Influence of variations in land use intensity on species diversity and abundance of small mammals in the Nama Karoo, Namibia

The influence of the intensity of land use on small mammals in the ecoregion Nama Karoo, Namibia was investigated within the biodiversity programme BIOTA. Changes in species diversity and abundance were investigated across a fence separating heavily grazed communal and lightly grazed government owned rangeland. Assessing and monitoring of the small mammal populations were done seasonally from 2001-2003 on each of 2ha plots by using capture-mark-recapture methods. In total, 311 individuals representing nine species were caught within 5760 trap nights. Species richness, total abundance, species diversity and settlement was lower in the overgrazed area. The most abundant species were the Gerbillinae, Gerbillurus vallinus and Tatera leucogaster. T leucogaster did not occur in the overgrazed area. Due to the loss of grass cover, smaller bush diversity, bush encroachment and smaller arthropod abundance in the overgrazed area, changes in the small mammal community were most likely caused by the loss of food resources, available dew, disruption of habitat structures, cover and shelter and by increased predation risk. Only the `desert' species, G vallinus, was favoured by the degraded land. It is also obvious that the uncontrolled grazing in the communal lands has affected the biodiversity and the regeneration potential, thus leading to land degradation.