturally live in large groups with a clear social order. They enjoy grooming each other and sleeping together, so keeping rats in pairs or small groups generally suits them well.

Rats love to play. Groups will chase, tumble, jump and engage in friendly wrestling - this is completely normal behaviour. You may also notice your rat making a clicking or burring sound called bruxing, which is teeth-grinding often linked to happiness. Sometimes bruxing is accompanied by boggling, where the eyes appear to rapidly bulge and retract - this looks alarming but is simply caused by jaw muscle movement.

Rats can also produce ultrasonic vocalisations too high-pitched for human ears. A chirping sound made during play or tickling has been compared to laughter and is associated with positive emotions. Bat detectors are sometimes used by pet owners to hear these sounds. Rats may also squeak audibly across a range of tones depending on how they are feeling.

Brown rats are naturally nocturnal, are good swimmers, and are known to be skilled climbers and diggers. Expect your pet rat to be curious and active, especially in the evening.

Care basics

Rats are true omnivores and will eat almost anything, but cereals form a substantial part of their natural diet. Favourites noted in studies include scrambled eggs, raw carrots and cooked corn kernels. Foods such as raw beets, peaches and raw celery tend to be less popular with rats.

Because rats are social and live in hierarchical groups in the wild, they generally thrive with company. Providing opportunities to dig, climb and explore reflects their natural behaviour - brown rats are known to excavate extensive burrow systems and are capable climbers.

Rats reproduce very rapidly - a female can produce up to five litters a year, with litters commonly numbering around seven pups. If you keep males and females together, be aware that breeding can happen quickly and frequently. Keeping same-sex groups is a straightforward way to avoid unexpected litters.

Health awareness

The maximum recorded lifespan for a brown rat is three years, though many do not reach this. Being aware that rats have relatively short lives helps owners make the most of their time together and stay alert to any changes in health or behaviour.

Rats have a naturally fast heart rate of around 300 to 400 beats per minute and a respiratory rate of around 100 breaths per minute. Any noticeable changes in breathing or unusual lethargy are worth keeping an eye on and discussing with a vet who has experience with small animals.

Rats have fairly poor eyesight - their vision is quite limited compared to humans, and they perceive colour in a way similar to red-green colour blindness in people. This means they rely heavily on their highly developed sense of smell and acute hearing to navigate their world. Sudden changes in their environment may be more disorienting for them than you might expect.

As with any pet, regular handling helps you notice early if something seems off - changes in weight, coat condition, appetite or social behaviour can all be useful signs that a vet check-up might be a good idea.

This is general awareness only, not veterinary advice. Always consult a vet about your pet's health.

Fun facts

Rats can see ultraviolet light that is completely invisible to humans, thanks to UV receptors in their blue-light vision system. The world looks quite different through a rat's eyes!

A 2007 study found that brown rats appear to possess metacognition - an awareness of their own mental states - a ability previously associated only with humans and some other primates.

That chirping sound rats make during play and tickling is interpreted by researchers as an expression of positive emotions and even anticipation of something rewarding. Rats that are tickled regularly become conditioned to seek out the tickling - so your rat really might enjoy a good tickle session.

The brown rat has gathered quite a collection of nicknames over the centuries, including the common rat, street rat, sewer rat, wharf rat, Hanover rat, Norway rat and Norwegian rat - not bad for an animal that originally came from China!

Source

Adapted from Wikipedia (CC BY-SA 4.0): https://en.wikipedia.org/wiki/Brown_rat