I have run across many interesting things over my career, but none more so than Dung Beetles. My interest in pastureland ecology has grown over the years, and the way all of the species of plants and animals interact in the pasture is one of the most fascinating and poorly appreciated processes on earth.
We take many things we take for granted, or don’t even recognize due to our busy lives that are preoccupied with the grand challenges of life. As a child, I was especially interested in insects. Like many children I had an “ant farm” where I could observe an ant colony in my own bedroom. My ant farm came to a crashing end when I took it to the elementary school “hobby show” and dropped it on the concrete floor! My teachers talked about the ant infestation I caused for years to come.
If I had discovered dung beetles at that early age it might have sent me into a totally different direction with my career. As it turned out, specializing in beef cattle nutrition and grazing management allowed me to participate in interdisciplinary teams that included experts in soil health, veterinary entomology, forage agronomy, water quality, etc. All these important aspects of pastureland ecology should be considered in management plans because they are integrated into the system we know.
My colleague Wes Watson first got me interested in Dung Beetles in the 1990s. I had seen them on nature shows, almost exclusively the “roller” type that make a ball of manure and roll it across the pasture to be buried. These shows were typically filmed on the savannahs of Africa, and I never realized that dung beetles are actually found all over the planet, wherever there are animals and their associated piles of poop. My dad once met a field scientist in Alaska that had spent his entire career studying dung beetles specialized to use bear feces!
Once we started talking about Dung Beetles with Wes, I showed my ignorance and indicated that I didn’t think we had any on our farm. After he showed me how to look for them, I went home and found they were everywhere I looked. I can’t believe they were there all that time and I never knew it. As our conversations continued, we decided to study them more deeply.
Wes recruited a graduate student, Matt Bertone, to work on improving our understanding of dung beetles in our region. Matt did trapping studies in the Piedmont and Coastal Plain of North Carolina, and also did work to show how manure nutrients were transported from the cow pie down into the soil profile. Matt went on to become Dr. Bertone, and he currently runs our Plant Disease and insect clinic.
Through this work I started learning more about Dung Beetle ecology. There are three major categories of Dung Beetles including: 1) Tunnelers, 2) Dwellers, and 3) Rollers. Tunnelers burrow under the cow pie for several days where they create brood chambers, which they then pack with manure and eggs. The tunnels may be up to 18 inches deep and are critical to the aeration and water infiltration capability of the soil. The Dwellers stay in the cow pie most of the time and lay their eggs either in the cow pie or in the soil immediately underneath. A large population of dwellers can literally shred a cow pie or pile of horse manure in less than 24 hours winning them their other common name “shredders”. Finally, the Rollers make a ball of manure which they roll away from the cow pie before burying it with their eggs.
Dung Beetles are very beneficial because they increase soil aeration, improve water infiltration, destroy fly and worm habitat, and incorporate manure nutrients deep in the soil. An added benefit shown in recent research at NCSU is that they actually reduce the production of greenhouse gasses associated with the breakdown of feces and urine in the soil.
In Matt Bertone’s trapping studies, we identified 28 species in the Coastal Plain and 14 species in the central Piedmont. At all locations, the vast majority of beetles we found were of the tunneler
“Onthophagus taurus”. The dweller “Labarus pseudolividus” was the second most common. About 70% of the total beetles trapped were O. taurus and 15% were L. pseudolividus. This is consistent with my observations since that time; we see many species but it seems that the most common and abundant are these two. They both emerge in March and are active through November when the fly season is underway. Both of these species were unintentionally introduced from Europe and have now spread across much of the USA. Onthophagus taurus was first found in the US in Florida in 1971. Since that time it has spread over a wide geographic region.
Of course there are also many other insects that are attracted to fresh cow pies; many of them are important in dung breakdown like the beetles, and some of them are pests including face and horn flies. An active population of dung beetles and other dung-dependent insects can reduce fly populations through competition for food resources and destruction of the habitat needed for fly larvae development.
We recently did a series of eight “Amazing Grazing” workshops across the state of North Carolina. At each of these we discussed dung beetles and participants were able to see large numbers, especially O. taurus and L. pseudolividus. We also had a few Digitonthophagus gazella, Phanaeus vindex, Parataenius simulator, and Sphaeridium scarabaeoide to show. We discussed some fun facts about dung beetles including how they were revered by the ancient Egyptians, how they were introduced into Australia, Hawaii and other places where cattle had been imported but there were no dung beetles to degrade their manure, and how Onthophagus taurus is widely considered to be the earth’s strongest animal pound for pound.
We had many questions about how to increase dung beetle populations. It is possible to purchase dung beetles at the current time, but they are expensive and the legality of commercially moving insects across state lines without regulatory approval is questionable. The truth is that if your farm is good dung beetle habitat they are probably already there.
The first step in getting more dung beetles is to go to the pasture and look for dung beetles to make sure you don’t already have a lot. The best time to do this is when it is warm and moist in early summer. Look for fresh cow pies that have holes in the top and look to be flattened and uneven on the surface. Slip a flat shovel under the cow pie, wait 30 seconds and then turn it over. Dung beetles will have dug down to the surface of the shovel and will be obvious. You can also dunk the cow pie into a bucket of water and stir it up. Gradually dung beetles will float to the surface and can be easily skimmed off.
If you disturb a cow pie and it appears that it has dead dung beetles in it, just wait a few seconds. Their normal behavior is to play dead to fool birds, and after a short time of being still, they will pop back to life and rapidly dig into the cow pie!
If you really don’t have any dung beetles then it might be due to things you are doing to your cattle. All things are connected, and research has shown that compounds like ivermectin and other pesticides do reduce populations at least for a short time. If you infrequently use these inputs, they might not cause problems, but aggressive treatment for internal and external parasites undoubtedly reduces populations of some of these species.
To reduce the impact, reduce the frequency at which you use them pesticides and don’t treat all animals at the same time. Unfortunately, it is probably true that the most effective internal and external parasite control programs probably also reduce dung beetle populations. Reserving these treatments for situations where they are really needed most will help. For example, deworming only young cattle but not mature cows can help keep worm populations under control while reducing impact on dung beetles.
Using less toxic compounds whenever you can will also help. An example of this would be to use a “white” dewormer (which is less persistent in manure) rather than an invermectin type which will remain in manure for up to a month. Also, using these compounds late in the season after most of the dung beetle activity slows down can also help. Don’t destroy their habitat if you can avoid it. We have known many cattlemen that drag pastures to scatter manure. This is recommended after winter feeding when there are many stacked up cow pies, but during the grazing season let the biology do it’s work.
Fly control products in the mineral is also something to think about. Methoprene (active ingredient in Altosid) is thought to only have a small impact on dung beetles while diflubenzeron (active ingredient in ClariFly) is thought to have a greater impact.
Products with a very long residual period need to be carefully considered. Once there were ivermectin slow release boluses that payed out the compound all grazing season. These worked great on worms, but did lead to severe decreases in dung beetle populations. Those boluses are no longer on the market in the USA, but there are other “long acting” ivermectin family products that undoubtedly have the same impact. Using products known to impact dung beetles can have less effect if used outside of the March to October active time for the most abundant species.
Finally, recent research shows that toxic Kentucky-31 tall fescue results in a reduction in dung beetle breeding success compared to feces from cattle grazing novel endophyte tall fescue. Both O. taurus and D. gazella were less successful in Ky-31 feces, and when given a choice they preferred feces from cows fed novel endophyte tall fescue. This is yet another place that the toxins in KY-31 tall fescue play a destructive role in pastureland ecology. Conversion of KY-31 pastures into non-toxic forages would be very beneficial not only to the cattle, but also to the other biology at play in your pastures.
Dung beetles are just one more reason to get interested in the ecology of your pastures. Once you find them and start thinking about how to improve your populations, you will be on the way to improving your pastures in general!
For more on dung beetles go to our Amazing Grazing Resource page at; https://go.ncsu.edu/amazinggrazingresources
~ Matt Poore. Originally written for the Carolina Cattle Connection Amazing Grazing Column.
The Alliance for Grassland Renewal is a national organization focused on enhancing the appropriate adoption of novel endophyte tall fescue technology through education, incentives, self-regulation and promotion. For more resources or to learn more about the Alliance for Grassland Renewal, go to www.grasslandrenewal.org
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