The population biology and socio-spatial organisation of the woodland dormouse, Graphiurus murinus (Desmarest, 1822), was investigated in a riverine forest at the Great Fish River Reserve (GFRR), South Africa. Data were collected by means of a monthly live trapping and nestbox monitoring programme. Between February 2006 and June 2007, 75 woodland dormice were trapped and/or found in nestboxes and marked: these were 39 adults (13 males, 21 females, five undetermined) and 36 juveniles (five males, 14 females, 17 undetermined). The population showed a steady increase from June 2006–November 2006 and a peak in December 2006–January 2007 as a result of the influx of juveniles. The minimum number of dormice known to be alive (MNA) varied between 40 in December 2006– January 2007 (summer), and a low of three in June 2007 (winter). The range in population density was therefore between 1.2 and 16 dormice per ha. Winter mortality and/or spring dispersal accounted for the disappearance of 55 percent of juveniles. The overall annual adult:juvenile ratio was 1.08. The overall sex ratio was 1.94 female per one male. In females, reproductive activity was observed from September 2006 to end January 2007. The pattern observed in males was similar, as dormice with descended testes were exclusively found from October to end January. Females gave birth during the second half of October to beginning of February. Litters (n = 11) consisted of an average (± SD) 3.73 ± 0.47 young. Over the study period, 27 dormice were trapped or found in nestboxes more than eight times, thus allowing me to estimate their home range size and the spatial overlap between these individuals. On average, dormouse home range size was 2,514 m2 (range: 319 – 4,863 m2). No difference was recorded between one-year old adults and older adults, or between all adults and juveniles. However, adult male dormice (3,989 m2, n = 5) had home ranges almost twice as large as females (2,091 m2, n = 9). No similar trend was found in juveniles. Intrasexual home range overlap was on average 62 percent in adult males, and 26 percent in adult females. However, females overlapped with more neighbouring female home ranges than did males with neighbouring male home ranges, so that, as for males, only small parts of female home ranges were really exclusive. On average, males overlapped a larger Abstract Ecology of woodland dormice M.Sc. Thesis 16 proportion (48 percent) of female home ranges than did females with neighbouring male home ranges (27 percent). In addition, males overlapped with significantly more female home ranges (7.8) than did females with male home ranges (4.9). Trapping success and nestbox data agree with the socio-ecological model. Females showed increased mobility during summer, more likely to find suitable nesting sites, and food for milk production during the reproductive season. The use of nestboxes, however, was constant throughout the year. In males, both the trapping success and nestbox use were higher during the mating season (spring), when an increased mobility and occupation of nestboxes probably increased the chances to locate and mate with (a) receptive female(s). Hence, food and (artificial) nest sites may constitute an important resource for females, whereas females seem to represent the main resource for males. Although food availability was not determined, a comparison of female and male distribution patterns provided interesting information on the mating system of woodland dormice. In GFRR, the dispersion pattern of female woodland dormice was “rather” clumped, i.e. females were non-territorial. As some females showed a dyadic intrasexual overlap of up to 90 percent, and population density was very high at the study site, this may indicate that food was very abundant and/or renewed rapidly. Based on the wide range of birth dates observed during the study period, females clearly come into oestrus at different times. In such circumstances (asynchronous sexual receptivity in females), the Female in Space and Time Hypothesis (Ims 1987a) predicts that males will be non-territorial and promiscuous. Live-trapping, nestbox use and home range data indeed suggested that male woodland dormice do not defend territories, but search for and aggregate around receptive females during the mating season.