Research Trials

Around $600,000 has been invested in research to address questions raised about the introduction of dung beetles, since the Environmental Risk Management Authority (ERMA, now Environmental Protection Authority, EPA) granted approval for the importation and release of 11 species in February 2011.

This is a brief summary of the findings of the four most recent research projects. This research was presented to the Technical Advisory Group (TAG), established to advise the Dung Beetle Release Strategy Group (DBRSG), in September 2013.

 

The release of exotic pastoral dung beetles in New Zealand – a health risk assessment

In March 2013, the Ministry of Health commissioned the Institute of Environmental Science and Research (ESR) to undertake a human health risk assessment.

Among the conclusions from the 101-page report:

“Essentially our findings agree with the public health adage that it is better to bury faeces than leave them on the surface.”

“We consider that, in areas where dung beetles become abundant, their activity will decrease the transport of pathogens from ruminant dung on pasture, to people. There may be a relative increase in the risk of transmission from contaminated groundwater sources in these areas, if the groundwater sources are already vulnerable to contamination and drinking water supplies are not treated.”

“Over time as soil depth increases with dung beetle activity, this increase may reverse. The potential increase of transport to groundwater is likely to have a lesser effect than the potential benefit of decreased transport to surface waters.”

The authors concluded: “We did not see any need to undertake further research before the release of the dung beetles.”

The full report can be downloaded from the ESR website.

The impact of tunnelling and dung burial by new exotic dung beetles on surface run-off, survivorship of a cattle helminth, and pasture foliage biomass in New Zealand pastures.

Landcare Research established caged field trials to try to determine:

1) Whether dung beetle activity would reduce surface run-off and the amount of sediment suspended in the run-off;

2) Whether dung beetle activity would reduce the numbers of the infective larvae of a gastrointestinal parasite (nematodes) on pasture foliage, and hence potential infection rates of livestock;

3) Whether the processing and burial of dung by beetles resulted in an increase in above-ground pasture biomass available for stock to graze.

Results for the respective studies showed:

1) Large reductions in run-off volume in the presence of dung beetles, and reduction in sediment load in a high rainfall simulation.

2) Nematode numbers were significantly reduced in the presence of dung beetles, although this effect was not apparent at one of the three field sites (where there was no significant difference, which is likely due to the sandy soils at this site in conjunction with variable weather conditions).

3) There were no significant differences in the biomass of pasture foliage between the dung+beetles and dung-only treatments over this 84-day trial. This result is likely to be due to the time of year, drought conditions and length of time that the trials were run for.

The full paper can be viewed here.

 

What is the effect of dung beetles on gastrointestinal nematodes of stock?

Landcare Research undertook an extensive review of international studies that have examined the effect of dung beetles on gastrointestinal nematodes of stock. Overseas studies generally show that the action of dung beetles reduces the numbers of infective larvae of these nematodes on pasture. Although many overseas studies were conducted in warmer climates than are typical in New Zealand, some at least were comparable to climates in summer in more northern parts of this country. Rainfall in the overseas trials was often at a comparable level to parts of New Zealand. This suggests that overseas research is relevant for predicting the effects of dung beetles on nematodes in this country. Overall in most weather conditions/regions of New Zealand dung beetle activity will either reduce (or make little difference to) infective larval nematode numbers available to re-infect stock.

The full paper can be viewed here.

 

The possibility of brushtail possums foraging on exotic pastoral dung beetles in New Zealand.

This study was in response to concerns that dung beetles could become a food source for brushtail possums, which spread bovine tuberculosis (TB). If possums were drawn from the bush to pasture this could increase the transmission of TB to cattle and deer. Landcare Research examined the gut contents of 30 possums trapped in Northland bush adjacent to pastures with abundant populations of the already established Mexican dung beetle. No dung beetles were found in the dissected possum guts despite the presence of high levels of grass, which indicated the possums were spending time feeding in the pastures adjacent to where they were caught.

The full paper can be viewed here.

 

Peer review of Landcare Research reporting process to ERMA.

Landcare Research, the science provider for the DBRSG, arranged for an external peer-review of the process that led to ERMA’s approval for release of the dung beetles, as well as various animal disease issues. These external reviews supported Landcare Research’s approach and the quality of its science.

 

Next steps

The discussions from the TAG (with representatives from a wide range of organisations with an interest in dung beetles and the primary production industry) meeting have now been presented to the DBRSG committee. We are now working with our science provider, Landcare Research, to develop a release strategy, monitoring and on-going research programme. These details will be provided to the farming community as quickly as possible.

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