Document ID: chunk:federal_register_of_legislation:F2022L00555:body:0:p80
Version: federal_register_of_legislation:F2022L00555
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Character Range: 246869–249731

to refugial areas (Seabrook et al. 2011). Natural migration away from climate-affected areas cannot be relied upon as a rescue for at-risk Koala populations.

28. Foraging ecology
Koalas are recorded to feed on more than 120 species of Eucalyptus, Corymbia and Angophora (Moore and Foley 2000; OEH 2018a; Phillips 1990), primarily the subgenus Symphyomyrtus (Moore and Foley 2005), and a few other genera (Marsh et al. 2014; Moore and Foley 2000; Phillips 1990). As the tree species composition differs between location so does the diet. Knowledge of feeding species is growing as new habitat locations are studied. It is the nutritional quality of the available trees, not the diversity of trees per se, that primarily drives foraging decisions and subsequently population density (Brice et al. 2019; Moore and Foley 2000; Sluiter et al. 2002). Generally, their preferred tree species in the south of their distribution include Manna Gum (E. viminalis), Swamp Gum (E. ovata) and Blue Gum (E. globulus), while in the north Tallowwood (E. microcorys), Red Gums (E. camaldulensis and E. tereticornis) and Grey Gums (E. puncutata and E. propinqua) are important (Van Dyck and Strachan 2008). The browse species consumed, and the proportion of diet made up by each species, varies considerably among populations and individuals (Moore and Foley 2005), and seasons (Davies et al. 2014; Ellis et al. 2013), even within the same home range (Blyton et al. 2019; McAlpine et al. 2008).
In a given area, Koalas browse tree preference, and the palatability of leaves, is determined by plant secondary metabolites (PSMs) and nutrient content. PSMs act as a herbivore deterrent (Gleadow and Woodrow 2002; Moore et al. 2004). PSMs are chemical compounds produced by the plant via metabolic pathways that are not used for primary processes (i.e. growth and reproduction). Nutritional quality refers to the foliar concentrations of digestible nitrogen, which is a proxy for protein and a key limiting nutrient for the Koala, and plant secondary metabolites that are known to influence palatability, feeding tree choice and subsequently population densities of the Koala. Dietary selection is thought to be driven by trade-offs between palatability and the nutritional value of leaves of digestible proteins within and between browse species (measured by available nitrogen or digestible nitrogen) (DeGabriel et al. 2008; Wallis et al. 2012) and concentrations of less desirable secondary plant metabolites including formylated phloroglucinol compounds (FPCs) and tannins (Au et al. 2013; Marsh et al. 2007; Stalenberg et al. 2014; Wallis et al. 2010). For example, FPCs are toxic and protect the plant from predators. FPC levels differ within a species, on an individual tree basis. Leaf moisture may play a role during times of low rainfall or heat stress (Ellis et al. 2010a).