Saccostomus

Abstract: 1. We measured the simultaneous energy expenditure of five male and six female pouched mice (Saccostomus campestris), over 3 consecutive days, using the doubly labelled water (DLW) technique. The aim was to assess the interindividual scaling of daily energy demands and also the repeatability of measures of daily energy expenditure when using doubly labelled water. 2. Individual mice were housed in cages, given free access to food and water and were kept in a natural photoperiod (February at 26°S) at a mean temperature of 26.5°C (daily range 25-28°C). 3. Males were significantly heavier than the females, as is typical in this species. Mean energy expenditure (Watts) (single-pool model) over 3 days, across individuals, was positively related to body mass (reduced major axis scaling exponent b = 1.96) and to change in body mass over the 3 days

Abstract: The Afrotropical pouched mouse Saccostomus campestris displays sexual disparity in the use of daily torpor; males reluctantly enter torpor. We tested the hypothesis that males may compensate for a limited heterothermic capacity with lower basal and resting metabolic rates relative to females. We also investigated the association between gonadal activity (testosterone) and the propensity for daily torpor. Body temperature and oxygen consumption were measured at various ambient temperatures and were compared between sexes under ad libitum and restricted-diet treatments. Whereas no significant sex differences were observed in body temperature and oxygen consumption under ad libitum treatment, there were pronounced differences in heterothermic responses under food restriction. Females employed torpor more frequently and also had lower minimum torpor body temperatures (ca. 25°C) than males (ca. 29°C). Testosterone inhibited torpor in males, whereas the majority of saline-treated animals employed torpor under both ad libitum and restricted-diet treatments. This study demonstrated that the limited capacity of male S. campestris to enter torpor is a consequence of reproductive activity and that opportunistic breeding and the absence of seasonal testes regression compromises the capacity to conserve energy through daily torpor.

Abstract: The feeding habits of seven rodent, and an elephant shrew species from the semi-arid Karoo, South Africa were determined by microscopic examination of stomach contents. The elephant shrew Macroscelides proboscideus was found to consume significant amounts of vegetation, making it a functional herbivore/ insectivore. Two of the rodents (Otomys unisulcatus and Parotomys brantsii) formed a herbivorous guild, while the remainder (Gerbillurus paeba, Mus minutoides, Rhabdomys pumilio, Desmodillus auricularis and Saccostomus campestris) were omnivorous. The paucity of granivorous small mammals in the Karoo contrasts the patterns of trophic specialization for North American and Israeli semi-arid communities, but is similar to that of South American and Australian semi-arid communities.

Abstract: Mastomys natalensis, Aethomys chrysophilus and Saccostomus campestris are three common and widespread rodent species in the Kruger National Park. Chromosomal and protein electrophoretic investigations reveal that these species are in fact complexes of morphologically similar, though genetically distinct, species. Their respective distributions in the Kruger National Park are reported and species diagnostic characters (diploid chromosome number, genitalia, spermatozoa and electromorphs) are presented for the practical identification of the cryptic species. The value of a genetical approach to resolving cryptic species is emphasized with respect to ecological studies.