Creating entrances to tree cavities attracts hollow‐dependent fauna: proof of concept

Abstract

Redressing the paucity of tree hollows is essential for conservation of hollow‐dependent fauna in many landscapes around the world. We describe a method of accelerating availability of natural hollows in regenerating landscapes by mechanically creating entrances in tree stems that have existing voids or internal decay but have not yet developed entrances. We trialed this method in woodland and forest of south‐eastern Australia in 39 stems in the closely related tree genera Eucalyptus and Angophora. Exploratory drilling of 10‐mm diameter holes was used to detect the presence of internal decay or voids. We then drilled 40‐, 65‐, or 90‐mm diameter entrance holes, depending on the size of the potential cavity, 2.4–4.8 m above ground level. Camera traps showed that drilled entrances were investigated or used within hours of creation. A diverse suite of invertebrates, reptiles, mammals, and birds were recorded entering or leaving entrances, including threatened species. All 39 holes were used by animals with up to six vertebrate taxa using some entrances. Two bird species excavated material from within cavities, and three species of marsupial were recorded taking nesting material into the cavities. This trial provides evidence that adding entrances to currently inaccessible internal cavities in trees has potential to accelerate development of habitat for hollow‐dependent fauna, particularly in regenerating vegetation.

Tree hollow decline in new forest reserves with a long history of logging

“…In the short term, artificial nesting boxes may supplement hollow availability in some forest stands. However, they have different thermal properties (Ellis et al., 2022), can be exploited by predators of target species (Stojanovic, Owens, et al., 2021), and are not a realistic long‐term solution for hollow‐provision (Gibbons & Lindenmayer, 1996). A more promising approach for increasing hollow densities is the mechanical drilling of access holes in hollow trunks and limbs.…”

“…A more promising approach for increasing hollow densities is the mechanical drilling of access holes in hollow trunks and limbs. These constructed hollows can have similar thermal qualities to naturally occurring hollows and will likely persist for many years (Ellis et al., 2022; Griffiths et al., 2018).…”

Thermal Profiles of Chainsaw Hollows and Natural Hollows during Extreme Heat Events

“…An additional technique for constructing hollows is to use drills to mechanically create entrances in live trees with internal decay or hidden voids which have not developed entrances. A recent study showed that such hollows were rapidly used by wildlife, and temperatures inside the hollows fluctuated by 4 °C in summer whereas ambient temperatures fluctuated by 21 °C [ 52 ]. Hollows created with drills and auger bits may therefore be useful for creating artificial hollows, particularly if the aim is to create small hollows for smaller hollow-dependent animals such as microbats.…”