Habitat, food, and small mammal community structure in Namaqualand

M Van Deventer,J.A.J Nel

doi:10.4102/koedoe.v49i1.103

Abstract

The effect of habitat differences and food availability on small mammal (rodent and elephant shrew) species richness, diversity, density and biomass was investigated in Namaqualand, South Africa. Species richness in the three habitats sampled, namely Upland Succulent Karoo, Dry Riverine Shrub and North-western Mountain Renosterveld was low, with only 2–4 species per habitat. Rodents trapped were predominantly Gerbillurus paeba and Aethomys namaquensis, with fewer Mus minutoides and Petromyscus sp. The only non-rodent was the elephant shrew Elephantulus edwardii. Ten habitat features, the percentage of total plant cover, tree cover, shrub cover, grass cover, plant litter, total basal cover, sand, gravel or rock cover, and the dominant plant height were recorded at 30 randomly chosen points on five sampling grids in each habitat. Small mammal density and biomass was significantly correlated with food availability (green foliage cover, seeds, and relative density and biomass of insects). Species richness and diversity of small mammals were significantly correlated with shrub cover. Numbers and biomass of specific species correlated significantly with different habitat features in each case.

Highlights

Small mammals, especially rodents, are often abundant, widely distributed and important components of most terrestrial ecosystems, especially in semi-arid or arid areas (Brown et al 1986; Price & Jenkins 1986; Kerley & Erasmus 1992)
G. paeba occurred in all three habitats; A. namaquensis and E. edwardii in Upland Succulent Karoo and North-western Mountain Renosterveld, while Petromyscus sp. and Mus indutus were only recorded in the Upland Succulent Karoo and Dry Riverine Shrub habitats respectively
Our study recorded fewer species than others in Namaqualand and other arid or semi-arid parts of South Africa (Dieckman 1979; Nel 1983; Kerley & Erasmus 1992; Joubert & Ryan 1999), and far fewer than the diverse small mammal fauna of North American deserts (Brown & Lieberman 1973), but not that of the Argentinian Monte Desert (Mares 1976). This could be due to previous disturbance brought about by intensive smallstock grazing before the park was promulgated (Avenant 2000), or trapping during a trough in small mammal density resulting from the preceding extensive drought

Summary

Introduction

Especially rodents, are often abundant, widely distributed and important components of most terrestrial ecosystems, especially in semi-arid or arid areas (Brown et al 1986; Price & Jenkins 1986; Kerley & Erasmus 1992). Especially rodents, may be reliable indicator species because they are abundant enough to allow meaningful statistical analysis of data, belong to different trophic levels and functional guilds, and are studied (Brown 1975). Their community characteristics can reflect ecological disturbance in, e.g., conservation areas (Avenant 2000).

Methods

Results

Conclusion