Rhabdomys

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Rhabdomys Fossil range: Late Pliocene to Recent
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Rodentia Family: Muridae Subfamily: Murinae Genus: Rhabdomys Thomas, 1916
Species
Rhabdomys dilectus Rhabdomys pumilio

Rhabdomys is a small (40-50g) muroid rodent that is widespread and abundant in the southern African subregion (De Graaff, 1981; Willan & Meester, 1989; Pillay, 2000a, b, c; Skinner & Chimimba, 2005; Schradin & Pillay, 2005). Unlike most rodents, the Striped mouse exhibits a diurnal, bimodal activity pattern, with activity concentrated around mornings and evenings, and reduced during the midday period (Perrin, 1981; Schumann et al., 2005). Its omnivorous diet, its ability to survive without water provided its food has a minimum water content of 15% (Willan, 1982), and its extreme plasticity in habitat preference are likely reasons for its wide (if discontinuous; Brooks, 1982) distribution throughout southern Africa (Rambau et al., 2003).

Contents 1 Breeding 2 Social structure 3 Morphology 4 Karyotypic forms 5 References

[edit] Breeding

Rhabdomys is a seasonal breeder and reproductively active from spring to autumn (Willan & Meester, 1989; Schradin & Pillay, 2003). After a gestation period of 22-23 days, free-living females give birth to approximately five pups; captive females have slightly larger litters (e.g. 7.2 ±1.8; Pillay, 2000). Pups begin to consume solid food at ten days, leave the nest from twelve days, and weaning occurs at around 16 days. Sexual maturity is reached at approximately five to six weeks (range 34 – 90 days; Brooks, 1982). Timing of sexual maturity, as well as dispersal age, depends on environmental factors (e.g. resource availability), social cues (e.g. the presence of older, reproductively active animals), as well as the animal’s developmental history (e.g. weight at weaning; sex-ratio of litter; Mason & Latham, 2004). Females have an inter-litter interval of approximately 23-30 days (Pillay, 2000).

[edit] Social structure

Rhabdomys has a flexible social organisation and mating system that appears to be shaped primarily by resource (particularly food and cover) availability and, secondarily, by population density. In arid habitats (e.g. Namib; Krug, 2002; Kalahari; Nel, 1975; Nel & Rautenbach, 1975; Succulent karoo; Schradin & Pillay, 2005a, b) Rhabdomys can be described as a territorial, group-living, solitary forager that displays biparental care (Schradin & Pillay, 2004). In mesic, grassland habitats (e.g. Kwa-Zulu Natal Midlands; Wirminghaus & Perrin, 1993; Pretoria Highveld; Brooks, 1974; Zimbabwe grassland; Choate, 1972) and semi-succulent thorny scrub (e.g. Eastern Cape; Perrin, 1980a, b) animals are solitary, with females rearing their litters on their own, and both sexes maintain territories that overlap the territories of the opposite, but not the same, sex (Schradin & Pillay, 2005a). However, males from both mesic and xeric populations display parental care in captivity (Schradin & Pillay, 2005b), suggesting a plesiomorphic occurrence in the mesic populations, since the desert-living form represents the ancestral form (Rambau et al., 2003).

[edit] Morphology

There is some regional variation in morphology. Striped mice from the southwestern regions of southern Africa are slightly larger than animals from the more northern regions, and animals from the xeric western areas have a paler coat than do mice from the mesic, eastern regions (Pillay, 2000a, c). In addition, there appear to be population level differences in personality – an animal’s characteristic and consistent style of behaviour (Reif & Lesch, 2003) – and stress-sensitivity (suggested by Reuther, 2000), although these differences have yet to be investigated empirically.

[edit] Karyotypic forms

Two karyotypic forms of Rhabdomys (2n = 28 and 2n = 46) have been detected. Based on this finding and on the analysis of mitochondrial DNA, as well as evidence of divergent behavioural repertoires among populations (e.g. courtship behaviours; Pillay, 2000b; Pillay et al., 2006). Rambau et al. (2003) suggest that R. pumilio be reclassified as two species: R. pumilio (the social form that occurs in xeric habitats; 2n = 48) and R. dilectus (the solitary form, found in mesic areas, that comprises two subspecies R. d. dilectus, 2n = 46, and R. d. chakae, 2n = 48).

[edit] References

• Brooks, P. M. 1974. Thesis, University of Pretoria.
• Brooks, P. M. 1982. Aspects of the reproduction, growth and development of the 4-striped field-mouse, Rhabdomys pumilio (Sparrman, 1784). Mammalia, 46:53-63.
• Choate, 1972
• De Graaff, G. 1981. Rodents of South Africa.
• Krug, 2002
• Mason & Latham, 2004
• Nel, 1975
• Nel & Rautenbach, 1975
• Perrin, 1980a
• Perrin, 1980b
• Perrin, 1981
• Pillay, N. 2000. Female mate preference and reproductive isolation in populations of the striped mouse Rhabdomys pumilio. Behaviour, 137:1431-1441.
• Pillay, N. 2000a. Fostering in the African striped mouse: implications for kin recognition and dominance. Acta Theriologica, 45:193-200.
• Pillay, N. 2000b. Reproductive isolation in three populations of the striped mouse Rhabdomys pumilio (Rodentia, Muridae): interpopulation breeding studies. Mammalia, 64:461-470.
• Pillay, 2000c
• Pillay, N., J. Eborall, and G. Ganem. 2006. Divergence of mate recognition in the African striped mouse (Rhabdomys). Behavioral Ecology, 17:757-764.
• Rambau, R. V., R. Stanyon, and T. J. Robinson. 2003. Molecular genetics of Rhabdomys pumilio subspecies boundaries: mtDNA phylogeography and karyotypic analysis by fluorescence in situ hybridization. Molecular Phylogenetics and Evolution, 28:564-575.
• Reif & Lesch, 2003
• Reuther, 2000
• Schradin, C. and N. Pillay. 2003. Paternal care in the social and diurnal striped mouse (Rhabdomys pumilio): Laboratory and field evidence. Journal of Comparative Psychology, 117:317-324.
• Schradin, C. and N. Pillay. 2004. The striped mouse (Rhabdomys pumilio) from the succulent karoo, South Africa: A territorial group-living solitary forager with communal breeding and helpers at the nest. Journal of Comparative Psychology, 118:37-47.
• Schradin, C. and N. Pillay. 2005. Demography of the striped mouse (Rhabdomys pumilio) in the succulent karoo. Mammalian Biology, 70:84-92.
• Schradin, C. and N. Pillay. 2005a. Intraspecific variation in the spatial and social organization of the African striped mouse. Journal of Mammalogy, 86:99-107.
• Schraden, C. and N. Pillay. 2005b. The influence of the father on offspring development in the striped mouse. Behavioral Ecology, 16:450-455.
• Schumann, D. M., H. M. Cooper, M. D. Hofmeyr, and N. C. Bennett. 2005. Circadian rhythm of locomotor activity in the four-striped field mouse, Rhabdomys pumilio: A diurnal African rodent. Physiology and Behavior, 85:231-239.
• Skinner & Chimimba, 2005
• Willan, 1982
• Willan, K. and J. Meester. 1989. Food deprivation and drinking in 2 African rodents, Mastomys natalensis and Phabdomys pumilio. South African Journal of Zoology, 22:190-194.
• Wirminghaus, J. O. and M. R. Perrin. 1993. Seasonal changes in density, demography, and body composition of small mammals in a southern temperate forest. Journal of Zoology, 229:303-318.
• Homepage Succulent Karoo Research Station in Goegap Nature Reserve ]