Dung beetles offer many benefits to New Zealand farmers: better soils, pastures and waterways. Entomologist Dr Shaun Forgie, is a world expert on these extraordinary insects.
He breeds unusual livestock whose business is to eat the business of herbivorous mammals. He and his business partner Andrew Barber raise dung beetles at one of the world’s largest mass insect-rearing facilities, on a 3.2-acre block in Whenuapai.
Graduating from Auckland University with a BSc, Forgie began his science career as a technician with the Plant Protection group at DSIR, then at AgResearch, where he worked on the biological control of European and German wasps, and on sheep flystrike flies.
For reasons he cannot now recall, the lab had a fresh cow pat. To his surprise a native Australian dung beetle (long established in New Zealand) popped out of its centre, piquing his interest immediately, and setting him on a career focused on these industrious insects.
A man on a mission
Forgie began a Masters degree on the efficiency of this dung beetle in New Zealand pastures. It turned out to be ineffective on pasture, but made him realise that livestock farming in New Zealand would benefit greatly from a variety of efficient dung beetles that would sustainably manage the manure generated by introduced livestock.
In 1994 he moved to Africa where he completed doctorate research on ball-rolling scarabs (a type of dung beetle). Ever since, he’s been on a mission to develop a practical, sustainable solution to what he describes as New Zealand’s agricultural failure – allowing dung to be a waste and pollutant rather than a rich resource.
To achieve this, he needed to be able to introduce exotic dung beetle species. The process involved an application to the Environmental Protection Authority (EPA) that included rigorous risk assessment, cost-benefit analyses, and national iwi consultation. In 2011, with much assistance, he got the go-ahead to import 11 dung beetle species, and in 2014 Forgie and Barber launched Dung Beetle Innovations. Initially they worked from John Pearce’s Shelly Beach farm at the southern end of the Kaipara Harbour, but have operated from Whenuapai since 2018.
Waste or gold mine?
Dung is considered problematic in conventional farming practice, but it could be a gold mine with the help of dung beetles.
In the 1960s Australia’s CSIRO (government
science agency) was very progressive in allowing the importation of 51 dung
beetle species, 21 of which succeeded in establishing and are now active over
large areas of pasture. In Western Australia
it is estimated that dung beetles contribute up to a billion dollars per year
to the economy.
New Zealand has over nine million beef and dairy stock, each of which drops approximately ten cow pats a day. Most stock won’t feed within the radius of a cow pat equivalent to five times the size of the pat, because it’s repugnant to them. Dung is broken down by earthworms (also introduced) if they are present, and by degradation from sun and rainfall, but in pasture devoid of dung beetles, the cow pat can remain intact for a few weeks and up to a year, depending on the season.
That’s ninety million cow pats per day – about 85 million tonnes per year, with sheep, horses and alpacas contributing more than 14 million tonnes in addition.
Multiply that by five to allow for the foraging avoidance around each pat, and then multiply again by an average 30 days during which pasture is not grazed until the pats break down, and it’s easy to see the enormous ongoing pasture loss.
Enriching the soil
Non-degraded manure is a major source of contaminants that can end up in run-off and enter waterways.
Dung beetles alter this dramatically. As soon as a cow pat is dropped, the beetle’s extra-fine olfactory senses detect it and it flies to the new pat, where it immediately begins to burrow into the soil beneath the dung. It makes a series of tunnels, which it back-fills with either ball or sausage shapes (depending on the species) made from the manure to feed their larvae (grubs). Once the tunnels are filled the adult flies off to repeat the process on a fresh pile of manure.
Incubation of the developing stages of dung beetles can vary from six to eight weeks in smaller summer-active beetles, while larger ones incubate from six months to a year, even two years. After young beetles have hatched, half to two thirds of each dung ball or sausage remains in the ground for over two years, enriching the soil.
New Zealand has fifteen species of indigenous dung beetle, which inhabit native bush and forest. They are all flightless ball-rollers, opportunists who live on old carrion and the dung of animals such as weta, stick insects, geckoes, kauri snails, birds, possums, and even humans. They rarely leave their native forest habitats so aren’t much use for pastoral improvement.
Reducing gut parasites
“In New Zealand we drench our stock to protect them from gastrointestinal worms, including nematodes and various external pests,” says Dr Forgie. “Most conventional farmers rotate stock through pasture every 25 days or so depending on season and pasture condition. At certain times, gut parasites are evacuated from the cow’s digestive system through their dung.
“Nematodes hang out in the avoidance zone around manure, climbing up to the tallest grasses where they can survive up to 90 days, by which time the farmer will have rotated his stock maybe three times. In a dairy system this means the stock are highly likely to be re-infected and the cycle continues, necessitating drenching.
“When dung beetles are in play, the dung disappears in three to four days and nematode uptake is reduced by 76%, reducing reliance on drenching and allowing livestock to carry much lower worm burdens against which they can more easily build immunity.”
Soil and forage improvement
Dung beetle tunnels aerate the soil and improve its structure. By taking carbon- and nutrient-rich dung deep into the soil, grass, forage and crops are encouraged to establish deep drought-resistant roots with a source of food well below the dry zone. Microbial activity flourishes to the depths the dung has been buried.
Improved soil structure allows the rain to conduct surface components, including contaminants, down into the ground, reducing run-off by 80%. This alone makes dung beetles a valuable tool to improve the quality of water coming off farms.
Highly permeable soils are often unable to retain nutrients because they drain through into groundwater, but because dung beetles fill their tunnels, these types of soils also benefit from retained nutrients for crops and forage, and above ground a greater biomass of grasses, crops, and forage becomes available.
Increase in earthworms
Dr Forgie says a five-fold increase in earthworms can be expected in pasture with good dung beetle activity, and they’ll be as deep as 50 cm because the soil has become sufficiently permeable for them to reach that depth in pursuit of the dung left behind by beetles.
One Northland farmer who introduced three species in December 2018 reported that, while activity had died down temporarily over the winter, he was seeing dung beetle-shredded cow pats with lots of earthworms under them where previously there had been no worms.
Dung beetle tunnels vary in depth from 60–90 cm. Depth depends on the beetle species, and the quality of the ground, e.g. compact and clay pan soils are generally burrowed to around 45–50 cm, while highly permeable soils will be tunnelled to 90 cm or more.
With plentiful food supply, beetle colonies grow exponentially. By year two or three, noticeable activity will be occurring on pastures, and by year five, pasture improvement should be obvious. Colonies will reach saturation point nine years after being released. However, providing food is available, outlying beetles will continue to extend their range by a kilometre a year.
Beetle breeding and feeding
Dr Forgie and Andrew Barber currently breed eight of the 11 authorised species of dung beetle, and are planning to import the remaining three species in the near future. Each species is bred for specific seasons and conditions – some like cold conditions and others, dry.
At the Dung Beetle Innovations breeding facility Dr Forgie and four full-time and two part-time staff process 1500 kg of dung on an easy day, and when it’s busy, they’re shovelling shit at the rate of three tonnes a week. A local Taupaki dairy farm keeps them deep in it.
“They take a lot of feeding,” Dr Forgie says. “The beetles are very active when it’s hot and eat much more.”
Slow but steady growth
Experience with dung beetles from farmers in the field is still limited since it takes a few years to see the full range of benefits, and releases have only been occurring for three years, but some are already reporting positive results.
Dr Forgie feels frustrated by the slow uptake of, and interest in, dung beetles – especially given the comparatively small $3 million investment that would be required over 10 years to remediate much of New Zealand’s pasture land. However, interest in these beneficial beetles is definitely growing.
Dung beetles at a glance
- There are 5000 species of dung beetle globally.
- The most famous is the Egyptian scarab (a ball-roller that has no value on pastures).
- Modern dung beetle lineage is 35–50 million years old, but ancient fossil lineage can be traced to 98–144 million years.
- Dung beetle pasture species available in NZ: Onthophagus binodis, Onthophagus taurus, Digitonthophaus gazella, Geotrupes spiniger, Copris incertus, Bubas bison, Onitis alexis, Copris hispanus.
- Dung Beetle Initiative: dungbeetles.co.nz
Beetlemania (the blog): dungbeetles.co.nz/blog
©Theresa Sjöquist – freelance writer based in Helensville. www.theresasjoquist.com
First published in Organic NZ magazine – March/April 2020 Vol. 79 No.2