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.

Ecophysiological Studies Research Group, School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg, South Africa.
Journal of Comparative Psychology (Impact Factor: 1.89). 04/2004; 118(1):37-47. DOI: 10.1037/0735-7036.118.1.37
Source: PubMed

ABSTRACT The authors studied the striped mouse (Rhabdomys pumilio) in the semiarid succulent karoo of South Africa. Mice forage alone, but they live in groups that share a common nest. Groups consist of 1 to 4 breeding females, 1 to 2 breeding males, and their offspring of both sexes, which remain in their natal group even after reaching adulthood, participating in territorial defense and nest building without showing signs of reproductive activity. Interactions are typically amicable and take place inside or in front of the nest. In contrast, encounters with mice from other groups are aggressive. Group living in the succulent karoo is possibly due to ecological constraints imposed by habitat saturation because of a year-round stable food supply as well as associated benefits of philopatry.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Abstract Early separation from a family is stressful for young mammals, but might be more stressful for group-living than solitary species. Using juvenile males of three African striped mice Rhabdomys taxa that are either group (R. pumilio) or solitary (R. dilectus dilectus and R. d. chakae) living, we predicted greater separation anxiety in R. pumilio than R. dilectus because group-living could reduce anxiety in R. pumilio. Three brothers from each of 10 litters per taxon were randomly assigned soon after natural weaning (25 days) to one of three treatments for 10 days: 1) remained with the family (philopatric); 2) separated from the family by a wire mesh barrier (separated); and 3) isolated from the family (isolated). Males were individually tested in a four-arm maze to assess their anxiety responses and sampled for corticosterone concentrations 20 mins and 10 days later. Compared to R. dilectus males, R. pumilio males showed a greater treatment response to separation: philopatric males used the light arms of the maze less and had higher corticosterone concentrations compared to isolated males, which spent the most time in the light arms and had the lowest corticosterone concentrations overall; separated males showed an intermediate behavioural response, but had similar corticosterone concentrations to philopatric males. Thus, separation from a family group is more stressful in group-living Rhabdomys and this stress response dissipates with time. Philopatry and group-living may be more important for young R. pumilio, whereas dispersal at weaning is an important life history event for solitary R. dilectus.
    Stress (Amsterdam, Netherlands) 04/2014; · 3.21 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Arginine vasopressin (AVP) is an important hormone for osmoregulation, while as a neuropeptide in the brain it plays an important role in the regulation of social behaviors. Dry habitats are often the home of obligately sociable species such as meerkats and Damaraland mole-rats, leading to the hypothesis that high plasma AVP levels needed for osmoregulation might be associated with the regulation of social behavior. We tested this in a facultative sociable species, the African striped mouse (Rhabdomys pumilio). During the moist breeding season, both solitary- and group-living reproductive tactics occur in this species, which is obligatory sociable in the dry season. We collected 196 plasma samples from striped mice following different reproductive tactics both during the moist and the dry season. Solitary mice did not have lower AVP levels than sociable mice, rejecting the hypothesis that peripheral AVP is involved in the regulation of alternative reproductive tactics. However, we found significantly higher AVP levels during the dry season, with AVP levels correlated with the abundance of food plants, the main source of water for striped mice. Plasma AVP levels were not correlated with testosterone or corticosterone levels. Our study underlines the important role that AVP plays in osmoregulation, particularly for a free ranging mammal living under harsh arid conditions.
    General and Comparative Endocrinology 05/2014; · 2.82 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: An individual's home range determines its access to resources, significantly influencing its fitness. Food availability and population density are considered to be among the primary factors influencing home range sizes; however, no study has experimentally tested whether these two factors affect home range sizes independently. This is important as these two factors correlate significantly with each other, making it difficult to differentiate the effect of one from the other. First, we supplemented food to 23 female African striped mice, Rhabdomys pumilio, belonging to 15 different groups. To avoid an increase in population density by immigration, we also provided food to neighbouring groups. Although population density did not increase, female home range sizes decreased by 43.1%. In a second experiment, we manipulated population density by removing entire social groups of striped mice. We carried out experiments within 7 weeks, a period short enough to control for a change in natural food availability. Experimental decrease of population density caused an increase of female home range sizes of 44.3%. The degree of home range overlap between female striped mice was unaffected by supplemental feeding or by reduction of population density. However, female home range sizes were negatively affected by the total number of female neighbours, especially of heavier individuals. In addition, after removal, females significantly decreased their overlap with neighbouring breeding females indicating that competition with same-sex individuals shapes females' home ranges. This is the first comprehensive experimental field study demonstrating that an increase in food availability and a decrease in population density independently affect home range sizes of individuals. © 2014 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.
    Animal Behaviour. 11/2014;

Full-text (2 Sources)

Available from
May 22, 2014