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Acomys russatusgolden spiny mouse

By Benjamin Fishman

Geographic Range

Golden spiny mice inhabit a limited region of the Middle East and Africa. Until recently they were found only in the northeastern portion of the Egyptian desert and in the southern Sinai of Saudi Arabia (Harrison and Bates 1991). Golden spiny mice have now been discovered inhabiting the present day regions of Jordan, Israel, Yemen, and Oman (Nowak 1999). Species of the genus Acomys are all found in arid regions from the eastern Mediterranean to Pakistan.

Habitat

Golden spiny mice live in arid regions consisting of deserts and savannas dominated by rocky crevices. A. russatus take up residence in terrain consisting of dried up river beds and hillsides strewn with boulders (Kronfeld et al. 1994). Here, they can squeeze between crevices and remain protected from predators. The color of their pelage further aids in blending into the arid landscape. Spiny mice don't typically have a family home, but live in a small community with other A. russatus. These communities are not evenly distributed, but located near food sources. In areas where human habitation exists, A. russatus communities are dense, especially due to agricultural food sources (Haim and Rozenfeld 1998). It has been suggested that, since A. russatus are passive, through time they have been forced into living in arid environments due to competition/exclusion by other more dominant rodents (Kronfeld et al. 1994).

Physical Description

Acomys russatus are light golden brown in appearance on the dorsal surface. The ventral side is white in color however, the entire pelage of this species is bristly with individual, non- prickly spines covering the animal. The bristles tend to be thicker and more abundant dorsally. The ends of the spines are black or grey which gives this species a more light brown appearance instead of bright gold. A single white patch is found below each eye and behind each ear. The dorsal sides of each limb contain a small white patch as well. Average body and tail lengths are 7-15cm. and 4-13cm., respectively (Grzimek 1990). There is slight sexual dimorphism in size.

  • Range mass
    15 to 80 g
    0.53 to 2.82 oz
  • Average mass
    45 g
    1.59 oz
  • Average basal metabolic rate
    0.24 W
    AnAge

Reproduction

This species is capable of breeding throughout the year, however breeding peaks during the wet season from February to July. First litters are small, only one or two young are born. Older females can give birth to litters of four or five young. Gestation periods last 5-6 weeks, unlike most murids where gestation is approximately 3-4 weeks long. This results in Acomys russatus newborns being very well developed. These young are not hairless, blind, or helpless like most mice (Grzimek 1990). They require very little warming by the mother, newborns can maintain constant body temperatures. This may be an adaptation to living in an arid climate (Harrison and Bates1991).

Young spiny mice are born in the presence of numerous females. These females will help the mother by licking and cleaning the newborn and disconnecting the umbilical cord. Other lactating females will attempt to steal and adopt these young as their own. No fighting occurs, and this "policy" seems to be understood within the species. Thus in essence, newborns are the "property" of all nursing females within a community (Grzimek 1990). The male's role is not significant. He can be found guarding a nest site and finding food during the first few post-natal weeks. Parental care mainly occurs by the mother(s) in charge. Within 3 months the newborns are on their own and sexually mature. Typical lifespan is around 3 years.

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)
  • sexual
  • Average number of offspring
    2.5
    AnAge
  • Average gestation period
    34 days
    AnAge
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    91 days
    AnAge

Behavior

The golden spiny mouse is a non-aggressive rodent. When in danger or alarmed, it outwardly projects its bristly spines in order to make itself appear larger to a predator. A. russatus also have specialized behavioral and physiological adaptations which allow them to survive in extreme arid conditions (Degen 1994). Because of an omnivorous diet, sufficient water requirements are met which allow for evaporative cooling during the daylight hours. Furthermore, the golden spiny mouse has a low metabolic rate which minimizes food needs and lowers internal heat production thereby promoting diurnal activity (Haim and Izhaki 1995).

In addition, within its natural habitat A. russatus coexists with its congener, A. cahirinus. A. cahirinus are nocturnal and believed to competitively exclude A. russatus (Kronfeld et al. 1994). In a study performed in 1971, when A. cahirinus were removed from an environment, A. russatus became nocturnal (Kronfeld et al. 1994). It was also found that A. russatus body temperatures rise earlier before sunset and drop later than those of A. cahirinus which suggests a physiological adaptation to diurnal activity (Haim and Izhaki 1995).

Communication and Perception

Food Habits

A. russatas are omnivorous and require a relatively moist diet due to high evaporative water loss in the desert. This diet consists mainly of animal matter but also includes snails, insects, seeds, and other plant material (Degen 1994). This particular spiny mouse is diurnal (see behavior) and thus hunts/gathers food throughout the day. In captivity, the golden spiny mouse has been documented eating camel spiders and scorpions. Because food and water are not readily available in the desert, the golden spiny mouse will withstand hunger and thirst for up to nine days (Harrison and Bates 1991). No evidence suggests that spiny mice hunt in teams or packs, however they are social animals and usually live in colonies (see reproduction).

Economic Importance for Humans: Positive

Golden spiny mice are popular pets in parts of the Middle East and can be a food source for pet snakes. Spiny mice are easy to maintain and breed in the laboratory (Nowak 1999). This has led to extensive biological and cancer research with these mice.

Economic Importance for Humans: Negative

In developing arid regions, the golden spiny mouse has become a small nuisance to agricultural fields that use drip irrigation. In particular, A. russatus will eat seeds and destroy certain crops. They sometimes are the focus of public health concern because flea populations on these mice may host Rickettsia, the organism which causes typhus (Nowak 1999).

Conservation Status

Acomys russatus populations are slowly increasing as human progress advances further into deserts and arid regions. This is because human habitation supplies additional food sources for the golden spiny mouse.

Contributors

Benjamin Fishman (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, University of Michigan-Ann Arbor.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

References

Degen, A. 1994. Field Metabolic Rates of Acomys russatus and Acomys cahirinus, and a Comparison With Other Rodents. Israel Journal of Zoology, 40 (2): 127-134.

Grzimek, B. 1990. Grzimek's Encyclopedia of Mammals. New York, NY: McGraw Hill.

Haim, A., I. Izhaki. 1995. Comparative Physiology of Thermoregulation in Rodents: Adaptations to Arid and Mesic Environments. Journal of Arid Environments, 31 (4): 431-440.

Haim, A., F. Rozenfeld. 1998. Spacing Behaviour Between Two Desert Rodents, the Golden Spiny Mouse Acomys russatus and the Bushy-tailed Gerbil Sekeetamys calurus.. Journal of Arid Environments, 39 (4): 593-600.

Harrison, D., P. Bates. 1991. The Mammals of Arabia--second edition. Sevenoaks, Kent, England: Harrison Zoological Museum Publication.

Kronfeld, N., T. Dayan, N. Zisapel, A. Haim. 1994. Coexisting Populations of Acomys Cahirinus and A. Russatus: A Preliminary Report. Israel Journal of Zoology, 40 (2): 177-183.

Nowak, R. 1999. Walker's Mammals of the World. Baltimore, MD: Johns Hopkins University Press.

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