The use of habitat components as a predictor of population density of the bridled nailtail wallaby, Onychogalea fraenata (Gould, 1841)

 The Bridled Nailtail Wallaby, Onychogalea fraenata, was once widespread throughout eastern and south-eastern Australia, but is now found primarily at Taunton National Park (Scientific). With a population reduced to fewer than 500 individuals, survival of the species is dependent on the sustainability of suitable habitat in the present, and its continued availability in the long-term. 

While dietary selection and habitat utilisation have been investigated, the interrelationships between nailtail habitat components have not been examined. This study was conducted to address that issue. The aim was to develop a method of predicting nailtail populations in diverse habitats, with the ultimate goal being the identification of habitat conducive to continued nailtail survival. 

Data were gathered from six sites on Taunton National Park. Two sites corresponded to each of the following categories: low, medium and high nailtail population levels. These sites were examined to determine trends or patterns resulting in significant correlations between nailtail density and the floristic and shelter components. Components were found to fall within two basic habitat types: one favourable and the other unfavourable to the nailtail. 

In the favourable "Acacia habitat," interrelated floristic components consisted of Acacia trees and shrubs, Capparis, Opuntia, Schlerolaena and Parsonsia herbs, Capparis, Schlerolaena and Carissa shrubs, and Cenchrus, Cyperus, Paspalidium  and Sporobolus grass. Shelter components were comprised of Solid Logs, combined Solid Log -Hollow Log, combined Solid Log -Hollow Log -Woodpile, Shrub and combined Brigalow Regrowth -Shrub. 

In the unfavourable "gum -tree habitat", floristic components consisted of Eucalyptus, Cotymbia and Grevillea trees, Alphitonia, Eucalyptus, Grewia, Sida and Phyllanthus shrubs, Euphorbia, Cheilanthes and Hybanthus herbs, and Aristida, Eragrostis and Eriachne grass. Shelter components consisted of Trees, and variations of tree shelters to include Fallen Tree Crown, combined Tree -Live Tree Crown, combined Tree -Live Tree Root, and combined Tree -Live Tree Crown -Live Tree Root. 

To validate these proposed habitats, three additional study sites were selected on the Pine Grove, Red Rock Park and Rockview cattle properties adjacent to Taunton National Park. Based on habitat composition at these sites, the Pine Grove site was determined to be a low -to -medium nailtail density site; Red Rock Park a low -to - medium nailtail density site with the potential to support a high density of nailtails; and Rockview a medium nailtail density site. 

Based on the results of this study it is recommended that management of existing nailtail habitat incorporate the balanced mix of habitat components noted in the "Acacia habitat" while controlling the spread of "gum -tree habitat" components. Emphasis on floristic and shelter interrelationships is also considered essential in the establishment of future nailtail populations.