A pat on the back for dung beetles

Published 21 March 2018

Dung beetles are very picky creatures. This surprising fact has emerged as part of new knowledge being generated at the University of New England (UNE) about one of the few insects that has garnered universal human respect.

To a dung beetle, not all dung is equal. According to University of New England (UNE) researcher Amrit Pal Kaur, the right dung has to be a certain consistency and smell good – and these qualities are dependent on the time that has passed since the dung was excreted.

“I’ve found that fresh poo juice (or poo-ju) contains a varying abundance of different smells from one-hour poo-ju, and three-hour poo-ju is totally different again,” said Amrit, an insect ecologist and PhD candidate. “It’s the quality of these volatiles – and I’ve identified over 110 different chemical compounds – that influence where and when dung beetles feed.”

Amrit is part of a team of researchers who, over the past five years, have made UNE a national centre for dung beetle research. They are putting science behind why an insect venerated by the ancient Egyptians still has a valuable role to play in the agricultural and environmental challenges of the 21st Century.

Amrit’s investigation into what tantalises a dung beetle’s tastebuds (or antennae) is part of a broader effort at UNE to breed and multiply dung beetles independent of seasonal cycles, so that land managers can have year-round access to these industrious nutrient recyclers.

“In the winter, when their preferred food is more scarce, dung beetles generally become dormant,” said Amrit. “I’m trying to replicate the high-quality summer dung they like, which is nutritious and rich in nitrogen, and of the right consistency and moisture content for tunnelling and making broods. If we can do that, then we might be able to help farmers to multiply their beetle numbers and guarantee their presence year-round.”

Dung beetles dine exclusively on dung. After extracting its nutrients, they use remaining particles to make up to 23 balls (called broods) per kilogram of dung, into which they lay their eggs. These broods are made underground, and a single beetle can bury 200 times its body weight in a single night. In the process, the dung beetle decomposes the dung and controls fly populations, improves soil fertility and possibly even sequesters carbon.

But all of this hinges on beetles being attracted to dung in the first place, and they appear highly selective. Not just any old dung will do.

“I have done so many trials, using all sorts of substances to devise artificial diets for beetles,” Amrit says. “I have five or six different poo-ju recipes that I am currently refining, but I am still trying to get the moisture levels and consistency right. It’s quite a challenge.”

But the pay-off could be huge. Dung beetles – both our native species and those introduced to Australia from 1968 – are conservatively estimated to be worth about $800 million annually to Australian agriculture. Just what ecosystem services they provide is the subject of another project that UNE researchers are about to embark on, to dig further into dung beetle biology and ecology.

“We already know that they reduce the impact of bush flies and livestock worms, thereby making cattle more healthy and farmers happier,” said Associate Professor of Entomology at UNE, Nigel Andrew. “Dung beetles also increase the value of farms, by making more fodder available and recycling nutrients back into the soil. But we need to understand more about what they do in the Australian context, and how our 500 native species interact with the 23 introduced dung beetle species.”

This latest project draws on considerable dung beetle expertise developed at UNE. For more than five years, UNE researchers have been conducting population surveys, studying how dung beetles mitigate greenhouse gas emissions, and working to educate farmers about the environmental benefits they bring.

“We’ve become something of a national centre for dung beetle research, with projects underway from coastal areas to Coonabarabran, on introduced and native species, on farmland and in national parks,” said Nigel.

“Once you start understanding their basic biology and how dung beetles function, you can potentially start to solve a range of agricultural and biological problems. For instance, some species can move the dung 20-25 centimetres into the soil, and that’s where carbon can be stored for long periods of time. If we can get dung beetles moving the carbon into that area, there are some interesting interactions and potential carbon sequestration implications for land managers.”

As far as study subjects go, dung beetles are also pretty neat.

“They are one of the few animals universally admired by people in rural and regional areas,” Nigel said. “They are very charismatic , don’t sting and help to ensure we have fewer flies, so we can comfortably enjoy barbecues outside in the summer. And slowly they are giving up their secrets, one dung pat at a time.”