Guild structure and population dynamics of small mammal assemblages in suburban patches of KwaZulu-Natal Sandstone Sourveld grassland within eThekwini

Abstract

The KwaZulu-Natal Sandstone Sourveld (KZNSS) landscape is one of the Critically Endangered ecosystems that forms part of the Maputaland-Pondoland-Albany (MPA) biodiversity hotspot. It is a biodiversity hotspot which supports important assemblages of endemic fauna and flora and provides social and ecological services to the eThekwini assemblages. More than ~90% of this landscape has been completely altered and modified, and only ~0.1% is under statutory protection. To understand and improve conservation efforts for this threatened ecosystem, it’s important to understand the effects of anthropogenic and environmental factors on biodiversity in this vegetation type. The Durban Metropolitan Open Space System (D’MOSS) initiative is one of the eThekwini efforts to conserve areas with high biodiversity value. Small mammals are key components in terrestrial ecosystems and their abundance and diversity are key bioindicators of ecosystem health, habitat quality, and the impacts of fragmentation. This study aimed to assess small mammal guild structure, species richness, diversity and population dynamics between D’MOSS and protected areas within this landscape. A Capture Mark Recapture (CMR) approach was used to monitor the seasonal dynamics of the native small mammal assemblages. Live trapping transects and H.B. Sherman™ live box traps were implemented inside and outside three protected areas (Krantzkloof Nature reserve, Giba Gorge Nature Reserve and Doornrug and Uitkomst Conservancy (reference site)) between July 2018 and June 2019. Over 16 586 trap nights, 890 unique individuals representing 11 small mammal species from 8 families and two Orders, were captured. The haul was dominated by rodent species. Mastomys natalensis (54%) and Rhabdomys dilectus (28%) suggesting that these species form the core of the small mammal assemblage in this threatened landscape. Local elevational gradients, regional variation and habitat management regimes (treatments) had a significant influence on total captures, trap success, minimum know alive (MKA), species richness and diversity Slope aspect, one of the under-surveyed environmental variables in small mammal studies significantly influenced total captures, trap success, MKA, and species richness, while seasonal variation significantly influenced total captures and MKA. Grassland condition significantly influenced total captures, MKA, and species richness. The body size of several small mammal species varied in response to changes in elevational gradients, slope aspect, seasonal variation, grassland