In their new study, Pryke, Roets and Samways discuss how a diverse range of large African herbivore species is essential for the conservation of dung beetles within transformed landscapes, and argue that the maintenance of functional diversity outside protected areas requires the inclusion of large mammals in conservation plans.
Dung beetles need the dung of large mammals to feed and reproduce. In doing so, they grind up dung and bury it, making nutrients accessible for plants and removing a breeding ground for disease vectors. Africa’s iconic megafauna (Elephant, Rhino, Buffalo, Giraffe, etc), on which the dung of many of these dung beetles depend, are increasingly restricted to protected areas. So, how well do dung beetles (and the ecological functions that they provide) survive in transformed landscapes? And how dependent are they on these large mammalian herbivores in these landscapes?
We had the opportunity to sample dung beetles in the Northern KwaZulu-Natal region of South Africa. More specifically, within a timber plantation where a network of large-scale conservation corridors has been established to connect to the iSimangaliso Wetland Park (a world heritage site).
Large herbivores can access the plantations and their corridors. We drove 450 km of transects in the plantation, in the protected area and the road that divides the plantation and protected area. When African elephant, White rhinoceros, Plains zebra, Southern giraffe, African buffalo, Blue wildebeest, Waterbuck, Greater kudu, Nyala, or Bushbuck were spotted, a 2 litre bucket – baited with dung from that specific mammalian species – was laid. In this way we were able to track the dung beetles associated with those specific mammal species.
We laid and collected 386 traps (some others were lost to curious elephants). In total, we observed 2349 mammals, with the most abundant being Wildebeest and Zebra. We collected 26,025 dung beetle individuals from 79 species. Mammals were more abundant in the protected area, but some woodland associated species (Nyala and Bushbuck) preferred to be in the conservation corridors in the transformed areas. Dung beetles showed a stronger association with particular mammal dung (mammals that produce pat were preferred over pellets) rather than level of landscape transformation.
We also constructed Africa’s first mammal to dung beetle interaction network, which showed that protected areas are vital for conserving natural ecological function. They also indicate that the conservation corridors are doing a good job in supporting mammals, dung beetles and their interactions. In fact, a phylogenetically unique dung beetle (Allogymnopleurus splendidus) showed a strong preference for conservation corridors. Interestingly, elephant dung, although not common, was the most important dung type for maintaining local dung beetle diversity.
This means that biodiversity, and specifically functional diversity, can be maintained in conservation corridors within transformed landscapes. The timber plantation that we worked in offers very little to large mammals or dung beetles, but most of these mammals and beetles were found in the corridor areas within the plantations. Thus, a network of conservation corridors consisting of native vegetation is important for conserving biodiversity in production landscapes. It is much more important to dung beetles that native mammals are present, than the level of landscape transformation. This suggests that in studies where dung beetles respond to landscape transformation, they are in fact responding to the removal of indigenous mammal fauna rather than transformation per se.
From this study we can see that maintaining a suite of indigenous mammals is critical to maintaining insect diversity and their functional associations. The loss of any species, and particularly elephants in this system, would likely lead to a decline in dung beetles. This highlights how important Africa’s protected areas are for native biodiversity and they should be protected at all costs with a full complement of native fauna. Outside the protected areas we can retain functional biodiversity, provided we allow native species to move through the landscape. Thus, rather than fencing off wildlife, conservation should focus on alleviating human-wildlife conflict. African conservation managers and landowners should be encouraged to maintain a diversity of large mammals on their properties to preserve functional diversity and ultimately ecological resilience.
Read the full paper Large African herbivore diversity is essential in transformed landscapes for conserving dung beetle diversity in Journal of Applied Ecology