19 Sep Oh Poo!
By Dr Jean Holley, UNE Discovery Voyager
In our UNE Discovery Voyager activity Plants, Poop and Pollinators, we play a role-playing game where students become busy dung beetles, rolling away balls of manure and ‘burying’ them in their underground dung beetle nests. The dung beetles (students) must roll away as many balls of manure (rubber balls) as they can, using only their dung beetley legs (croquet mallets). Whichever dung beetle pair has the most dung balls in their nest at the end of the game are the winners. This is a great game that explores themes such as nutrient cycling, competition, reproduction and sneaky alternative strategies for resource acquisition.
In the dung beetle game, we discover the life histories of teleocoprid, or roller dung beetles. But rolling away balls of manure is not the only way that dung beetles can stow this precious resource. More on that in a moment. Firstly, you may ask what do dung beetles do with the manure in the first place? The simple answer is that they eat it, and use it to breed in. Adult dung beetles feed on the liquid component of manure, while the larvae eat the dung solids. Yum! Adult dung beetles also use manure to construct broods for their young, with the young developing inside these broods.
Broadly speaking, dung beetle species can be divided into three main groups based on how they use manure. Paracoprid, also known as tunneller dung beetles, bury manure directly under a dung pat. These beetles create tunnels under a pat, and take manure down into these tunnels, packing it into lumps called broods. Females will lay their eggs inside these broods, and depending on the species, there can be one or multiple eggs laid inside these lumps of dung. Teleocoprid, or roller dung beetles, form a ball of manure, roll this away from a dung pat, and then usually bury the ball. An egg will be laid inside the ball, and the larvae will develop and feed on the manure inside. When we play the dung beetle game in our Plants, Poop and Pollinators activity, our student dung beetles belong to this group. The third group, the endocoprids or dwellers, brood their larvae directly inside a dung pat. In addition to these three groups, a fourth group, the kleptocoprids, deserve mention. These sneaky beetles breed in the dung buried by other beetles, or stealdung balls made by others.
After a larva hatches inside its brood, it will feed on the stored dung in the brood, growing through three stages, or ‘instars.’ The third instar will turn into a pupa, and then an adult. The adult will emerge from the soil, and fly, or walk to fresh dung. The adults will feed for some time, before starting to breed. Through their feeding and breeding, dung beetles provide many economically and ecologically important benefits to agriculture and natural systems. The activity of dung beetles removes dung from pastures, promotes nutrient cycling, increases water penetration and aeration of the soil, and secondarily disperses seeds in animal manure. Beetle activity in dung pats can also destroy the breeding sites of fly pests and reduce the free-living stages of gastrointestinal parasites of livestock.
Not only do these charming little beetles provide such crucial benefits to agriculture and natural systems, I think it’s just marvellous that something has evolved to make use of the waste of something else. What nifty little beetles!
References and further reading:
Doube, B, and Marshall, T. 2014. Dung Down Under: Dung Beetles for Australia. Dung Beetle Solutions Australia. Bridgewater, South Australia.
Edwards, PB, Wilson, P, and Wright, J. 2015. Introduced Dung Beetles in Australia: A Pocket Field Guide, 3rd edn. CSIRO Publishing, Clayton, Australia.
Holley, JM, and Andrew, NR. 2019. Experimental warming disrupts reproduction and dung burial by a ball-rolling dung beetle. Ecological Entomology 44: 206–216.