Spiny Mice

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Introduction

As the name suggests, the pelage is modified into coarse, rigid grooved bristles or spines that do seem to offer the animal a certain amount of protection from its many predators. It is claimed that owls, in particular, are thwarted by this line of defence, though I fail to understand the reasoning behind this, as one would think that an owl's talons would prove more than effective. I have a theory that the hairs are not rigid or painful enough to stop the animal being taken by predators, including Caracals and Fennec Foxes, but when the carnivore swallows the luckless animal, the inflexible spine-like hairs cause severe irritation to the lining of the throat, and it knows to avoid Spiny Mice in the future. This, obviously, is no consolation to the one that has been ingested, but it does bring protection to the colony as a whole.

There are 5-10 species in the genus Acomys (sources fail to agree exactly how many; see comments below) but, of these, only two kinds (Acomys cahirinus and Acomys russatus) are regularly available in Britain at the moment, of which the one most often encountered is arguably the "Cairo" Spiny Mouse (Acomys cahirinus). Despite its name, which implies a rather localised range, it has a wide distribution, but was given its misleading vernacular name from specimens found in the Cairo area of Egypt at the beginning of the 19th century. The comments in this article refer mainly to this species, but can be applied to all other species as well.

A member of the typical mouse family, the Murinae, the various species of Spiny Mice are distributed from East and South Africa, through the Near East to Asia Minor. The genus presents a confusing puzzle: since there is so much variation within each population, it is not clear exactly how many species exist, or whether all the recognised species are truly full species in their own right or merely subspecies. Most authorities recognise the following eight species:

  • Acomys cahirinus (Mauritania to southern Pakistan and Tanzania, Crete, Cypress)
  •  * Acomys cilicius (Asia Minor)
  • Acomys louisae (Ethiopia, Somalia)
  • * Acomys russatus (north-eastern Egypt, Palestine, Jordan, Arabian Peninsula)
  • Acomys spinosissimus (Tanzania, Zambia, Zimbabwe)
  • Acomys subspinosus (south-western South Africa)
  • Acomys whitei (Oman)
  • Acomys wilsoni (south-eastern Sudan, southern Ethiopia, Kenya)

(*asterisks denote species known by the author to be presently maintained in captivity in Britain. He would welcome information on the current captive status of the remaining species)

The vulnerable Cretan Spiny Mouse (Acomys cahirinus minous), considered here as a subspecies of Acomys cahirinus, is occasionally given full species status by some authorities. Found wild in Crete and Cyprus, it is believed that it may have been artificially introduced onto these islands where, separated from the mainland population, it eventually acquired certain phenotypic differences, notably being greyer in coloration with a more pointed face. The Turkish Spiny Mouse (Acomys cilicicus) can be seen at Marwell Zoological Park, Hampshire, Great Britain, and Bristol Zoo which are participating in a breeding programme to save it from extinction. 

Similarly there is some debate as whether the "Arabian" Spiny Mouse (Acomys cahirinus dimidiatus) should be considered a full species in its own right, or is merely a larger and paler subspecies of the "Egyptian" Spiny Mouse (Acomys cahirinus cahirinus). Zoologists also fail to agree whether the melanistic form of Acomys russatus should be considered as a separate species. Clearly there is a lot of work to be done in this area, but clarification is needed urgently to prevent hybrid animals being produced.

Spiny Mice inhabit arid regions, including semi-desert, dry woodland and savannah. Favoured shelters include rocky crevices, cracked soil, gerbil burrows and termite mounds. Largely terrestrial, they are, like most rodents, adept at climbing when necessary and have been found, on occasion, sheltering in trees. Acomys cahirinus can also be found in and around human habitation.

Feeding

They are omnivorous and, in parts of Egypt, Acomys cahirinus has even reputedly feasted on the mummified corpses of the pharaohs. In captivity they feed on a standard rodent mixture of seeds, nuts and cereals. Like many other rodents, live food is important, particularly crickets or locust hoppers. Meal-worms, too, are a useful dietary addition but should be fed fairly sparingly because they are deficient in calcium. A few meal-worms once or twice a week is fine though.

Treats can include an occasional piece of apple or carrot, dates, corn-on-the-cob, small quantities of green food (too much "scours" the stomach), wholemeal bread, or dog biscuit. Sunflower seeds are enjoyed, but can be fattening if fed to excess. As with all animals, obesity will shorten life expectancy and inhibits breeding potential. Meat (and even bones on which to gnaw) is also relished.

Hailing from fairly arid regions, their digestive system has evolved to extract the maximum amount of moisture from their food. However, in captivity water should be available at all times, either in a shallow open dish or in a bottle.

Housing

Spiny Mice are best kept in a large glass aquarium with a well-fitting but well-ventilated lid, and plenty of cage furnishings to keep them occupied in the form of branches from fruit trees, rocks, plastic pipes, cardboard rolls, jam-jars, partially-submerged earthenware flowerpots to simulate burrows, and plastic or wooden "houses". A handful of clean, dust-free hay is always appreciated as it introduces new and interesting scents into the enclosure. I don't believe in the use of exercise wheels for any long-tailed rodent.

The litter can be coarse wood-chips (not sawdust, which is too fine and irritating to the mucus membranes), peat-substitute such as Coir fibre (not real peat, please, because of the continuing degradation of the ancient peat bogs), or silver sand. A new substrate increasing in popularity are the various brands of wood-based cat litter (usually occurring in pellet form). I have severe misgivings about these, as small animals tend to chew the pellets into an extremely fine, unpleasant dust. Not only is the dust bad for the eyes, lungs and nasal membranes, but inevitably particles are ingested. Being so desiccated, there is a danger that the swallowed particles may expand when they encounter the moister conditions of the elementary canal, stomach and intestines.

The cage should be stood in a fairly warm room, away from direct sunlight. Normal room temperature is fine but, if kept in a shed or similar outbuilding, additional warmth may need to be provided in the winter because Spiny Mice cannot tolerate cold or damp conditions.

Spiny Mice are – as I know to my cost, having lost a couple of escapees – fast and prone to jumping erratically if panicked, so special care should be exercised when trapping individuals or during routine cage-cleaning. They do become calmer in time, when they have settled down.

The various species are communal and do best in colonies. Specimens kept singly rarely thrive. Nipping of ears and tails and, in extreme cases, flayed backs are signs that the colony is overcrowded and/or contains an over-abundance of males. Introducing strangers to an established colony is almost impossible, and serious fighting usually results.

Behaviour

Although essentially nocturnal, Spiny Mice do nevertheless have bouts of activity during the day, particularly in the early morning and late afternoon. Acomys russatus (the "Golden" Spiny Mouse) is largely diurnal in its native Arabia and, for this reason, can tolerate higher temperatures than can the other species.

Spiny Mice can become quite trusting (I hesitate to use the word "tame" when referring to truly wild animals), but handling is quite stressful and I generally handle only when necessary. Remember that they do possess sharp needle-like teeth (ideal for eating insects) and, if it feels threatened, a Spiny Mouse can deliver quite a painful bite, although it is reported that they are relatively easy to "hand-tame".  

The tail is very brittle and, if the animal is grasped by this appendage, it will spin and the tail may be partially or completed lost (see my comments about autonomy in the sections on Degus and African Dwarf Dormice).

Breeding

Sexing is relatively straightforward, particularly for mature animals, the anal-genital distance being greater for males.

Spiny Mice are one of the few animals known to adopt the "nanny" system, whereby a female will nurse babies which are not her own. Females give birth in a standing position in the hub of the colony, rarely retiring to be on their own during this delicate time. Acomys cahirinus makes no attempt to build a nest, although some other species, notably Acomys russatus and Acomys spinosissimus, are known to fashion rudimentary nests from hay, grass or leaves. The young (usually 2-3, but on rare occasions it can be as many as 5) are born after a gestation period of 35-45 days, and (not surprisingly for an animal with a relatively long gestation) the young are quite precocious, being fully furred at birth (infants are pearl grey at first) and mobile after just 24 hours. Unusually for a rodent, the young are often delivered backwards, more reminiscent of the large hoofed animals. Eyes and ears open at birth or soon thereafter. They develop quickly, can be seen to be nibbling at food after just one week, and are independent at 2 weeks of age, although I do not remove them from the dam below the age of 3 weeks. They attain sexual maturity at 45-60 days and are fully grown at 6 months. A female is often re-mated almost immediately after giving birth. Breeding is continuous throughout the year, with little seasonal variation, which may explain why, in general, females do not live quite as long as the males, and it is not unusual for a female to have 12 or more litters in quick succession. Unlike some other rodents, in the wild they do not appear to time their breeding activity to coincide with favourable climate or food availability.

I have enjoyed considerable success with three different subspecies, but other breeders I have spoken to have suffered cases of high infant mortality, the young usually being found quite badly mutilated. It is never clear whether the terrible injuries were the cause of death or occurred  post-mortem, as Spiny Mice will usually mutilate a body after death. I ascribe abnormally high juvenile mortality to two factors: the cage may be too small or there is a lack of privacy. My Spiny Mice live in large tanks and have access to a number of wooden nest-boxes (although, as I say, they do not "nest" in the conventional rodent way) and other areas of cover, and my neonatal mortality rate is generally zero. 

Life span ranges from 2-3 years (relatively long for a “mouse”), but record longevities of 5 years have been recorded on occasion, with males generally outliving females.

Several sources record that, just before the death of a Spiny Mouse, the animal experiences rapid weight loss, to the point of becoming slightly emaciated.

By Russell Tofts