How to dig a starter burrow
In May 2009 with the services of a local excavator operator and his excavator, we set forth to construct some release burrows for the wombats. We used a 450mm auger to dig the holes and then used a two-metre extension to extend the main hole. The biggest challenge was aligning the two holes – if the second hole was not at the appropriate angle it would go below or above the first tunnel. This happened with the first couple of burrows but after this the technique was refined and the remainder of the tunnels aligned perfectly.
We realised we were at the periphery of the deep sandy soil when digging the last burrow and the drilling become much slower as we reached a depth of about a metre. We had hit soil with increased clay content and decided to abandon the burrow due to the unsuitability of the soil for digging by the wombats.
On the next trip we will have to block the entrance that will not be used and also dig a number of starter burrows (shallow holes that will provide temporary shelter and could be the start of a real burrow.
DERM Burrow dug by a wombat. Photo: DERM
Burrow entrance (looking very much like a wombat-dug burrow!) with auger in second tunnel
Photo:
No doubt, the wombats will consider our burrows to be very amateurish but we hope the burrows will at least provide short-term shelter that they can modify or use until they dig their own burrows elsewhere.
Furnishing the release site for wombats
We need to provide shelter for the wombats in the form of release burrows providing them with refuge during the day, particularly for the first day. The design of the release burrows comes from measurements of natural wombat burrows including:
- Burrow angle: This varies markedly between different burrows constructed in different situations. The angle of about 30% has been selected to provide easy access for wombats and stability of the tunnel. Too shallow an angle would make the burrow more prone to collapsing while too steep an angle would not allow the animal the stability of footing to dig effectively.
- Burrow height and width: These were based on the dimensions of a sample of burrows – 450mm to 550mm high and 500mm to 600mm wide.
- Burrow Length: Research has shown that burrow conditions become more stable at 5 meters in length and very stable at 10 metres. It is not possible for us to dig a burrow of 10 metres long of the required height and width using available equipment but it is evident that we need to extend the burrow as far as possible. The longest burrow at Epping was 90 metres in length.
- Burrow Depth: One study of burrow architecture found the mean burrow depth to be 2.5 metres. It will not be possible to achieve this depth using available equipment and we will need to dig as deep as the equipment will allow.
Wombat burrows can be very long and they are not straight resulting in little or no light reaching the end of tunnels. Due to the lack of depth of our fabricated burrows, we thought it would be beneficial to have a bend in the burrow to reduce the amount of light reaching the end of the burrow. The plan was to dig one hole and then dig another perpendicular to the first and attempt to have the second hole meet the tunnel of the first.
Last updated: 10 September 2009