Although I was vaguely aware of dung beetles and their role in the ecosystem, I finally became interested in them while participating in giraffe research in South Africa. I’ll never forget the time when I was finishing up my giraffe work for the day and I stopped to watch a couple of dung beetles who were squabbling over a single ball of dung (poop). What I had perceived to be a relatively gentle disagreement escalated quickly when I watched one demolish the other with a long-time favourite move from the World Wrestling Foundation, the Brainbuster. You know the one.
Dung beetles play an essential role in the environment. However, they fly a bit under the radar, which is why they are often called nature’s “unsung heroes.” There are over 100 species of dung beetle, each choosing one of three strategies: rolling, tunneling, or dwelling in dung. Not only do they eat and live in animal dung, but they increase the freak by reproducing in it and burying it. This ensures their offspring have plenty of food for when they hatch.
As gross as it is, this burying behavior strongly limits the growth of vertebrate parasites, which is tremendously helpful to the rest of the ecosystem. They help remove animal dung from the surface environment with incredible efficiency and speed. In some places, the beetles can eliminate a pile of dung in less than 10 minutes, where the ground would otherwise be carpeted with it.
Dung beetles are very widespread, found in many different habitats across all continents except Antarctica. Like many species, dung beetles appear to be harmed by the break-up of natural environments. This fragmentation reduces the size of undisturbed, or core, habitat in the centre and creates isolated habitat patches. The environment along the edge of a habitat is usually quite different from the core. In forests, for example, it’s typically windier and sunnier at the edge of the forest than in the centre.
Edges are not only susceptible to environmental challenges, but also to human impacts. They are more vulnerable to fire, as well as illegal harvesting or collecting of plants or animals by humans, simply because they are more easily accessible. Some of these impacts along the edges don’t stay localized, but can radiate into the core habitat as well.
Edges are in fact an important habitat, because they support species that like transitions between different habitats. However, as humans continue to break up large habitats, with roads or communities for example, the amount of edge habitat increases, while core habitat shrinks. This challenges the animals that rely on core habitat. Additionally, the edges of habitats typically support fewer species than the core. We don’t want to consistently change habitats around the world to ones that support similar and fewer species.
Buffer zones are areas around a sensitive, often legally protected, environment that are typically managed to reduce edge impacts on the borders of a sensitive area. Sometimes buffer zones have methods to exclude humans or livestock, such as fences. Sometimes they are simply designated areas without active protection measures. Relatively little is understood about how effective buffer zones actually are for some species.
Back to dung beetles, we typically see fewer individuals and a less diverse group of dung beetles along habitat edges than in the core, because they are a group that tends to be quite affected by human activities. For example, because they are in constant contact with dung, they are exposed to pesticides that livestock ingest, which has been causing population declines. But how do buffer zones impact dung beetle diversity and density along the edge of protected habitats?
Andrew Barnes and his colleagues, including the late Rowan Emberson from Lincoln University, decided to find out. The montane rainforests in Sub-Saharan Africa are shrinking rapidly, largely due to deforestation for agriculture and grazing. There is also nearby habitat decline that often comes with agriculture. The Ngel Nyaki forest reserve in Nigeria is a heavily fragmented area. To test how dung beetles would respond to increasing edge effects, the researchers applied experimental habitat restoration treatments to certain areas along the edges. For the restoration, researchers excluded livestock with fencing, created and maintained firebreaks to help block fire, and allowed passive natural regrowth of the floral community. This combined restoration occurred in 200 metre buffer zones over the course of three years.
The impact of these buffer zones was remarkable. In the forest next to the restoration area, the dung beetle population size increased by over 50% compared to the unrestored areas. Perhaps more important was the difference between dung beetle populations in the edge and habitats. Before the restoration, there were many more species of dung beetles in the habitat core and relatively few in the edge. After the restoration, that difference disappeared, meaning that the buffer zones successfully mitigated the challenges that are typical of edges for dung beetles. The restoration also led to the return of certain species that had previously locally disappeared in the degraded habitat.
These changes are incredibly pronounced and occurred after only three years and with small levels of restoration. While firebreaks do require active maintenance, it is encouraging that even relatively minor land-use changes around protected areas can make a world of difference for many species. Relatively few studies have been completed about the effectiveness of buffer zones, so this is a single, but vital, drop in a much larger pot of conservation decisions.
After all, we want all dung beetle species to survive, no matter how gross or freaky, to tidy up after vertebrates and perhaps to get more inspiration for wrestling moves.
This article was prepared by Master of International Nature Conservation student Julia Criscuolo as part of the ECOL608 Research Methods in Ecology course.
Barnes, A.D., Emberson, R.M., Chapman, H.M., Krell, F-T., & Didham, R.K. (2014). Matrix habitat restoration alters dung beetle species responses across tropical forest edges. Biological Conservation, 170: 28-37. DOI: http://dx.doi.org/10.1016/j.biocon.2013.12.006
