An endless stream of white butterflies.
February was that time of the year again when an apparently endless stream of white butterflies decorated our skies. Every year, early to mid-summer, millions of Brown-veined Whites (Belenois aurota) head northeast. Its Afrikaans name, Witgatwitjie, is rather quirky. This en masse dispersal event starts in the Kalahari and projects as far as the Mozambique Channel and perhaps beyond. It is proposed to relieve overcrowding, especially after a good rainy season. As with many butterfly species, larvae of B. aurota are hard-wired to only eat leaves from very specific plants. Since larvae can easily defoliate a tree, the pressure to find adequate larval food supplies is at the core of their yearly dispersal. It was particularly pleasing to watch waves of B. aurota move purposefully across the Haenertsburg Nature Reserve.
The reserve sits right next to Haenertsburg village and is home to a magnificent collection of different plant species in what is known as the largest intact remnant of critically endangered Woodbush Granite Grassland (WGG). About 630 different plant species have been identified in WGG. As one can imagine, the assortment of flowers is like a lavish food platter for butterflies. In stark contrast to B. aurota, that has a conservation status of least concern, are two permanent inhabitants of WGG that are classified as critically endangered. Consider yourself really lucky if you ever get to see a Wolkberg Zulu (Alaena margaritacea) or a Wolkberg Copper (Aloeides stevensoni). Both species occur in extremely restricted colonies on steep grassy slopes in the Wolkberg wilderness area. Their very specific habitat requirements and their dependence on WGG, which in itself is critically endangered, make them particularly vulnerable to extinction. Only two populations of Wolkberg Zulu, and one population of Wolkberg Copper butterflies have ever been discovered. Agricultural activity, afforestation, inappropriate veldt fires and especially infestations by invasive plant species are at the top of the list of major threats to their survival.
Friends of the Haenertsburg Grasslands (FroHG) has been custodians of the remaining sections of WGG since 2007. At the end of last year, FroHG commissioned André Coetzer and colleagues, from the Lepidopterists’ Society of Africa to conduct a butterfly survey in the Haenertsburg Nature Reserve, with funding provided by Rotary Haenertsburg. The survey took place 19-21 December, as this is the time of the year when chances of finding the Wolkberg Copper-and the Wolkberg Zulu butterflies are at its peak. To date there hasn’t been a butterfly survey to establish the exact number of butterfly species present in the WGG. It has however been suggested that more than 50 butterfly species, including 4 endangered species, is expected to inhabit the WGG.
Unfortunately, the weather had other plans and most of the days were cold and wet. A thorough assessment will have to take place at a later date this year. For those of us who are curious to know which butterfly species inhabit the nature reserve, we will simply have to hold our breaths. There is at least some good news. Even though the survey team ended up looking at butterfly food plants, they were able to confirm that the Wolkberg Zulu is still present in the Wolkberg area!
FroHG is a registered nonprofit organization (209-267 NPO) and relies on support from its members, sponsors and the public to carry out its mission of conserving one of South Africa’s most threatened ecosystems. Please consider donating today.
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