Poo believers: dung beetles get ready to graduate

By  Ian Dewar 24 May 2024 5 min read

Our dung beetle research is part of a long legacy. It's still making a difference on farms around Australia to this day. 

Native dung beetles can't deal with the larger, wetter dung of livestock like cows and sheep. That’s where our introduced species can step in and get the dung ball rolling.

Now the class of 2024 is about to graduate from lab to field.

We caught up with our proud dung beetle parents, to find out what it’s been like to work with this much-loved species.

Graduating top of the grass

Over the past five years, we imported three new dung beetle species. These included two tunnellers (Onthophagus vacca and Onthophagus andalusicus) and one roller (Gymnopleurus sturmi).

Rollers and tunnellers deal with dung in different ways. The tunnellers bury dung underground from where it lands. The rollers break bits of dung off, shape them into balls and roll them away to bury them.

Both types of beetles use the dung as a food supply for adults and larvae. They lay their eggs in buried balls of dung.

Entomologist Dr Valerie Caron hadn’t worked on dung beetles before coming to us.

“I fell in love with them quite quickly because they're so cute and they have these little quirks,” Valerie said.

“It’s hard not to love them because they're so interesting.”

“What surprised me was how much I needed to know about dung. It’s really an entire ecosystem in itself,” she said.

Dung is very low in nutrients. Dung beetles process it using a specialised gut microbiome. The bacteria in their stomach help them break down the cellulose in the dung and access all the amino acids they need to grow.

The specialised gut microbiome is passed down from the mother – unless something gets in the way. Cue our importation and quarantine process. It involves sterilising the eggs’ surface and disrupts the transmission of the microbiome to young beetles.

“We end up hatching smaller beetles, because they don’t get that head-start,” she said.

“We’d like to study this more and eventually make a special microbiome that we can inoculate them with,” Valerie said.

Dung love

Research technician Patrick Gleeson has been working with our dung beetles for over 10 years. And he’s spent a lot of that time cleaning up cow poo.

“My supervisor told me many years later that I was the only person interviewed for the role who was prepared to work with cow poo!” Pat said.

 "Earlier programs imported sanitised dung beetle eggs. When I was starting, we switched to bringing in adult beetles via secure quarantine as a better way of doing things."

Once in Australia, the original adults aren’t brought out of quarantine – but their eggs are cleaned and released from our quarantine centre.

Releasing eggs from quarantine is a delicate operation, especially when the eggs come enclosed in a special baby beetle brood ball. This ball of dung protects a single egg and provides the food source for the larvae.

Our scientists take the eggs out of the brood balls in quarantine. They sterilise the surface following approved procedures. They then heat treat the empty brood balls to sterilise them, before taking them out of quarantine and putting the eggs back inside.

This worked well for the two first species. But the third and final species didn’t respond well to this treatment.

So instead, the team put the eggs into new, handmade brood balls once they’d passed through quarantine.

“We pressed and kneaded the dung to get a similar sort of moisture content to what would be in a natural brood ball and put the eggs inside,” Pat said.

“Because this dung didn’t need to be heat treated, it still had most of the bacteria and good things in natural dung that the beetles need.”

The baby beetles from these bespoke brood balls came out a lot bigger.

Hatching a plan

Pat said that they had to tweak the temperatures to get a good rate of egg production. By adding a period of cooler temperatures, they could stop them hatching too fast. This ensured they could collect all the eggs from quarantine.

As well as being sensitive to temperature, it turns out dung beetles are quite fussy eaters. They prefer dung with the right texture, high protein and good moisture content.

“Spring dung, from actively growing grasses and herbs, is the best quality and their preferred option,” Pat said.

“So, we ended up collecting it, freezing it and storing it in a shipping container as our ultimate dung diner,” he said.

There are still gaps in dung beetle activity in Australia – both between seasons and across different locations. Valerie has a wishlist of further species to research. She wants to see those gaps filled with more targeted species. 

Our researchers are also thinking about how to clean up dung from feral animals. Bush flies breed wherever there is dung, including in places where feral animals produce a lot of it. So, introducing some new dung beetle in the future could help clean up those areas, and keep flies under control. 

What impressed Valerie most was the legacy that came with this project.

“It’s been pretty amazing to be part of it,” Valerie said.

“For me it’s always important to see my work can make a difference, and I can see how dung beetles make a big difference for farmers and the environment.”

“Everyone loves dung beetles,” Pat said.

“They’re one of our most popular insects – and they’ve got the gross factor with the poo so kids love them!”

They say it takes a village to raise a child, and that is certainly true for dung beetles! A large team of dedicated people helped raise these beetles. Now they're ready to leave the nest.