Domestic cattle drop 33 million tonnes of dung on Australian pastures every year. Pasture areas are reduced and fly pests, like the bushfly and the buffalo fly, thrive.
Entomologists are seeking a solution to these problems through the dung beetle, which breaks up and disperses dung pads.
Selected species of dung beetles imported from Africa are being mass bred in Australia for release in cattle breeding areas. Early results indicate that they will prove an outstanding example of biological control.
[Text appears: Dung Down Under. A study in biological control]
Narrator: In 1788, five cows, two bulls, 29 sheep, five rabbits and other assorted livestock were landed in Australia by the First Fleet.
[Image changes to show a dung beetle making and rolling balls of dung]
Of course there were the uninvited passengers too; fleas, lice and rats. But one special passenger was missing from the livestock consignment, the dung beetle. Because of this omission an ecological imbalance was caused which has lasted for nearly two centuries. This has left Australia with several pests and without the means to control them.
[Music plays and image changes to show herds of native African animals, elephants, buffalo and cattle]
To attempt to restore the balance scientists have turned to Africa.
[Image changes to show African dung beetles]
Many kinds of cattle evolved in Africa and along with them many types of dung beetles. Over millions of years a balance has been established between them.
The cattle drop dung; the beetles break up the dung pads and bury them as food for their young.
The beetle research program in South Africa is the brainchild of Dr George Bornemissza of the CSIRO’s Division of Entomology.
[Image changes to show Doctor George Bornemissza at a microscope in a laboratory]
Dr Bornemissza: Here in Africa the large herds of herbivorous animals support an immensely rich dung beetle fauna.
[Image changes to show a herd of African cattle with feeding calves]
Through millions of years dung beetles evolved amongst these herds of game to such diversity that south of the Sahara alone over 1,800 species are already known to science.
[Image changes back to shots of different species of African dung beetles]
It was therefore obvious that our attention had to be focused on this vast continent and its beetles.
The Division of Entomology of the CSIRO, in cooperation with the plant protection Research Institute of South Africa, established a station in Pretoria in September 1970 to serve as a base for a research project.
[Image changes to show an outside shot of the Dung Beetle Unit in Pretoria, South Africa]
We started our program by surveying various game parks of southern Africa. One of the many sanctuaries we visited was the Gorongosa National Park near Beira in Mozambique.
[Image changes to show two Researchers in the field surveying and collecting beetles accompanied by armed Rangers. A herd of elephants can be seen in the background]
One of the best ways to collect dung beetles is by trapping them in pitfall traps, baited with pieces of intestines of smaller animals.
[Image changes to show the Researchers checking the traps with a herd of buffalo in the background]
Special attention is being paid to the droppings of buffalo’s as the most compatible dung in shape, size and consistency with that of domestic cattle.
In my search for bovine dung beetles in Africa the most spectacular beetle I have found so far was on Gorongosa Ranch in Mozambique.
[Image changes to show a Researcher creating a dung pad from a plastic bag of manure]
On this ranch dung pats were exposed in a paddock to study the speed of dung burial, a crucial factor in the control of flies that breed in cattle dung. After 24 hours hardly a trace of dung was left.
[Camera zooms in on the space where the dung pad was set and only the clean soil and exit holes can be seen]
Only the churned soil with a few exit holes indicating that some of the beetles had already departed.
[Image changes to show Researchers preparing dung beetle eggs for export to Australia]
All the beetles that have been collected were taken into our laboratories, sorted out and paired off for performance studies and only the eggs of the most efficient species will get a flight ticket to Australia.
Narrator: Because of quarantine considerations, adult beetles cannot be sent to Australia. Instead after surface sterilisation in Africa, the eggs of selected beetles are consigned by air in specially designed containers.
[Music plays and image changes to show the arrival of the jet and egg parcel at Canberra airport]
Narrator: Through the approval of the quarantine authorities strict measures are in force to prevent the entry of any exotic parasites or diseases. The first generation of beetles bred from the imported eggs never leave the quarantine area and eggs laid by these beetles have to pass through a highly effective surface sterilisation process.
[Image changes to show the quarantine station and sterilisation process taking place]
Field releases of beetles are only made from later generations mass bred from these first generation African species.
The imported eggs must be provided with suitable breeding conditions. The dung beetle team set to work to roll handmade dung balls from local cattle dung.
[Image changes to show the imported eggs being placed in hand rolled dung balls for incubation]
As egg consignments may number up to fifteen hundred or more this can be a lengthy job.
Cavities made in the balls provide a suitable breeding chamber for the beetle eggs.
[Image changes to show eggs being placed into the hole of the dung ball]
The balls are packed in sand inside their incubation tubes and sprayed with water to ensure they retain a sufficient level of moisture. Except for the eggs, all imported materials is sterilised as a further precaution that nothing undesirable is introduced.
[Image changes to show the Researcher sterilising the equipment]
From egg hatching to the emergence of the adult beetle may take between four and eight weeks depending on the beetle type.
[Image changes to show a Researcher reviewing the cages where the eggs are being kept]
Mass breeding of selected beetle species takes place under laboratory conditions to produce sufficient numbers for release in the field.
In the beetles so far introduced into Australia, two types of dung dispersal behaviour can be seen.
[Image changes to show a Researcher looking at dung beetles in a glass case as they’re tunnelling]
The first can be illustrated by the tunnelling beetle. This builds its nest directly beneath the dung pad. In order to film nesting activity, an artificial soil profile has been prepared in a sandwich of two pieces of glass. The beetles work in mated pairs.
[Camera zooms in on the dung beetles, which can be seen tunnelling]
With amazing vigour and determination the female excavates tunnels in the soil. Pushing soil to the surface in front of her with the bulldozer action. She constructs the egg chambers or brood balls from dung material which has been pushed into the tunnels by the male. In warm soil the beetles work rapidly, building a brood ball about every two hours. After egg-laying the female seals of the entrance to the ball.
[Camera zooms in on the chamber where the larva can be seen]
The larva hatches after about three days and starts feeding on the brood ball. It eats the solid dung material as it has a well-developed biting and chewing mouth.
[Image changes to show a Scientist looking at a dung beetle specimen he’s holding under a magnifying glass. The camera zooms in on the mouth area of the beetle]
On the other hand, adaptation in the adult has produced highly specialized mouthparts, which are only capable of sucking the liquid components of the dung.
The young beetle passes through its pupal stage and after about thirty-five days emerges as a young adult to dig its way to the surface and migrate to new dung pads in the vicinity and begin the cycle again.
[Camera zooms in on the dung beetle as it emerges from the soil]
[Image changes to show a dung beetle making and rolling balls of dung]
The second type of dung dispersal behaviour is dung ball rolling. The ball rolling beetles disperse the dung by breaking off fragments and forming them into balls. There isn’t always honour among ball rollers and beetles may sometimes vie for possession of a ball. But the rightful owner usually manages to beat of the intruder.
With prodigious energy the ball rollers go about their work, often molding and manoeuvring lumps of dung far larger than themselves.
[Camera zooms in on a dung beetle moving a dung ball into place]
At the chosen nesting site the female climbs onto the ball and excavates a chamber. After a single egg has been laid, she seals off the cavity, raising a slight mound over the egg chamber.
[Camera zooms in on the dung ball where the mound can be seen]
[Image changes to show a paddock of dairy cattle around a dam]
The ecological imbalance, which resulted from the introduction of domestic livestock into Australia without suitable dung burying beetles, was not relieved by the naturally occurring beetle species.
[Image changes to show kangaroos in a bush setting]
These had adapted themselves to dispose of the smaller drier droppings of animals such as kangaroos and other marsupials.
[Camera zooms in on a dry, crumbly sample of animal droppings being handled]
The native beetles couldn’t deal effectively with the larger and wetter dung pads from domestic livestock.
[Image changes to show a domestic livestock dung being separated to reveal the pest fly larvae feeding]
This cattle dung is the chief breeding site for pest flies. The bush fly in temperate areas and the buffalo fly in topical areas.
[Image changes to show flies on dung pads in a temperature controlled insectory and the sound of them buzzing can be heard]
Studies carried out in temperature control-insectories have established that speed of dung burial by beetles is a critical factor in fly control.
[Image changes to show shots from the time-lapse comparison of dung beetle’s speed in burying dung pad beside control pad without beetles]
This time-lapse sequence, filmed over some forty-three hours, shows the activities of beetles in breaking up and burying a dung pad alongside a control pad where beetles are absent. If beetles are sufficiently numerous and active, a cow pad can be buried within the first 24 hours. At this rate of disposal, fly development in the dung will be severely restricted and the few flies produced will be stunted, short-lived and incapable of laying many eggs.
[Image changes to show collected fly samples, a comparison of fly breeding activities in a normal dung pad alongside a dung beetle buried pad]
On the left, fly reproduction has been normal in the pad where beetles were absent. While in this other dish, few have survived the burying activity of the beetles and those that have are small.
Another natural enemy to help control fly populations is the Histerid beetle. This is not a dung burying beetle but feeds directly on the fly larva in the dung pad.
[Image changes to show Histerid beetles feeding on fly larvae in a dung pad]
No dung pad adapted Histerids were known to exist in Australia, so this beetle species too had to be imported. Particularly after periods of lean food supplies, Histerids can show extraordinary enthusiasm for their work.
[Image changes to show a herd of cattle, the sound of them mooing can be heard]
North on the Tropic of Capricorn, dung pads are the breeding grounds for the buffalo fly.
This is a major pest of livestock in areas such as coastal Queensland, the Northern Territory and the Kimberley region of Western Australia.
[Image changes to show the Buffalo fly infestation on cattle]
Infestations can number thousands on one animal alone. In the past chemical sprays were used to control the buffalo fly but their use is now being restricted to avoid problems of chemical residues in animal products. A fly may bite an animal ten to 12 times a day. This causes extreme restlessness in cattle and can lead to sores around the animal’s eyes and lesions of the hide due to the beast’s efforts to relieve the irritation.
[Image changes to show a researcher inspecting a dung beetle dispersed dung pad]
The dung beetle can play a key role in tropical areas by dispersing the buffalo fly’s breeding sites. In heavily stocked cattle country dung lies around wastefully blanketing significant areas of pasture.
[Image changes to show cattle pasture without dung beetles showing effect of dung pads on grass growth. The camera zooms in on the ground where the grass is dry and patchy]
The amount of dung dropped by one animal in a year can smother and alienate up to one tenth of an acre of pasture and there are some 25 million cattle in Australia.
[Image changes to show cattle pasture where dung beetles are active. The camera zooms in on the ground where the grass is green and full]
Where the pads are left undisturbed a leaching of concentrated dung nutrients stimulates a rank fringe of grass growth, which is unpalatable to cattle and remains ungrazed.
[Image changes to show the researcher inspecting grass growth in soil where dung is buried. He then dig out a soil sample]
Where dung beetles are active this loss of pasture is avoided and pads are rapidly broken-down. Grass growth actually benefits from dung nutrients released and combined with the soil. In the long term the level of soil nutrients will rise with the continued burial of dung.
[Image changes to show samples, as described below]
Three soil samples are sown with Japanese millet seed. In the first pot the millet plants were grown in soil alone.
[Camera zooms in on the first sample of millet, labelled “No Dung” the plant is small and limp]
In the second, dung was allowed to remain undisturbed on the surface.
[Camera moves to the second sample of millet, labelled “Dung without beetles” the plant is taller and fuller]
While in the third, beetles were added and allowed to bury dung in the soil.
[Camera moves to the third sample of millet, labelled “Dung with beetles” the plant is much taller and very full]
Of course this was a laboratory experiment and in the field such dramatic variations in growth will rarely occur. However over a period of time dung beetle activity will substantially increase the availability of the dung nutrients for plant growth.
[Image changes to show Researchers working with different dung beetle species]
By studying beetle behaviour under comparable conditions of soil, climate and dung types in Africa and under laboratory trials in Australia, a scientist can select the most promising beetle species from the vast number available in Africa.
[Image changes to show a Researcher pinning different specimens of dung beetles onto a board where many more specimens are arranged]
Releases of dung beetles are being made progressively throughout the chief cattle areas of northern and southern Australia.
[Image changes to show Researchers in discussion beside a map of Australia on field release sites]
Field releases are made by officers of the CSIRO’s Division of Entomology, in cooperation with the state Departments of Agriculture, farmers and others with knowledge of the local situation.
[Image changes to show Researchers in discussion with farmer in country town on dung beetle release in the Yarra Glen area]
Release sites are selected where the particular beetle species is most likely to adapt best to the local conditions and multiply and spread rapidly.
Researcher: Well if you could give us a bit of an idea, Steve, as to where your property is and what paddocks we use?
Steve: Yes, the property is situated four miles north of Yarra Glen in the valley of the Steels Creek. A valley that consist of some 3,000 acres of land, much of it creek flats and rising hill country.
Researcher: And there are plenty of cattle in the area?
Steve: Yes, it’s a predominantly cattle area.
Narrator: Cooperation of graziers in selecting sites is readily offered and is vital to the success of the program.
[Image changes to show an Entomologist with a farmer at a release site on a farm property]
Aside from the presence of grazing animals, a major consideration in selecting release sites; a suitable climate and type of soil. The nature of the soil will affect the beetles’ ability to construct soil tunnels.
Areas that are subject to regular flooding should be avoided in making the initial releases because of the likelihood of beetles drowning.
[Image changes to show beetles being emptied onto dung pads]
It has taken us nearly two centuries to start putting the missing link back into the ecological chain. While there remain many unknown factors, which may affect the success of the beetle program, early results indicate that dung beetles will prove an outstanding example of biological control of immense value to Australia.
[Camera zooms in on the dung beetle tunnelling into the dung pad]
[Music plays and time-lapsed pictures of the dung pad being buried appear on screen]
[Credits: Photography in South Africa: Frans Conradie – National Film Board, South Africa. George Bornemissza – Division of Entomology CSIRO. In Australia: John Green & Roger Seccombe. Direction: Roger Seccombe. Production: Roger Seccombe, Stan Evans. A CSIRO Film – 1972]