Namaqua Dwarf Adders (Bitis schneideri) are small viperids that inhabit sandy coastal habitats within the Succulent Karoo Biome in southern Africa. Their ecology, and the faunal ecology within the region in general, is poorly documented, hampering effective conservation planning for this biodiversity hotspot. We used radio telemetry to investigate the spatial ecology of a population of B. schneideri. We measured mean daily displacement (MDD) of 19 male and 18 female snakes during the austral spring, summer, and winter. We also compared mean squared displacement from center of activity range (MSD), a measure of home range area, for males and females between the three seasons. Finally, we compared MDD of another 60 individuals collected using mark–recapture techniques. In general, snakes did not move great distances. Males moved further during spring (47.3 ± 3.9 m.day−1) than during summer (3.3 ± 4.5 m.day−1) or winter (3.0 ± 5.0 m.day−1). Female MDD did not vary significantly across spring (6.4 ± 4.6 m.day−1), summer (2.7 ± 3.7 m.day−1), or winter (0.8 ± 6.5 m.day−1), nor was it different from the MDD of males during summer and winter. MDD in the mark–recapture group did not differ among adult males, adult females, or juveniles. Home range area estimates varied between sexes and within seasons, generally corresponding to patterns shown for MDD. Overall mean home range size was larger in males (0.85 ± 0.09 ha) than females (0.10 ± 0.09 ha). Our data suggest that gene flow in Bitis schneideri is likely to be facilitated through the movement of male snakes during spring. However, the relatively short distances over which males range (even the most mobile males are sedentary compared to other species), and the apparent lack of any significant dispersal in juveniles, implies that the species may be vulnerable to fragmentation at relatively fine spatial scales. Thus, conservation management of the Succulent Karoo, the biome to which the species is restricted, should be aimed at minimizing habitat fragmentation.
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Vol. 2012 • No. 1