Choice of monitoring method can influence estimates of usage of artificial hollows by vertebrate fauna

ABSTRACT The loss of hollow-bearing trees is a key threat for many hollow-dependent taxa. Nesting boxes have been widely used to offset tree hollow loss, but they have high rates of attrition, and, often, low rates of usage by target species. To counter these problems, chainsaw carved hollows (artificial cavities cut into trees) have become a popular alternative, yet little research has been published on their effectiveness. We examined the usage of 150 chainsaw carved hollows by cavity-dependent fauna in the central west of New South Wales using observations from traditional inspection methods and remote cameras. Between October 2017 and April 2019, we detected 21 species of vertebrates (two reptile, one amphibian, 10 bird, and eight mammal species) inside chainsaw carved hollows, but the number of species detected was dependent on the chosen monitoring method. We detected six species inside hollows during physical inspections, whereas remote cameras detected 21 species entering hollows. Cameras detected eight species using hollows as breeding sites, whereas physical inspections detected just four species. Cameras detected two threatened mammals (squirrel glider (Petaurus norfolcensis) and greater glider (Petauroides volans)) raising young inside hollows, yet we failed to detect these species during physical inspections. For birds, the two methods yielded equivalent results for detection of breeding events. Overall, our study showed that few cavity-dependent species used chainsaw carved hollows as breeding sites. This highlights how artificial hollows are not a substitute for retaining naturally occurring hollows in large trees and revegetation programs.