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Implosion of warrens

In many areas of Australia, rabbits depend on warrens for shelter from climatic extremes, predator avoidance and also for successful breeding. ... Since rabbits do not readily dig new warrens, rabbit populations do not persist in areas where warrens are effectively destroyed and re-colonisation is made less likely.

Destruction of warrens can be done by someone with a spade or, at the other extreme, by a huge excavator/grader. In between, implosion is proving effective, neater in some locations, and sometimes possible when otherwise access for warren destruction is difficult. It can also be more economic where there is a lot of work to do - for example where neighbours are working together.

Correct blasting does not leave any craters, but lifts the subsoil and drops it back into place compressing the warren system in the process. This can even happen when small trees are over the top of the warren.

Ammonium nitrate mixed with fuel oil (ANFO) is the most commonly used explosive for warren destruction. Explosives are extremely hazardous and should only be used by suitably qualified and accredited operators.

Blasting is relatively expensive; however it does provide long-term control.
It has a greater effect on more moist and heavier soils, as gases are less able to escape through the subsoil.

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Two methods of implosion

Borehole method

Involves inserting charges into holes strategically bored across the warren.
With this method the force of the explosion is well below ground and there is limited disturbance to the surface. This gives a better collapse of the warren and reduced the likelihood of forming craters.
Holes are bored using a 50mm diameter auger. The best depth and spacing for borehole charging will depend on warren depth, soil type and amount and type of surrounding vegetation.

Burrow entrance method

Involves inserting charges down burrow entrances.
Recommended for deep burrows (>1 metre deep) or in situations where holes cannot be augured easily for the borehole method.
This method is more likely to lead to the formation of craters, which may cause erosion and could encourage re-colonisation by rabbits.
The charges are positioned as far down the burrow as possible, using a shovel handle or a long stick.

For more info see https://pestsmart.org.au/toolkit-resource/rabbit-warren-destruction-using-explosives/
and
https://www.agric.wa.gov.au/mechanical-physical-and-cultural/rabbit-warren-and-harbourage-destruction

For a video showing a simple way to destroy a warren, see:

Ripping

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NSW RABCOP: Rabbit Code of Practice and Standard Operating Procedures
54 | NSW Department of Primary Industries, March 2022


• Ripping is best suited to large-scale operations. However, it may not be suitable in the following situations:


⭕ where locations are inaccessible to available equipment, e.g., on steep slopes, very rocky land, along fences or riverbanks, around trees
⭕ where rabbits inhabit scrub with few warrens
⭕ when there is a risk of soil erosion or damage to conservation areas.

 

For more detail, see:

https://pestsmart.org.au/toolkit-resource/overview-of-rabbit-warren-and-harbour-destruction/
and
https://www.dpi.nsw.gov.au/__data/assets/pdf_file/0005/1396742/NSWRAB-SOP5-Rabbit-warren-destruction-by-ripping.PDF

For videos, see:

Comparison of cost:

Ripping can be done with a small, possibly hired, excavator where there is suitable access. Implosions should only be done where they are appropriate to the problem. The cost of both porocedures should be checked and the long-term benefits factored in when making a choice.