What can a Hollowhog do?

The Hollowhog efficiently and safely creates large internal cavities through small entry holes in both living and dead wood. No other damage to the tree’s cambium (living tissue) occurs through the carving process meaning that there is little disruption to a tree’s growth.

The Hollowhog creates a 50 mm entry hole and then progressively carves a larger and larger hollow of any dimensions up to about 600mm wide and long by 600mm deep. The hollow shape can be easily adapted to the size and shape of the tree limb or trunk that it is being carved in.

As an example, this 300mm long by 200 mm wide by 350 mm deep hollow was carved through a 50 mm entry hole in less than half an hour.

The entry hole size and shape can be targeted to any fauna species through either carving a larger entry hole or adding entry modifiers to reduce the size back down to as small as needed. There are many reports of larger more aggressive species displacing smaller hollow occupants where a hollows entrance is big enough for them to get in.

It takes at least 70 to 120 years for hollows to form in trees in Australian forests. The Hollowhog forms these hollows in less than an hour, providing at least an additional 70 years of potential use by fauna and, most importantly, filling the gap until hollows are able to develop naturally.

For small entry holes, to ensure that the tree does not close it over in the first few growing season, and to provide weather protection on vertical trunks, the installation of an entry modifier can be a real benefit. The tree will readily lock in the attached modifier after about a year’s growth.

There are many variations to the size and shapes of hollows that can be achieved using the Hollowhog. The tool is just as efficient at making salvaged log hollows and habitat for ground dwelling fauna.

Is it safe to be carving into trees?

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This is by far the trickiest question to answer, but, as has been demonstrated over the past few years through the carving of hollows with chainsaws, if certain precautions are taken it can be made a safe process. The best advice will always be to seek professional advice from an arborist about what volume of the trunk or limb can be safely removed without compromising a tree’s structural stability. Research has been done in this area and professional advice from arborists, who have been installing chainsaw carved hollows as well as installers of Hollowhog hollows, should be consulted about how much of a limb or trunk’s diameter can be removed. As an example, this equates to a hollow with a diameter of about 200mm in a 600mm diameter tree. There are many trees that continue to live for decades with far less than 70 % of their trunk diameter remaining, but as hollow carving is a relatively recent development, err on the side of caution and always consult with a knowledgeable arborist for advice. There are now many arborists around Australia who have been installing chainsaw carved hollows.

Why not just use a chainsaw?

Chainsaw hollow carving has been happening now for the past few years and the hollows produced have been demonstrated to be used by fauna.

The process though requires that a face plate, that is longer and wider than the hollow, is cut off the tree to allow for hollow excavation to occur. In general, this means removal of anywhere up to a 500mm wide by 600 mm long plate of the tree’s living tissue for an average sized hollow. This plate is then glued and screwed back into place and a small entry hole cut for access, but the whole plate is now effectively dead wood. It can take many years for the plate to grow over in living trees, leaving it prone to splitting and cracking, rot, fire and termite attack. The good news is that trees do appear to continue to grow following chainsaw hollow carving.

By comparison, for an average sized hollow, the Hollowhog method leaves just the small 50mm entry hole and an intact surrounding living cambium. This means that it can be used in smaller diameter limbs than chainsaws including directly into the end of branch stubs and in any direction whether vertically up, down or anywhere in between. Arborists have been particularly keen on the Hollowhog’s safety aspects. There are no spinning parts outside the hollow entry after about 30 seconds of carving.

The Hollowhog also provides the ability to tap into existing natural voids in a tree. Many Eucalypts have central pipes that have no entry point. The Hollowhog can be used to form the entry point and carve out a space around the pipe to suit.


“It’s been a hugely satisfying project for everyone involved, with some saying that it was best thing they’d have ever done in their career!”

Matt Stephens, inventor