Spiny mice

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Spiny mice
Egyptian spiny mouse (Acomys cahirinus)

Egyptian spiny mouse
( Acomys cahirinus )

Systematics
Order : Rodents (Rodentia)
Subordination : Mouse relatives (Myomorpha)
Superfamily : Mice-like (Muroidea)
Family : Long-tailed mice (Muridae)
Subfamily : Deomyinae
Genre : Spiny mice
Scientific name
Acomys
I. Geoffroy Saint-Hilaire , 1838

The spiny mice ( Acomys ) are a genus in the family of long-tailed mice .

features

The different species of spiny mice are about the size of house mice , have a head body length of 7 to 17 cm and a tail that is 5 to 12 cm long. On the top they are yellowish, brown or gray. On their back they have coarse bristle hairs, the spines . They have noticeably large and upright, funnel-shaped ears and an elongated face that becomes even more pointed towards the nose.

distribution

Spiny mice inhabit sandy and rocky regions in numerous species and subspecies in Asia Minor and Western Asia as far as Pakistan , Africa , Crete and Cyprus . Their taxonomy is complicated, most of the species can be crossed to a limited extent depending on their place of origin, the numerous subspecies have recently formed hybrid forms, since the spiny mouse spreads as a cultural follower in different, poorly investigated ways. The animals available in pet shops in Europe are almost always mixed breeds of different subspecies.

Systematics

Acomys cilicicus (Turkish spiny mouse) in the all-weather zoo in Münster

The position of the spiny mice in the rodent system is so controversial that they are sometimes completely removed from the Old World mice , Wilson & Reeder (2005) classify them in the Deomyinae subfamily . The following 14 types are distinguished:

Sometimes the Cape spiny mouse is separated as a further subgenus Subacomys . The Sinai spiny mouse ( Acomys dimidiatus ) is not accepted by the majority of zoologists as an independent species, but rather as a variant of the Egyptian spiny mouse. There is also a theory according to which the Cretan spiny mouse was introduced by humans in Crete and therefore cannot be an independent species.

Denys & al. In 1994, after extensive research, three more species were established:

Way of life

Spiny mice usually live in groups and have quite a developed social life. Foreign conspecifics are mostly not tolerated and are killed. Some species, such as the Egyptian spiny mouse, are interesting from a behavioral point of view due to their high resistance to social stress . Even with a high density of individuals, they show no aggressive tendencies towards family members and are therefore easy to keep. Cannibalistic behavior occurring in captivity (the typical pecking at tails, especially at the base of the tail) is not related to density in these animals, but can be an indication of malnutrition or a disruption in the natural sleep-wake cycle.

Most species are straightforward to breed. Spiny mice aren't picky. After a gestation period that is considerably longer than that of other mice - it lasts around 35 to 38 days - up to five already developed young are born per litter. The male is present at birth and protects the entrance to the nest and moves close to the female when it is cold to warm it and the young. The young are not only cleaned of the amniotic sac and licked by the mother, but also by other female animals and the father.

The little spiny mice are fleeing nests , which are already fully hairy including the bristle hair and are born with already broken incisors. Except for the Cretan spiny mice, their eyes are already open, they learn to walk relatively quickly and move around in the community.

Spiny mice only have four teats - however, surplus young are easily adopted by other females. The same happens when the young lose their mother. The young are suckled for just under three weeks; however, if the mother is lost, a week is sufficient. The young animals usually begin to be interested in solid, species-specific food on their birthday and eat it regularly after six days at the latest.

The food is mainly vegetable and is usually sought at dusk and at night. However, insects, snails and other animal foods are also eaten to enrich the diet. Spiny mice also occasionally take on carrion and look for dead or dying larger animals in order to feed on them. Dried out fur residues from dead animals are eaten and used to build nests. However, the animals are very clean and spend a lot of time cleaning. When feeding in captivity, particular attention should be paid to a diet that is low in nutrients and low in fat. The animals are frugal by nature.

Nest building

The nest-building behavior is rather sparsely developed compared to mice from temperate zones. They use natural shelters, crevices in the rock, holes under stones, which are rarely dug themselves. Occasional repair work occurs, mostly at the entrance. Inside, the mice accumulate food components and grass over time, but there is no building of woven nests or padding.

Spiny mice gnaw little. They widen holes and gaps in wooden walls slightly, but do not create any new openings and do not show any activities in the natural environment in places where it does not bring them any advantages.

biology

Bristle hairs of the spiny mouse

The coarse, spiky bristle hairs ( spines ) are created by merged follicles and consist of a soft, flexible hair structure that corresponds to hair that has grown together. Depending on the species, they cover the entire back, but always an outlined, well delimited, sometimes circular area that overhangs caudally. The spines do not appear outside of this area: the flanks, stomach and head are usually very softly haired.

The evolutionary biological use of the bristle hair has not been clarified. They appear slightly rebellious in the throat of snakes, but offer no protection that would be comparable to that of hedgehogs. Snakes are generally not afraid of spiny mice. The spines could also come from a sexual selection , which would be plausible with regard to their clearly defined distribution. Corresponding preferences in partner choice have not yet been proven.

Autotomy

Two species of African spiny mouse, Acomys kempi and Acomys percivali , can counteract attack by predators through their skin, which can be stripped off without great resistance. This makes them the first mammals to have autotomy demonstrated.

All layers of the lost skin can be completely regenerated with little to no scarring including hair follicles, sweat glands and other things. These properties are currently being investigated for application in human wound healing.

Behavioral Biology in Captivity

Corrupted body parts are an expression of a disturbed daily rhythm

The spiny mouse makes special demands on temperature and light. It needs a significant temperature fluctuation, otherwise its day-night rhythm gets mixed up and social behaviors, which are probably related to the REM sleep distribution, change unnaturally. Lots of light during the day and up to 35 ° C, at night the temperature should be reduced to below 10 ° C (Cretan or Cypriot spiny mice), and up to 4 ° C for African mice. In this environment, the mice show their natural behavior. Where this is not possible, mutual eating must be expected even with only two mice.

Changes in behavior occur in environments that do not correspond to the natural environment:

  • The disturbed daily rhythm is also evident:
    • in an increased willingness to rest, which is characterized by constant interruptions of activity during activity phases through REM sleep phases, during which the animals remain motionless in a crouching position without going to their shelter or showing preparatory behavior
    • in activity and rest phases that are differently distributed over all mice and that normally have to coincide
  • Undertrained by easily accessible presentation of the food leads to apathy and boredom. The grains and seeds want to be found scattered on the ground by searching and digging. An increased urge to gnaw is also a sign of insufficient demand.
  • Overfeeding the very frugal animals with fatty seeds or mealworms leads to obese and phlegmatic animals. Occasionally there is a change in the sequence of movements, the animals walk short distances in a crouching position and often remain in place.
  • Soft, woody or grassy soils lead to increased humidity and often to bacterial diseases such as pneumonia and organ mycoses , but also chronic, subclinical infections. A stony, sandy, dry or hygroscopic soil ( cat litter ) is more suitable for the animals. Behavioral signs of subclinical infections are:
    • Changes in cleaning behavior
    • a motionless, sideways or swaying gait in a squatting position, changes in the sense of relieving postures
  • The crossing of different subspecies or species leads to the appearance of atypical behavior patterns. A meaningful behavior observation is then not possible. Almost all commercially available mice come from impure breeding lines , as they come from different private hands and not from the area of ​​distribution. The lines kept in zoological gardens are also not pure if lines of unclear origin are used to refresh them. Notes on contaminated breeding lines:
    • The coat color of adult mice varies.
    • The bristling varies between individuals or is not clearly delimited from the rest of the fur on an individual in terms of area.
    • Significantly varying behaviors within a gender. (Escape behavior, protective behavior, social activities, noise habituation, food preferences, daily rhythm)

Excess mice can be fed, but can be dangerous for smaller snakes.

Spiny mice and humans

In Egypt, the Egyptian spiny mouse has become a cultural follower , which, like the house mouse in Europe, penetrates buildings and acts as a pest.

Some species are becoming increasingly popular as pets. Due to their insensitivity to stress, they are quite easy to keep in the domestic area. However, keeping them appropriately is problematic and requires some experience. Errors are particularly noticeable through behavioral changes and disorders, while reproductivity and life expectancy are not significantly changed.

Spiny mice generally flee from humans, but they quickly become trusting. Specimens that already had contact with hands and background noise as young animals show no shyness and accept food that is held out, but do not have any social relationship with the human hand and always remain wild animals.

Prickly mice are unsuitable for cuddling purposes, as they not only have no social relationship with humans, but are also unpredictable and can bite very painfully. In contrast to other rodents, no warning or test bites are initially taken, but are bitten through deeply immediately. The bite occurs in one go, takes about a second and then triggers an effort to escape . In particular, there is no subsequent biting. Even when handling hand-rearing, there is a certain, lower probability of sudden and apparently “unfounded” bites that can reach the fingers through gloves to the bone - but these trusting specimens do not make any effort to escape. This behavior is obviously not induced by fear, because the animals then remain calm and go about their other activities. In addition, spiny mice that appear very healthy occasionally transmit diseases, mostly bacterial infections and toxoplasmosis .

literature

Web links

Commons : Acomys  - collection of pictures, videos and audio files
  • rodent-info.net Basic information on the genus with pictures of individual species

Individual evidence

  1. ↑ Ashley W. Seifert, Stephen G. Kiama, Megan G. Seifert, Jacob R. Goheen, Todd M. Palmer, Malcolm Maden: Skin shedding and tissue regeneration in African spiny mice (Acomys). In: Nature. 489, 2012, p. 561, doi: 10.1038 / nature11499 .
  2. ↑ Zoe Cormier: African spiny mice can regrow lost skin , Nature . September 26, 2012. Retrieved September 27, 2012.