Finsbury Dung Beetles

DUNG BEETLES OF FINSBURY

I got a message from Ian Keogan from Finsbury House (unit 23) recently, asking for me to feature Dung Beetles in my next blog. Well, I checked my list of beetles for the estate and found that I had quite a bit on the interesting little creatures. So I thought that it would be a good idea to oblige, especially since they have also always fascinated me as well.

Dung beetles belong to the largest order of insects, the beetles, Coleoptera, with almost 400 000 species so far described. They are typical beetles and are grouped mainly in the family Scarabidae but also in the Geotrupidae. Morphologically, they are typical scarabs like the Fruit Chafers featured in my previous blog but what makes them different is their adaption to eating the exrcement, almost exclusively, of larger mammals. The larvae are regarded as vegetarians because they eat the undigested, dry vegetable matter found in mainly herbivore droppings. The adults not so much because they eat the liquid portion of fresh herbivore droppings which consists of a soup of the living and dead microorganisms used by the herbivore, in it's gut, to help digest vegetable matter.

Dung beetles detect their food mostly by smell, although sometimes they just hang around a herd of animals and wait for them to evacuate their bowels. Their smell is well developed as anyone who has enjoyed a "boskak" (not sure what else to call it so I will resort to army talk) in the game rich areas of our beautiful country will attest to. It is most awkward to watch and hear the beetles arrive from downwind, en masse, and promptly begin work while one is still squatting! This quick response, by the beetles, is necessary because of the intense intra and interspecific competition between dung beetles on a single pile of excrement. This is easy to observe on a fresh elephant dropping in the lowveld at the right time of the year where literally thousands of individuals of a bunch of species can be found. Because of this competition, species have split into groups that handle the situation differently:

The telecoprids are the most noticeable to us because they are ones that arrive at the scene and quickly cut a chunk off the pile of excrement and form it into a ball and hastily roll it away from the area. A good example, although I have not seen one here on the estate, is the Large Copper dung beetle, Kheper nigroaeneus, pictured above, that I photographed in the Lowveld recently. Although they have evolved the behaviour of rolling balls away to avoid competition with other species, they often arrive at large mammal excrement piles in such numbers that it can be quite a sport to watch them frantically rolling balls and defending them against others who try to steal them. They flip their opponent over onto their backs and while the opponent attempts to right himself, they try to roll the ball as far away as possible to avoid further confrontation. This goes on until the winner manages to sneak off with the ball.

An, as yet unidentified, species breaking up the droppings of a large male Warthog in the Whisky valley near W9.

In amongst all this mayhem, this busy time is also the time for males and females to find each other and form bonds. Initially, male and female telecoprids roll a ball away until they find a suitable spot to bury it. Once buried, they eat it together and mate. This ball is called the Nuptial Ball, and eating it together is very much like getting married. Once mated, they will attend another pile of excrement, roll a ball and bury it at the bottom of a relatively deep hole where the female will deposit a single egg in it. They will repeat this process until the hole is filled with 3 to 4 balls, each with an egg laid within.

 The larva, a fat white grub, hatches within this secure environment and eats the ball out from the inside, leaving the hard, dried muddy covering intact. The larva then pupates within the ball and digs it's way out when it emerges. Interestingly, the larva whose egg was laid last into the top ball in the pile in the hole is the one who hatches and pupates first so when the adults emerge from the balls below, they don't experience too much traffic trying to bypass the others above.

One thing I remember when walking through the bush was how often I found how these balls had been dug up by Honey Badgers who had extracted the grub or pupa as a tasty morsel. The Honey Badgers seemed to have an uncanny ability to find this buried treasure!

The paracoprids arrive at the scene and immediately burrow a hole beneath or beside the pile of excrement in which they retreat while they deal with the stuff. A good example of a paracoprid is the above Rhinoceros Beetle, Heliocopris atherstoni, a hornless female. Once they have dug a hole beneath or beside the pile of excrement, they stuff the chamber with excrement, periodically laying an egg. The female beetle remains in the chamber with the offspring to protect them, particularly from parasitic insects, until they emerge as adults. A very rare example of parental care amongst insects.

The endocoprids arrive later and bury themselves into the pile of excrement and effect all activities in situ. The fresh piles of excrement will house the adults while the drier piles contain eggs.

And the kleptocoprids are like cuckoos because they lay their eggs in a ball that has already been formed and is being rolled away by its unsuspecting owner.

Whatever method they employ, the environmental benefits of the presence of dung beetles is most notable. Paracoprid dung beetles are released together with cattle or goats in rehabilitation projects in old open-cast mines in South Africa to help with aeration of the soil and with water absorption. A single beetle can bury more than 1000 times its own body weight of excrement in 24 hours. The burying of cattle droppings returns 90% of feacal nitrogen to the soil in the summer. Interestingly, termites fulfill this function in the winter time when the dung beetles are inactive. It has also been found that uptake of the essential minerals, nitrogen, phosphorus and Sulphur in plants was 80% greater in soils where dung beetles were active. 

One look at the spatula-shaped head and the spines at the end of the tibia of this dung beetle show that it has been very busy digging. The ability of dung beetles to dig into very hard, dry soils to bury their collected dung, makes them ideal candidates for environmental rehabilitation projects.

They are also very important in the control of fly populations. Here's an interesting story about Australia and dung beetles:

Modern man arrived on the huge island of Australia around 40 000 years ago to find it filled with strange animals, big and small, of marsupial persuasion. Within 10 000 years almost all of the larger animals were wiped out by this invasion of human beings together with the larger species of dung beetle that cleaned up their mess, leaving only the smaller dung beetle species that utilised the droppings of Kangaroos and Wombats. 

This huge, up to 40mm in length, female Rhino beetle, Heliocopris hamadryas, is the only species of dung beetle that specialises in the excrement piles of large pachyderms like elephants and rhinos that can adapt to handling droppings of smaller herbivores. The other specialists of pachyderm dung would have become extinct together with their food producing hosts in the Finsbury mountains. This species is also able to emit a screeching sound when it is handled, a result of stridulating their thorax against their elytra. 

Then, very much later, in the 1800s, man introduced cattle onto this massive island. A single steed produces at least 12 piles of excrement a day. Although the grass surrounding these patties tends to go greener, it is unpalatable to further cattle grazing and thus is not utilised. Australia was losing around 200 000 hectares of grazing land to this every year. To add to this, these patties were optimum breeding sites for flies and parasitic worms. Roughly 3000 flies can breed from one cow's patty in a period of 2 weeks! In fact, prior to the successful introduction of dung beetles from South Africa, Bush flies, Musca vetustissima, were so problematic that it was illegal for restaurants and cafés in Australia to offer outside dining unless a designated area was enclosed by fly-wire.

In 1968, Dr Bornemissza, an entomologist and ecologist, introduced dung beetles, originally from Hawaii and then from South Africa, into the cattle lands of Australia. The beetles spread 50 - 80 km per season so by mid 1970, they were established over an area of approximately 400 square kilometers, including 2 islands, 10km and 30km offshore respectively. Ultimately, 29 species, out of 85, were successfully introduced into the country. The project is still ongoing to this day.

This photo of a Spider Dung beetle, Sysiphus sp, taken on the slopes of the Steenkamp's valley, clearly shows the club-tipped antennae that is divided into 3 segments, a feature unique to Dung Beetles from the Scarabinae subfamily.

 

This photo of a dung beetle, probably from the Heteronitis genus, shows the distinct shape of the front legs, flattened like a spatula for the smoothing down of the dung balls, and the spikes at the end to help the beetle to dig into hard ground. These dung beetles prefer the dung of hindgut fermenters, like Zebra and Warthog droppings on the estate.

On quite a few occasions I have spotted dung beetles rolling living and dead millipedes along the ground. According to my research, there are a couple of species in the Sceliages genus that are predators and scavengers of millipedes. They can detect the scent of the defense allomones excreted by millipedes when they are molested by predators or trampled by larger animals. The beetle will then roll the millipede to a suitable place and then straddle it and use its modified forelegs to disarticulate it into sizable chunks to bury. There have been many records of these Dung beetles stealing millipede prey from the Millipede Assasin, Ectrichodia crux, from the Reduviidae (see Jolly Season 2018 blog) 

A Spider Dung Beetle, Sysiphus sp, molding a ball of dung from an Eland dropping high above Finsbury House. Unlike all other dung beetles that roll their ball with their hindlegs, these Spider dung beetles do so with their forelegs (They obviously don't mind the smell as much, Har Har!). Some species of Sysiphus hang their ball on vegetation instead of burying it.

A common species on the estate, Scarabaeus rusticus, preparing a ball from a Civet dropping. Although the beetles prefer herbivore droppings, they will also feed at carcasses, the excrement of carnivores and from omnivores like the Civet.

A few interesting facts about dung beetles:

•  A dung beetle was recorded pushing a ball 1141 times it's own body weight, making it the strongest animal on the planet. That's equivalent to an average sized human pushing 6 fully laden double-dekker buses down the road!
•  Most dung beetle species live up to 3 years of age.
•  When the ground is very hot, dung beetles stand on top of their ball to allow their feet to cool down.
•  One South African species, Onthophagus gazella, navigates at night, using the milky way for direction finding. The only known animal to do this. Most dung beetles use the sun or moon for navigation.
•  A whole array of mite species use dung beetles as transport between dung patties as they cannot fly themselves.
•  Burrowing owls in the Americas use dung to attract dung beetles which they prey upon.
•  Ancient Egyptians worshipped dung beetles as their god, Khepri, the god of the rising sun who renewed the sun each day and rolled it across the sky.

Well folks, again I wish you all the best there in your homes. This virus thing is getting a little long in the tooth now and I wish, together with about 7 billion others, that it would end already! Good luck!