OVER the past few months a program to increase dung beetle numbers in Tasmania’s grazing regions has been underway.
A monitoring and redistribution program run by Cradle Coast Authority Natural Resource Management is aiming to help re-establish dung beetles in areas where numbers have declined.
Peak activity for the Blue Bomber or Geotrupes spiniger tunnelling dung beetles has come and gone for this year.
While there are still a few late emerging beetles flying at dawn and dusk, the advent of cooler weather, particularly night time minimum temperatures, has heralded their retreat for the wetter months.
From monitoring their numbers at one site near Ridgley in North-West Tasmania from December 2022 through to late April this year, emergence of G. spiniger in summer appeared to be a few weeks later than usual, which resulted in them persevering a little later into autumn.
Slightly cooler than average temperatures through November and December last year likely played a role in this, as larval development of beetles in the soil profile is in part driven by soil temperatures.
A program by the Cradle Coast Authority NRM around the region is aiming to identify grazing districts where this vigorous species of tunnelling dung beetle has declined in numbers over the years.
Reasons for declining beetle numbers could include successive hot and dry summers, low livestock numbers for a period, or inadvertent synchronised drenching across a district.
While G. spiniger are voracious tunnelling machines, soil becomes harder as it dries and there are limits to what beetles can tunnel through.
Because of this, irrigated dairy or beef farms are considered strongholds for this species through dry years.
Without ruminant livestock dung as a source of food, beetle numbers will also decline.
Monitoring beetle numbers allows trapping of beetles for redistribution to districts where numbers have fallen.
Through summer and autumn this year Cradle Coast NRM trapped and relocated around 20,000 Blue Bombers to various districts in Tasmania.
Some were rehomed at a dairy and cheesemaking operation in the Huon Valley in southern Tasmania, while around 8000 were released at grazing properties in Lorinna in the North West in January.
From working with Greenham Tasmania, the beef-producing district of Redpa was identified as having low numbers of Blue Bombers.
During late March approximately 8000 beetles were released at Redpa on three farms to improve the population over the coming years.
The Cradle Coast NRM team are also attempting to breed a winter-active species Bubas bison, which will be released across grazing farms in the region if successful.
For more information on tunnelling dung beetles please contact Cradle Coast Authority Regional Agriculture Landcare Facilitator Tom O’Malley at tomalley@cradlecoast.com