Diurnal and nocturnal tree species selection by koalas demonstrates individual preferences in a peri-urban landscape

Abstract

In New South Wales, legislation governing land clearing and development as it relates to koala conservation acts to prevent the destruction of habitat containing key tree species used by koalas. The identification of these key tree species is therefore critical to koala conservation. We aimed to compile a list of tree species used by koalas within the Wollondilly Shire region and investigate tree-use preferences. We radio-collared one female and four male koalas and tracked their movements over a period of 107–195 days. We conducted surveys within each koala’s home range to quantify the relative availability of each tree species, which we compared with their relative frequency of use. Koalas used 19 different tree species (17 during day, 12 during night), despite over 32 species being available. Eight species were preferentially used by one or more koalas; these were Eucalyptuts bosistoana, E. longifolia, E. puncata, E. crebra, E. globoidea, E. pilularis, E. tereticornis and Angophora floribunda. Two species were avoided: Corymbia gummifera and Acacia decurrens. Koalas consistently used larger trees relative to their availability, and we found a general but non-significant trend towards the use of larger trees at night compared with during the day. To achieve koala conservation, it will be necessary to preserve habitat patches comprising a diverse mixture of tree species and sizes, particularly trees >35 cm diameter at breast height (DBH), and to appropriately revegetate land with these criteria in mind.