Christopher Buddle
 

Ten reasons to fall in love with dung beetles

13 May 2014 by Christopher Buddle, posted in Insects, Natural History, Ten facts

 

Here's another in the "ten facts" series on Expiscor - this one is written by Rhodes Scholar, Entomologist, PhD Candidate (and all-around great Canadian!) Paul Manning. You can follow Paul's adventures at Oxford on his blog, or follow him on twitter.

Of all the described insects living on Earth, a staggering 40% percent are beetles. With such phenomenal diversity, it's likely that even the most insect-phobic individuals can find a species with a certain amount of appeal. One group with unquestionable charm, are dung beetles. Represented by roughly 7,000 species - dung beetles are a group that has coevolved along with large mammals, depending on a niche resource that most other organisms tend to avoid - dung.

Male Onthophagus imperator. A beautiful beetle from Malaysia, measuring a mere 12mm. Photo by Udo Schmidt

 

Although dung beetles are found throughout the world, many aren't aware of their presence. In Northern temperate climates, dung beetles primarily exhibit endocopry - a behavior which is characterized by beetles living a quiet life within the confines of a dung pat. Beetles found outside of dung, are moving towards a new resource patch (dung pat), looking for any mixture of shelter, food, and mating opportunities. Some other species (paracoprids) dig tunnels below dung pats. These tunnels are then provisioned with dung, which act as cozy safe-havens for developing brood. In tropical climates, rolling beetles (telecoprids) dominate dung resources by quickly relocating it elsewhere before burying, and laying eggs.

If you take the time to examine dung during the warmer periods of the year - you're likely to find these charismatic beetles, you might even fall in love. With rounded scarab features, bumbling movement, and fascinating behavior - how could you not?

In case you're not immediately interested in personally poking through poo, here is a collection of ten interesting features of dung beetles. This will give you an opportunity to fall in love with these amazing creatures from the comfort of your own armchair. But please be forewarned, you might have find yourself having an irresistible urge to visit 'specific habitat patches' at your nearest pasture or woodland.

A healthy looking dung beetle haven. (Photo by Jason Whittaker)

 

1.  Dung beetles improve soil health
Animals defecate. Sharing the world with billions of livestock, and countless other large mammals - there are inordinate amounts of animal waste being produced each and every day. This waste is full of nutrients that can be lost into the atmosphere as ammonia, and washed away into water courses. Dung beetles help close this loop by directly consuming the nutrients as larvae and adults, and through mixing dung into the soil horizon. This keeps the soils healthy, the plants happy, and nutrient cycling more complete.

 

2. Dislike pest flies? Thank a dung beetle for their service.
Arguably the most famous story about dung beetles was a mass exotic introduction into Australia in the 1960-70s. As the cattle market in Australia quickly grew, so did the dung problem. This was welcome news for the Australian bushfly - a vicious biting fly that breeds in dung. Native dung beetles were unable to cope with the sheer amount of wet dung, adapted to process the small, harder waste of marsupials. This left the bushfly with an inordinate amount of dung, providing an equivalent of an 'all you can eat buffet'. Their populations were growing exponentially, until multispecies dung beetle releases by the CSIRO reduced populations to more manageable levels.

 

3. Weird and Wonderful: The fascinating behavior of dung beetles
It doesn't take long to dig up some weird news about dung beetles. Two Ig-Nobel awards were recently awarded to Marcus Byrne, a scientist from South Africa who recently discovered two very odd dung beetle behaviours. The first found that one species of dung beetles navigate by using the Milky Way (this was of course discovered through a process of giving beetles tiny hats). Another found that an odd behavior of a beetle species when rolling a dung ball, was in fact used to reduce heat stress (this finding was found through experimentally giving dung beetles tiny silicon 'boots'). Some dung beetles have become further specialized, such as Zonocopris, a South American monotypic genus that lives and feeds on organic particles + foam of large land snails.

New research from a dung beetle research group in Helsinki, Finland has shown that dung beetles help to reduce methane fluxes from dung pats (Have a look, it's open access)! The study found that fresh dung pats released lower amounts of CH₄ when colonized by a community of small dung-dwelling beetles. Although the study found a curious peak of N₂O, another potent GHG in treatments with dung beetles - it elicits a number of questions in understanding how arthropods influence gas flux from environments.

Aphodius ater, a small endocoprid dung beetle included in the work by Penttilä et al. 2013. Photo by: Udo Schmidt

 

5. Ecological questions can be answered using dung beetles as a model
Dung beetles aren't ideal organisms to study to answer all questions, but given the shared resource they depend on, and the way that is shared, they are ideal study organisms to answer certain questions of community ecology. Much of the well-known and deeply respected work by Ilkka Hanski on meta-population dynamics has focused on dung beetle systems. Dung beetles are sensitive to habitat modifications, and have been often included in studies addressing destruction, and fragmentation of tropical rain forest.

 

6. Ancient cultural significance of dung beetles
Many dung beetles exhibit an interesting behavior during breeding that involves the excavation, of nests provisioned with dung. An Egyptian species Scarabaeus sacer - was an impressive symbol for ancient Egyptians. The beetle forms dung balls from cow pastures in the morning, and then rolls them away. The Egyptians found this strikingly similar to the sun moving across the sky. The burying of the dung, and the emergence of the second generation was thought to be akin to resurrection; a central theme of Egyptian beliefs. It's even been suggested that Osiris God of the Afterlife, is depicted in an inspiration by the pupa shape of S. sacer.

Wall relief with the cartouches of Thutmosis III, Karnak temple of Amun-Ra, Egypt. Photo by: Rémih (Wikimedia Commons)

 

7. Biological Inspiration
The fascinating behaviours of dung beetles, could have wonderful applications for engineering purposes. Take the incredible strength exhibit by large tropical rolling beetles, the design of tarses to claw and dig into the earth. Or the ability of dung beetles to move such enormous masses relative to their size. What sort of endosymbiotic microbial communities allow beetles to live in such biologically unstable conditions? The possibilities are huge!

Brute strength of a dung beetle from Puglia, Italy. Photo by: Gilles St-Martin (Wikimedia Commons)

 

8. Shallow Reasons: Dung beetles are gorgeous
With 7,000 species of dung beetles found globally - there will likely be a few that some find particularly interesting. But as they say, a photo is worth 1,000 words. Here are three simply stunning species.

Geotrupes stercocarius among the largest beetles in the United Kingdom. This species can also be found throughout mainland Europe, and North America. Photo by: Allan Hopkins

 

Aphodius maculatus an endocoprid species found throughout Eastern Europe (photo by U. Schmidt, from Wikipedia commons)

 

9. Pasture grazing is improved by dung beetle activity
Cows are finicky grazers. They don't like to eat in any proximity to where they have previously defecated; can you blame them? This is a problem in pasture systems, as space is often limited. Healthy populations of dung beetles break-down the dung, keeping the pasture from becoming covered, and improving farm productivity. Dung beetles have also been shown to reduce loads of intestinal parasites in cattle through the same mechanism of dung burial and disintegration.

 

10. Dung beetles are a phenomenal gateway to entomology + natural history
Exploring the wonderful world of dung beetles is as easy as the trip to your nearest pasture or forest. Given the relatively small number of species, in most places - you should be able to identify most to morphospecies using free resources available from the internet, or local libraries. As dung beetles are easily to attract, and keep satiated with a bit of dung, they are an ideal group of organism to entertain, inspire, and encourage curious minds.

An Aphodiine dung beetle taking off. Note the phoretic Uropodine mite deutonymph attached to the beetle's elytra. Photo by Gbohne