| Summary: | Exxaro KZN Sands is planning the development of a heavy minerals strip mine south of Mtunzini, KwaZulu-Natal, South Africa. The degree to which mining activities will affect local herpetofauna is poorly understood and baseline herpetofaunal diversity data are sparse. This study uses several methods to better understand the distribution and abundance of herpetofauna in the area. I reviewed the literature for the grid squares 2831DC and 2831 DD and surveyed for herpetofauna at the study site using several methods. I estimate that 41 amphibian and 51 reptile species occur in these grid squares. Of these species, 19 amphibian and 39 reptile species were confirmed for the study area. In all, 29 new unique, grid square records were collected.
The paucity of ecological data for cryptic fauna such as herpetofauna is particularly evident for taxa that are difficult to sample. Because fossorial herpetofauna spend most of their time below the ground surface, their ecology and biology are poorly understood and warrant further investigation. I sampled fossorial herpetofauna using two excavation techniques. Sites were selected randomly from the study area which was expected to host high fossorial herpetofaunal diversity and abundance. A total of 218.6 m3 of soil from 311 m2 (approximately 360 metric tons) was excavated and screened for herpetofauna. Only seven specimens from three species were collected. All were within approximately 100 mm of the surface even though some samples removed soil 1 m below the surface. There was no detectable difference in fossorial herpetofaunal density (individuals.m-2) between methods or from areas under different land uses. Neither soil compaction nor land use nor soil texture predicted fossorial herpetofaunal density or abundance. The data suggest that fossorial herpetofauna occur at extremely low densities in the area. This finding has implications for population estimates and conservation measures for these species.
In order to better understand the effects of land use on herpetofaunal diversity, I used sample-based rarefaction curves to compare the diversity of the herpetofaunal species assemblages occurring in each of the four main land uses on the study site. Forest areas hosted significantly higher diversity than grasslands and the two agricultural mono-cultures, Eucalyptus and sugarcane plantations. Additionally I demonstrated empirically that riparian woodlands host higher species richness and herpetofaunal abundance than non-riparian areas. Potential reasons for the apparently suppressed diversity of these areas include the use of pesticides and/or herbicides, harvesting regimes, and the
reduction in habitat heterogeneity. The potential value of riparian woodlands as refugia and corridors that could facilitate recolonisation of revegetated areas post-mining is discussed.
Negative influences of mining activities on local herpetofauna are of particular interest given the potential and verified presence of several threatened taxa in the area including Bitis gabonica, Python natalensis, Afrixalus spinifrons, Hemisus guttatus and Hyperolius pickersgilli. These, as well as the “conservation needy” species proposed in a specialist report on the impacts of the mine on local herpetofauna are discussed in the light of my fieldwork. Mitigatory measures are required to reduce the negative impacts likely to be experienced by certain threatened taxa. I discuss a proposal for the development of a wetland reserve targeting, among other amphibian species, H. pickersgilli.
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