[1] Univ Witwatersrand, Sch Anim Plant & Environm Sci, ZA-2050 Johannesburg, South Africa
[2] South African Environm Observat Network SAEON, ZA-0001 Pretoria, South Africa
[3] Univ Pretoria, Dept Geog Geoinformat & Meteorol, ZA-0028 Pretoria, South Africa
[4] Univ Cape Town, Dept Biol Sci, ZA-7700 Rondebosch, South Africa