English colonists who brought cattle to Australia in 1788 soon faced the problem of foul smell. The piles of dung that slowly and tastefully disappeared back home were not going anywhere. Instead, they continued to grow larger, and became infested with blood-sucking flies that infested the cattle.
It took nearly two centuries for the explanation to emerge: Australian dung beetles, which were more accustomed to marsupial dung than cattle, left the deposits where they lay. The Australian cattle industry only realized the benefits when the European dung beetle was introduced into the country in 1968.
Stories like these testify to the important services dung beetles provide. The most iconic of these insects collect the excretory material into a ball, roll it up, and then bury it underground. Others create tunnels under the feces and collect it without even noticing. Some simply dig holes in a dung heap and create a den within it, where they feast. All of these activities can provide economic value to farmers, although how much has long been unclear. In a recent paper in the journal Basic and Applied Ecology, ecologist Roisin Stanbrook-Byrd of Bethune-Cookman University in Florida attempted to calculate an accurate figure.
He worked with a team of colleagues to study cattle feces on two farms and a state park in south-central Florida and found that when dung beetles were present, the feces in a representative pile averaged 10.7 grams per day. Disappeared at the rate of. In contrast, when beetles were absent, feces disappeared at a rate of 3.7 grams per day.
This inequality has consequences. Studies have shown that cattle avoid feeding in an area six times larger than the dung footprint. Firstly, foul smell is responsible. However, once the odor subsides, the nutrients in the feces cause the grass to quickly mature and become tasteless. Over time, this can lead to large areas of pasture being unused and ultimately affect how quickly cattle get fat. Dr. Stanbrook-Bayer found that dung beetles counteract these negative effects. They estimate that ensuring a healthy presence of beetles on all farms in Florida would increase statewide revenues by more than $1m per year.
This figure may seem small, especially compared to the millions of dollars that pollinating insects provide the state each year, but it may be an underestimate. Dr. Stanbrook-Bayer says, among other things, dung beetles prevent the spread of parasites in cow populations, help cycle nutrients in the soil and improve water quality by keeping feces out of streams. Are. Studies conducted in other parts of the world suggest that the total benefits provided by beetles to livestock farmers would be in the millions.
However, the real value of these insects goes beyond simply increasing beef production. Dung beetles are locked in an evolutionary battle with fungi for access to their favorite food. To gain an edge and keep the dung fungus-free, they prepare it with a mixture of their feces and saliva. To find out how this mixture works, Mario Favila at the Institute of Ecology in Xalapa, Mexico, collected gut bacteria from three dung-beetle species and cultured these microbes in the laboratory.
Working with a team of colleagues, he exposed them to nine strains of pathogenic fungi that cause serious problems in agriculture. The team reports in Nature that microbes found in two of the dung-beetle species were very effective at inhibiting the growth of seven fungi. Microbes from a third species, Onthophagus batesii, significantly reduced the growth of all nine. With pathogenic fungi becoming more resistant to existing anti-fungals, dung beetles have never looked more attractive.
