Why should we care about dung beetles?
Dung beetles provide valuable ecological and economic services. The net value of dung beetles is estimated at ~$2 billion per year for the agriculture and cattle industries worldwide. As nutrient recyclers, dung beetles aid in dung decomposition while integrating the natural fertilizer in the soil. They provide important ecosystem services, such as secondary seed dispersal, control of other insects or parasite suppression, dung and nutrient recycling in ecosystems and subsequent increasing of soil permeability and fertility. In healthy natural grassland ecosystems, dung beetles can be hyper-abundant, with a record number of almost 12,000 specimens extracted from 1.5 kg of elephant dung in Kruger National Park, South Africa. Their presence helps maintain ecological sustainability by increasing plant biomass in a way that manual labour could not reasonably achieve.
In healthy veld conditions, dung beetles will scatter a dung pile in very short time (Figures 1–2). In the dry season, when the insects are dormant, the dung is often left untouched. This can become an indicator of dry or wet season droppings when assessing the history of an area. Unbroken buffalo and other droppings sitting for years on the soil surface are an indicator of serious soil problems and bad veld conditions. Like all animals, the beetles require moisture, air and food. Without one of these they will perish. Their presence or absence is a valuable veld condition indicator, apart from being an interesting attraction.
Can dung beetles battle global climate change?
It may seem like an unlikely environmental hero. But the dung beetle, with its sordid habit of laying eggs in and eating cow poo, might just be a weapon in the battle against global warming.
Farming activity is a gassy business. The 1.3 billion large ruminants—dairy cows and beef cattle, buffalo, sheep, goats—that burp, fart, and poop around the world emit more greenhouse gases than does the transportation industry, according to the UN. These animals are responsible for about a third of global emissions of methane, a gas that makes up half of farming’s contribution and is even more potent than the much-maligned CO2.
Dung beetles, by the way, dig burrows into pasture faeces and feed on the droppings of cows and other ruminants. They also deposit their eggs in the excrement, and their hatchlings feed on the same stuff. A study in Finland found that cow patties with beetles, specifically Aphodius species, rummaging around in them released nearly 40 percent less methane over a summer period than beetle-free cowpats did.
Are dung beetles in danger?
The use of antiparasitic drugs used for preventing and treating intestinal worm infections in livestock (e.g., ivermectin) has proven to be especially harmful to dung beetles. When excreted with faeces, high doses of such helminthicides can be fatal for dung beetle populations, while low doses cause sensory and locomotor disorders in dung beetles. Livestock diet also plays a role: dung from cattle fed with supplements of grain contains fewer and smaller dung beetle offspring than dung from pasture-fed livestock. Recently, behavioural changes in dung beetles have been reported in dung from pigs fed with genetically modified Bt maize. In overall dung beetles are no exception in being challenged in the Anthropocene.
Hanski, I. and Cambefort, Y. eds. (1991). Dung Beetle Ecology (Princeton: Princeton University Press). Holter, P. (2016). Herbivore dung as food for dung beetles: elementary coprology for entomologists. Ecol. Ent. 41, 367–377.
Krell, F. T., and Moon, A. R. (2019). Dung beetles. Current Biology, 29(12), R554-R555.
Nichols, E., Spector, S., Louzada, J., Larsen, T., Amezquita, S., Favila, M.E., and The Scarabaeinae Research Network. (2008). Ecological functions and ecosystem services provided by Scarabaeinae dung beetles. Biol. Conserv. 141, 1461–1472.
Scholtz, C.H., Davis, A.L.V., and Kryger, U. (2009). Evolutionary Biology and Conservation of Dung Beetles (Sofia and Moscow: Pensoft).
Simmons, L.W., and Ridsdill-Smith, T.J. (2011). Ecology and Evolution of Dung Beetles (Chichester: Wiley-Blackwell)
Slade, E.M., Riutta, T., Roslin, T., and Tuomisto, H.L. (2016). The role of dung beetles in reducing greenhouse gas emissions from cattle farming. Sci. Rep. 6, 18140.
Figure 1. Dung beetles rolling dung balls in uMkhuze Game Reserve, Kwazulu-Natal, South Africa
Figure 2. Dung beetles decomposing cattle dung pats in uMkhuze Game Reserve, KwaZulu-Natal, South Africa