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Russell Tofts
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Care of the Domestic or Fancy Rat
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Introduction
The Domestic Rat - in stark contrast to its wild cousin (and ancestor, the Brown Rat) - makes an ideal pet, being affectionate, clean, docile, intelligent, responsive, and usually most unwilling to bite. Nor do they smell when kept in hygienic conditions. What more could anyone want from a pet animal? In fact I would even go so far as to nominate it as the best pet overall! They are one of the few pets I unhesitatingly recommend for children.
It is well known that the Domestic Rat is descended from the wild Brown Rat. This pest species, which is so ubiquitous that many people view it, erroneously, as a British native, comes originally from northern China (and perhaps from other parts of Central or South-East Asia as well) but it has now established itself across the world as a human commensal. The Brown Rat had arrived in Europe by 1728 by stowing away on trading ships. It is believed to have been brought to Britain in 1730 on the occasion of a visit from the Russian fleet. The first colour mutations were being bred as laboratory animals by the end of the nineteenth century. I should add at this point that, under no circumstances, should one attempt to keep wild rats. They are aggressive, virtually untameable, and vectors for a variety of fascinating zoonotic diseases.
Breeds
There are more than 30 varieties, including Hooded, Capped, Husky, Dumbo (disproportionately large ears), Himalayan (white with dark points), Rex (curly coat and whiskers), and Sphinx (hairless abominations that should not be permitted). The Albino remains the most popular breed, probably because this is the form least reminiscent of the wild rat in appearance.
I have never been in favour of albino animals and believe that every effort should be made not to breed from animals carrying the albino gene and I would urge readers, as pet-owners, to refuse to buy albino animals of any species. An albino is a completely white animal with red or pink eyes. The bizarre (some say 'demonic') coloration of the eyes is the result of an absence of the pigment melanin, and what you are really seeing when you look into the eyes are the tiny blood vessels at the back of the eye. Since the animal, without this essential pigment, is incapable of filtering out light, bright lights can seem very bright indeed and albino animals are often destined to suffer problems with their eye-sight in later life and, in extreme cases, can even become completely blind. It is therefore unfair to continue to produce such mutations, or to encourage animal breeders or pet shops by purchasing them. Before any reader writes to me to say, correctly, that albino animals do crop up from time to time in nature, let me point out that such animals are normally 'weeded out' by predators before they have a chance to breed and so pass on their genes.
Vital Statistics
Adult weights vary according to breed and sex. Domestic Rats average about 40 cm in length, including the tail, with males (bucks) being larger than females (does). Hooded rats attain weights of 350g for bucks, 250g for does. Albinos are larger, often tipping the scales at 500-520g for males and 300-350g for females.
Habits
Mainly nocturnal or crepuscular. Excellent climbers but equally adept at burrowing. Less timid than mice, they are active, inquisitive and tame easily. Fastidiously clean, Domestic Rats spend up to one third of their waking lives indulging in auto or mutual grooming.
Diet
In the wild, most herbivores or omnivores are on a constant look-out for food. Only dedicated carnivores can afford the luxury of inactivity. In an ideal world a way would be found of proffering food to captive omnivores (such as rats) throughout their most active period. Realistically, because of time constraints on their keeper, this is not possible. I feed my animals once a day. Twice would be better. But it is very important not to feed too much at any one time, especially if the animals are being fed more than once a day, as rats that do not receive plenty of exercise are prone to obesity. As with all animals, obesity is one of the root causes of ill health and premature death. As a rough guide, rats require about 30-40g of food each day. The amount varies according to several factors: the age and condition of the rat, exercise level, if female whether she is pregnant or lactating, etc. A basic seed mixture can be given in the morning, with other foods being offered at night-time. Arguably the most omnivorous of all rodents, there is little that rats will not eat. A standard rodent mixture (ideally one designed with rats in mind, rather than an all-encompassing 'hamster' mix since the energy requirements of hamsters and rats are very different), comprising seeds, grains, cereals, broken biscuits and pellets, forms the basic diet. Alternatively you can try rabbit mix for variety. This is usually cheaper and blander, but choose one that is non-medicated, as some rabbit mixes contain a coccidiostat added at source. To this basic diet can be added various millets and canary mix, as well as small pieces of apple, banana, boiled potato, broccoli, carrot, cauliflower leaves, celery, cherries, cooked pulses, endive, grapes, kale, pear, peas, spinach, sprouts, swede, tomatoes, turnip, watercress, etc, not forgetting such garden 'weeds' as chickweed, clover, coltsfoot, comfrey, dandelion, dock and groundsel, and wild berries such as hips and haws. Green food should be given only in moderation two to three times a week and removed by the next day if uneaten.
Sunflower seeds are eaten with relish, but are fattening if fed to excess. A few scattered around the cage provides foraging activity. Unsalted peanuts and unsweetened breakfast cereals, toasted or stale wholemeal bread, millet sprays, and even live yoghurt are also appreciated, and a little cheese, hard-boiled egg, household scraps or the skin of a baked potato are welcomed as occasional treats. Rats can be given a little cooked low-fat meat (such as poultry, liver or kidney) from time to time, as well as dried cat or dog food, tinned pet food or insects such as mealworms. You can even occasionally offer a few unsalted crisps or cooked potato chips (without condiments). But the key word here is 'occasionally'. Such items are particularly useful when attempting to tame newly arrived or nervous rats. Avoid chocolate. Pregnant or lactating does can be given a little lactose-free milk (i.e. not cows' milk). This can be mixed with a small amount of wholemeal bread, cereal-based dog food, porridge, or baby rice.
Like all rodents, a rat's incisor teeth grow continually throughout the animal's life and they require hard objects on which to gnaw to prevent the teeth becoming overgrown or misshapen. Natural wood (apple or willow, for example) or cooked bones are ideal for this purpose.
Salt licks, mineral blocks and hide dog chews, all available from your local pet shop, are also useful. Clean, fresh drinking water must be available at all times, preferably in a gravity-flow bottle to prevent soiling or spillage. Keep an eye on the level in the bottle because rats, especially those fed largely on dry foods, do drink a large quantity of water. The average daily water intake is about 100g (10 ml). Rats will accept tasty morsels from your hand, but do not be tempted to offer them succulent titbits through the bars of the cage or they may in future mistake other things, passing through the bars, as food. Then you can hardly blame them if the next time you attempt to stroke them through the bars they nip your fingers. When encouraging a rat to eat from your hand, put your whole hand into the cage.
Accommodation
The cage must be as large as possible, no less than 90 x 30 x 30 cm for two rats, but preferably larger still. Unfortunately there is a dearth of good rat cages on the market. An adult rat is a fairly big and 'chunky' animal, and most of the commercially produced cages are far too small. Cages designed for hamsters or gerbils are woefully inadequate as permanent rat housing. Probably the best cage is one designed for chinchillas or ferrets. These are generally too small for their intended occupants, but make good-sized accommodation for rats. They do, however, have two major drawbacks: The distance between the bars may in some cases be too wide, allowing some rats (particularly young animals) to squeeze through. The other serious disadvantage is that chinchilla cages invariably have wire-mesh floors/shelves to facilitate cleaning. Rats that are forced to walk continuously on an all-wire surface can develop a painful swelling of the hock joint called 'bumblefoot'. It is important, therefore, that the wire mesh floor is replaced and any such shelves covered with thick cardboard or plywood to make them safer and more comfortable for the rats to walk on. This covering will, of course, need to be replaced at regular intervals.
A large glass tank makes a good home for most small rodents, but rats are the exception. They enjoy climbing, and the bars of a cage afford them the opportunity to do this which the glass sides of a fish tank do not.
More importantly, rats are very susceptible to respiratory problems (caused by infection, irritation of the lungs, or faulty genes) and a good air-flow is needed to prevent or alleviate this problem, impossible in a glass tank.
The cage should be positioned well away from draughts or direct sunlight in a dry, well-ventilated room. The ambient temperature should be maintained at between 15-25º C. Rats become sluggish when cold, and temperatures in excess of 30º C can cause heat-stroke. Think carefully about any ambient noise your rats will be exposed to. Rats can hear sounds above the level audible to humans. Some monotonous sounds might almost be classed as 'white noise' (examples include the high pitched sounds emitted by televisions, remote control devices, computers, ringing telephones, even dripping taps or squeaking door hinges), and can cause distress to the rat in constant exposure to it.
Rats enjoy the freedom of being allowed out their cage on a regular basis to explore the room, but do this only if you can remain in the room to supervise them. Cats and dogs must be banished from the room at this time, toxic houseplants removed, and exposed wiring protected. Make sure the rats cannot retreat behind heavy furniture where their quick retrieval would prove difficult.
Litter & Bedding
Traditional wood flakes are still very popular as a floor-covering, being convenient, easily obtained and inexpensive, but can be dusty and there is evidence to suggest that the dust irritates the eyes and nasal membranes. Very fine sawdust (which, ridiculously, is still sold in some pet shops as pet litter) should be avoided altogether for this reason. Pine wood and particularly red cedar are especially harmful due to the aromatic nature of the wood. Constant inhalation of the phenol oils present in this type of wood causes long-term liver damage and ultimately damage to the rat's immune system.
Some rodent-keepers remain staunch advocates of wood-based cat litters (available in the form of wood pellets). Personally I don't like this material. I find that most rodents chew it into a very fine and unpleasant powder and, in doing so, they ingest a fair quantity of it and being so desiccated it expands when it encounters the moist environment of the gut and has been known to cause impaction.
There does not seem to be a perfect litter, and everyone has his or her own preference. In the past I have experimented with a peat-substitute (very good, but attractive to mites unless scrupulous standards of hygiene are adhered to) and sand (heavy, can become quite hard and unyielding).
Recycled newspaper bedding is the one that comes closest to the ideal. Whatever material is used, have it as deep as possible (although this is not always easy in an all-wire cage). A depth of around 5 cm is not excessive. Strips of tissue paper, finely chopped straw or soft meadow hay are all suitable bedding materials (the latter will also form part of the rats' diet).
Cage Accessories
Being so intelligent, rats can easily become bored. This is one of the most challenging problems for the rat-keeper to deal with. A good cage should incorporate several levels, a stout hardboard or metal sleeping box, ladders, ropes, wooden cotton reels and other accessories. Pieces of plastic piping or cardboard tubing can be laid on the floor as tunnels, and branches arranged to provide optimum exercise potential. Special 'ratty' hammocks can be purchased from some pet shops. Large glass jars are useful - some rats will use them for sleeping in - as are cardboard boxes with the staples removed, and old woollen clothes (the smellier the better!). In hot weather it can be a good idea to include an earthenware water bowl in addition to the water bottle, so that the rats have an opportunity to wash themselves. This will help them keep cool. Very few 'toys' are available on the market for rats; most having been designed with the smaller hamster in mind. The old-fashioned spoked exercise wheel, usually made from metal, is dangerous and should never be used as it can result in trapped or broken legs and tails. A safer solid-plastic alternative does exist for hamsters, gerbils and mice, but is rarely large enough to be used by rats. In any case, the skin of a rat's tail is delicate and can be rubbed sore by the friction caused even by a solid wheel.
Change the cage furnishings frequently, so there is always something new for the rats to sniff at and generally investigate. Altering the layout of the cage every once in a while prevents them becoming bored by their surroundings.
Cleaning Out
The cage should be cleaned out once or twice a week. The bedding needs to be renewed only every ten days or so. Once a month, the furnishings should be washed in a mild detergent solution, thoroughly rinsed, and allowed to dry before being replaced in the cage. Don't wash all the furnishings at the same time, however. Retain a small quantity of the old, soiled bedding each time as this is impregnated with the rats' own scents, and will make them 'feel at home' more than will a completely sterile and disinfected cage. If the animals have been hoarding food or other items, do not remove the entire store when you clean out the cage as rats can get quite distressed upon their return to the cage to find it missing.
Compatibility
Rats being highly social creatures, it is vitally important to keep more than one. A single rat is a lonely animal. Human companionship, important though it is, is no substitute for the company of its own kind. If breeding is not the desired goal, single sex pairs will live amicably together. It does not matter which sex you choose, although males often seem friendlier. The pair should be bought at the same moment as introducing strangers to each other at a later date is not always successful and is best attempted below the age of ten weeks (eight weeks for bucks). If one animal of a pair dies, providing a companion for the one that is left can be a problem, although, in my experience, an adult animal will often accept an adolescent one - and rats are no where near as problematical to introduce to each other as are, say, gerbils and jirds, Striped Grass Mice, Steppe Lemmings, and others.
Handling
Rats benefit from regular handling sessions. It helps to keep them tame. Unlike many other pet rodents, you should not attempt to pick up a rat by its tail, for the skin on the tail sloughs easily. A rat is just too heavy to be suspended in mid-air by its tail. Picking it up by the scruff of the neck also causes it distress. The best method is to place one hand round its shoulders, so that its head lies between your thumb and forefinger, and lift it onto the palm of your other hand for support. Hold firmly but not too tightly. If you are unsure of its temperament and are concerned that it might attempt to bite, have it facing your wrist rather than your fingers, where it will have much more difficulty gaining purchase with its teeth, although, as I say, it is rare for all but the most nervous or frightened of rats to bite. Avoid sudden movement or noise.
Always handle a rat (or indeed any small animal) over the top of a table or couch, as even a short fall can result in death or maiming. A nervous animal, unused to being handle, will void droppings readily. These are wet and adhesive, so make sure any droppings that are excreted cannot spoil any valuable or delicate soft furnishings.
Adolescent rats, unused to being handled, are quite skittish, fast and nervous. This is particularly true of those purchased from pet shops, where they would not have been handled much and where they would have been subjected to the stress of being exhibited under harsh, white light. Patience is required to tame them, but it is important that they get used to being handled from the outset and do not cower in a corner of the cage the moment your hand is inserted.
Sexing
Like other small mammals, this is most easily accomplished in young rats by comparing the distance between the anal and genital apertures (this gap being much wider in the buck). Even in juveniles, the testes of the male are clearly visible (though in moments of stress, these can be withdrawn into the inguinal cavity out of harm's way, making accurate sexing slightly more difficult). Holding the animal vertically will cause the testes to fall into the scrotum, making sexing easier.
Behavioural differences are also apparent from an early age. Bucks have a coarser coat than females, with a slightly musky, but not unpleasant, smell to it. Does are more active. They have a smoother coat, with almost no discernible smell and rarely do they scent mark. Full grown males are larger and of a gentler disposition than females. Males (this will come as no surprise to women's libbers) are generally lazier.
Health
At the first sign of trouble, always consult your veterinary surgeon, although it must be said that some veterinary surgeons are much more proficient at small animal medicine than others. One of the commonest complaints is malocclusion, where the teeth are not aligned, leading to one set becoming grossly overshot. In severe cases, this condition can even prevent the animal from eating. The condition is often hereditary, so an affected animal must never be used for breeding.
Among the other common ailments to look out for are respiratory distress (characterised by wheezing, laboured breathing, nasal discharge, sneezing or coughing). This is precipitated by several factors, the chief one being a infection caused by the Mycoplasma bacillus. This unpleasant organism, which infects the respiratory system, is carried (usually unnoticed) by virtually all pet rats. In some specimens, however, the symptoms are very noticeable and, if left unchecked, may progress to a secondary infection or to bronchitis, emphysema, pneumonia or lung abscesses. Without appropriate treatment with antibiotics, permanent lung damage can result. Since the condition is inherited, it is inadvisable to breed from such animals. Other causes of noisy breathing are: an allergic reaction to fine dust particles, such as those in hay or sawdust, or to the phenol oil in wood shavings, or to what at one time used to be called a 'chill' caused by fluctuating temperatures (I'm aware that the veterinary and medical professions no longer recognise any such condition as a 'chill').
Older rats sometimes develop a head-tilt (colloquially known as 'wryneck'), frequently accompanied by head-weaving or a loss of balance. Not always a symptom of middle- (or inner-) ear disease, as is commonly thought, in extreme cases this can become so severe that the animal is constantly revolving in a circle. In a case as serious as this, euthanasia is perhaps the only course of action. It is still not always clear what has caused the head-tilt. Bacteria have been implicated in some cases and, in other instances, it is caused by a fall or some other trauma, but neither explanation can account for all occurrences of this distressing condition.
Sexual Maturity (Puberty)
8-10 weeks of age, but females as young as 3½ weeks have been known to fall pregnant. Since bucks mature slightly later than does, there is relatively little danger of females being impregnated by their litter-mates as long as the sexes are separated by the age of 5-6 weeks. It is inadvisable to allow them to breed below the age of 4 months, but, if the female has not produced her first litter by the age of 8 months, she might have difficulty during labour when she does become pregnant.
Oestrus Cycle
Every 4-5 days throughout the year. Females are polyoestrous, although they seldom come into 'heat' without the companionship of a male. A female remains in oestrus ('in season') for approximately 12-14 hours, during which time she may appear more jumpy or skittish than is normal. She may 'freeze', arch her back or flutter her ears if her haunches are tickled at this time.
Mating
Mating is quick, lasting only a few seconds. Males produce a hard-setting seminal fluid. A plug of ejaculate forms in the female's vagina, effectively sealing off the vestibule. The purpose of this is to prevent entry to competing sperms from rival male rats. This vaginal plug shrinks and falls out after 12-24 hours.
Gestation Period
20-23 days
Young (Pups)
The buck can safely be left with the doe after mating as he will not harm the young under most circumstances. However, since females are receptive and ready to be mated again within 12 hours of giving birth, it is advisable to remove the male until at least 2 weeks after the young are weaned, or the female will be impregnated again almost immediately. No animal should be bred to exhaustion. Rats are prolific breeders, and some thought must be given to what you will do with the offspring before you decide to breed your rats. Will you be able to find caring homes for them all?
A few days prior to parturition, the pregnant female prepares a cosy nest for her babies. Most births occur at night. Between 6-16 pups (average of 10, but on rare occasions there can be as many as 20) are born naked, blind, deaf, and helpless. Each weighs just 4-5 grams at birth. As a general rule, the smaller the litter, the larger the pups. Disturb them as little as possible at this stage and certainly do not be tempted to touch them, as interference of the young within the crucial first 2-3 days may cause the mother to resort to cannibalism, although this unpleasant habit is not as common as is sometimes claimed. Hair begins to appear by the 4th day. Eyes open at 13-16 days; the young are taking solid food and starting to explore their surroundings at around the same time, and they are weaned at 4-5 weeks. The young should not be removed from their mother below the age of about 5-6 weeks.
Breeding Life
12-14 months. Domestic Rats are at their most fertile between the ages of 3 and 10 months. The female enters the menopause before the male.
Life Span
2-3years. Exceptionally rats can live up to 6 years or even longer, but such murine Methuselahs are extremely rare. An old rat is distinguished by its larger size, dull coat and rough scaly tail. Many older rats succumb to the various cancers to which they are particularly prone. The main reason for this is that most pet rats are descended from laboratory animals which are bred for their predisposition to tumours and these deleterious genes are still present in the pet animals that are descended from them. Males tend to live a little longer than females, possibly because two of the commonest causes of female mortality are mammary and uterine cancers, as well as pregnancy and the rearing of young being physically exhausting processes.
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