Thames Valley Rodents

mastomys natalensis

Alternative names:

Latin name: Mastomys natalensis

Natal rat, African soft furred rat, natal multimammate mouse, and soft furred mouse.

It is a common misconception that multimammate mice are rats but these rodents in my opinion have far more in common with mice and I consider them to be such.

They are roughly two to three times the size of an average fancy mouse (weighing between 65 and 75grams compared to the 40 to 50grams of a fancy mouse).  Nowhere near rat sized!

The wild colour is an agouti brown with a paler belly. Their common name (multimammate mouse) literally means many-breasted mouse. They can have up to 18 nipples and often have odd numbers. It is fairly crepuscular in its waking habits and is generally active at random intervals throughout the day and night.

This species has been used as an object of study in labs for many, many years but has only relatively recently been introduced to the pet trade.  They are mostly kept by herptiles breeders who use them as a feeder species since they grow fast and produce large numbers of babies in each litter. The species seen most often today is mastomys natalensis and is one of the most common rodents out in its native Africa where it is considered a pest species. A similar and closely related species (mastomys coucha) was kept extensively in labs to study the effects of the Lassa fever virus but is now almost never seen in captivity. In captivity the multimammate mouse can live to be more than three years old although its average life expectancy is around two years. As with all animals, breeding females tend to have a slightly shortened life span. A real attraction of this species is that unlike fancy mice (mus musculus) even the males have no obvious odour.

Feeding:

This species is very omnivorous and should be fed quite a broad diet.

TVR’s multi’s are kept on a diet consisting of pig pellets (these are a great omnivore complete diet containing cereals, vitamins and protein from Soya. Steer clear of the pellets that include meat products), micronized peas, flaked maize, millets, safflower seeds, pumpkin seeds, corn flakes, dried and cooked pasta, vegetables and some fruit, they seem to particularly like carrot and pear. I have found that feeding them on cabbage makes them smell and that too much fruit makes them fat so it’s not always easy to strike a balance between a varied diet and a fattening one.

Sunflower seeds should only be fed sparingly as in my opinion the can exacerbate the growth of tumours and lead to obesity which has complications of its own including infertility and heart problems.

Every now and then some live foods can be given e.g. crickets, mealworms. Wax worms are a great way to put weight on youngsters that have just weaned, females that have recently littered and sick animals but shouldn’t be fed to healthy adults more than very occasionally, as they are very high in fat.

As with all of TVR’s rodents, the multimammates are given hard, baked bread to gnaw on as well as porridge and rice.

Breeding:

Breeding multimammate mice is extremely easy. It is best to start with an unrelated trio - two unrelated females and a male that is unrelated to either of them. This means that your first generation of babies from each female will be only partially related to one another and can be bred together safely. It is best to introduce the animals when they are still fairly young because although I haven’t had any problems with aggression from my animals, some people have experienced terrible territory disputes (from mice of other blood lines to mine) when introducing adults that are unknown to one another.

Multimammate mice feed their babies on what is known as the ‘aunty system’ where by females in the colony will feed any babies regardless of whether they are hers or not. In some instances the female will not even need to get pregnant herself in order to lactate for another females offspring. It is down to this strong maternal instinct that the species owes its success and ultimately is what has led it to become such a pest in Africa.

Housing:

This is a species that will eventually chew out of anything that isn’t made of metal or glass and for this reason I keep mine in old glass aquariums with tightly fitting lids. I have tried to keep them in various cages but they always chew out eventually. Keep the tank filled with different sized branches and twigs to give them something to climb on and to keep their teeth occupied.

I always use brands such as AubiousÔ or BlissÔ as a substrate and never use wood shavings. Aspen shavings would be another suitable option as would peat. If using peat make sure that it is dry before putting it into the tank otherwise it will condensate and cause respiratory problems.

Handling:

I always pick up an unknown multi by the base if its tail and then quickly place it on the palm of my hand. There seems to be little that these creatures fear and they have a not entirely unjustified reputation for being vicious towards the handler. I hold that multi bites are some of the worst you can receive from a rodent.

I have found that unless used to being handled multimammate mice hate being picked up round the middle as you would a Syrian hamster. Cupping your hands around the mouse to lift it up seems less likely to cause it to bite. After many generations of selectively breeding for temperament mine are now very unlikely to bite unless caught by surprise or heavily pregnant.

Colour mutations:

Multimammate mice are now seen in quite a variety of colours including the natural agouti brown (AA). Note: genetic symbols are for demonstration purposes only as there is not to my knowledge any clear-cut genetic information available on the multimammate mouse.

Cinnamon: (aa) similar to agouti but lacking the black ticking to each hair and so has a much paler look to the fur. I believe this to be a recessive gene.

Pied: any colour with large patched of white. This appears to be a co-dominant gene as whenever I have bred a pied to a self coloured animal I gets both pieds and selfs cropping up in litters. There are two distinct markings seen in pied animals – white animals with saddles of colour across the back and coloured animals with a white blaze or ‘badger’ marking on the face. Again I get both occurring in litters.

Red-eyed cinnamon (rr): sometimes referred to as champagne or argente, it is a very pale cream with a slate grey under coat and bright pink eyes. As it is a recessive gene all red-eyed animals are homozygous and cannot carry any other genes. Red-eyed carriers (heterozygous agoutis) have a colouration similar to that of a cinnamon but are still agouti.

If you breed a red eyed to a black eyed carrying the red-eyed gene you will get 100% visually agouti youngsters which are heterozygous for the red eyed gene.

If you breed a mouse that is heterozygous for the Red eyed gene to a homozygous agouti you will get 50% homozygous agouti and 50% heterozygous agouti carrying the red eyed gene

If you breed two heterozygous agoutis that are carrying the red eyed gene you will get 25%homozygous agouti, 50% heterozygous agouti carrying the red eyed gene and 25% homozygous red eyed animals.

If you breed a heterozygous agouti to a homozygous red-eyed animal you will get 50% heterozygous red-eyed carriers and 50% homozygous red-eyed animals