It’s all about what you do with the doodoo! (Dung Beetles)

This week we look into all the dirty details on Dung beetles including how they saved Australia! 

 

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Transcript: 

 

Welcome back to episode 48 of Insects for Fun! Technically there are 49 episodes but I didn’t count for some reason a long time ago and I’m just sticking with it, the same way today’s insect sticks itself to dung! Today is a listener request from Donna wanting to learn more about Dung beetles! 

Intro: 

 

It turns out there are a ton of Dung beetles, so much so that they are divided into four different categories and spread out through multiple families of beetles. They all belong to one superfamily though, called Scarabaeoidea which houses around 35,000 species of beetles with a couple hundred being added every year. And yes dung beetles are actually scarab beetles and are depicted in Ancient Egyptian hieroglyphs but we’ll talk more about that later.

 

The four types of dung beetles are: rollers, tunnelers, dwellers, and stealers, and as you can probably guess it has everything to do with how they use dung. 

 

Roller’s are probably the most well known out of the dung beetles and these ones are your stereotypical dung ball rolling beetles. In scientific literature many people refer to them as telecoprids which derives from the words tele as in distance, like a telephone and then coprid which comes from the genus of true dung beetles known as copris. These beetles can roll dung balls up to 50 times their own size and are willing to go the distance, to find a suitable place to bury it and use it for food or eggs. 

 

Tunnelers bury the dung where it was found, and are referred to as endocoprids with endo meaning within. These beetles set up camp underneath dung patties, and will pull dung from the surface down into their holes where they’ll use it as a food source and place to lay eggs. 

 

Dwellers don’t move the dung at all. They just live in it wherever it is found, and are referred to as paracoprids with the prefix para meaning near or alongside. These dung beetles run the highest risk of getting trampled or eaten by another animal. 

 

Stealers are as you can imagine the thieves in all of this, and they aren’t doing it for justice. These dung beetles are referred to as kleptocoprids with the prefix klepto meaning impulse to steal with no real reason. These beetles wait out for opportune moments to steal dung balls from other rollers, and use it for their own gain. They’re evil nature is even found in the larvae which actually kill other larvae that were already in the dung ball. 

 

As you can tell each type of dung beetle is not limited to a specific genera or family because all the beetles above come from the copris genus 

 

That being said, most dung beetles have a similar shape and that would be a very compact, round and hard looking body with a much smaller head. They come in many sizes though with some being as large as 7cm and the smallest being as small as 3.4mm. Fun fact: The strongest insect is a dung beetle scientifically called Onthophagus taurus, and can pull dung up to 1,114 times its own weight. That’s like having a person pulling 6 double decker buses… 

Life Cycle, and food source: 

 

The life cycle of a dung beetle begins like most beetles going through complete metamorphosis starting as an egg and then going through a larval and pupal stage before emerging as an adult. The only major difference is that dung beetles rely exclusively on Dung to do it. 

 

The true dung beetles within the subfamily scarabaeinae feed on dung only while other dung beetles may actually feed on other decaying matter or even fruits and mushrooms. But all dung beetles use poo for the completion of their life cycles by laying eggs in it and having their larvae develop off of it. The truth is dung beetles can get everything they need in terms of nutrients and even hydration from dung which is kind of insane to think about. This is actually why if dung gets too hard and dry it becomes unusable to beetles. In places like Africa for example the rainy season increases dung beetle populations. 

 

It should also be stated that not all dung is equal and certain species of dung beetles prefer veggie patties over omnivore or beef patties, and! They even go as far as to prefer dung from specific animals. For example in Australia almost all of the 500 species of native dung beetles prefer marsupial poo and won’t touch cow patties or dung produced by other mammals. This actually caused a big problem when cattle were introduced into Australia in 1788. One cow can produce up to 12 cow patties in a day, now imagine thousands of cows, millions of cows, and having their dung just sit on the ground not going anywhere. This was not only a big eyesore, but it was breeding millions and millions of bush and buffalo flies which both feed on mammals for nourishment causing sores and irritation. Eventually a Hungarian entomologist named George came to Australia and proposed introducing dung beetles from other places like Hawaii and Africa which are well versed in cleaning up cow patties. The project started in 1965 and ran until 1985 introducing hundreds of thousands of dung beetles from 4 species. Today at least two of the four species still remain active in Australia and the number of bush flies dropped by 90 percent. (wow)

 

There are actually 29 species of introduced dung beetles currently in Australia which are all helping keep the bush flies and buffalo flies down as well as keeping the land fertile. 

Behaviors: 

 

Earlier we talked about behaviors differentiating each of the four kinds of dung beetles, so now I want to go into some more specialized behaviors. For example dung rollers in Africa have evolved a behavior of sitting on their dung ball and wetting their front legs with a regurgitated liquid to cool themselves down when the sands reach temperatures over 50C. This behavior is repeated more and more with elevated temperatures. 

 

Another cool behavior seen in ball rollers specifically is something called an orientation dance. The beetles will often stand atop their dung balls and do a “dance” but to me it looks more like a ground survey, turning around and looking at their surrounding before hopping off and rolling their load, and turns out this is in fact what its for. They are also known to do this sort of surveying when the ground isn’t flat because bumpy roads can easily derail the direction of a ball and dung beetles like to roll their dung balls in a straight line away from the source so as to not end up in crowded areas.

 

Why avoid the crowds? Well, dung beetles like other beetles have a habit of fighting each other, and it's much safer to avoid other beetles than risk losing your dung ball. In fact rollers actually don’t usually have horns or any large exterior weaponry because it slows them down and makes it more difficult to get away. Rollers want to get the goods and get out as soon as possible. 

 

Now continuing on the topic of navigation there is one very special dung beetle in Africa which is known to use the Milky Way! This beetle scientifically known as Scarabaeus satyrus is able to navigate even on moonless nights by orienting itself along a straight path using the milky way as a guide. It doesn’t rely on other stars or even the moon, and studies have repeatedly shown that this beetle can do it under a variety of conditions. That being said, if the sky is cloudy or there is a lot of light pollution then the beetle gets lost and can’t accurately navigate at night. 

 

Tunnelers on the other hand don’t have any navigational problems, but they do have the struggles of one on one combat, which is often why these beetles do have horns. Even the females of some species are armed with horns because they have to fight too, but for precious resources. This arms race of who has the better horns can lead to some crafty sneak tactics. A classic case of brawn versus brain comes into play with tunneler species in the genus Onthophagus which we mentioned earlier as having the strongest insect.  Males of this genus are often horned and have to fight off invading males who want to mate with a female, but some of these males have evolved to look more like females and they can sneakily enter the females den by making a backdoor while the horned males are on guard or in a battle. It was actually found that the sneaky males have greater testes than those of the horned males, because less genetic resources were placed into making a large clumsy horn.

 

Rollers and Tunnelers often form pairs when it comes to breeding. Rollers will give a dung ball to a female if he sees one and if she accepts then they both will roll it away together to start a den. Tunnelers on the other hand don’t have to travel and males will search out a female's den, and either stake it as their own or sneak in through a back door. 

Defenses and Predators: 

 

Dung beetles are often preyed upon by other larger animals like birds, mammals, reptiles and even other insects sometimes, but they don’t usually have any special techniques for saving themselves. In general their go to defense is to run away or hide, but to be fair living in or smelling like dung is already a pretty solid defence. 

 

Lore: 

 

Now let’s get back into the whole scarab beetle thing, which is to say that dung beetles belong to the scarab beetle family, and they have been viewed with great power by ancient egyptians. In fact one species called scarabaeus sacer was viewed as a sacred beetle and is found in many paintings. The image is linked to the meaning of transformation and has strong ties to the god of the sun known as Khepri. These beetles are often depicted as carrying the sun, and were believed to spawn from nothing.  

 

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