elop the hollows using instruments such as their beak, teeth or claws. The size of hollows may depend on the age of the tree. For example, eucalypts develop hollows at all ages, but only from when the trees are 120 ye

ars old do they form hollows suitable for vertebrates, and it may take 220 years for hollows suitable for larger species to form. Hollows in fallen timber are also very important for an

imals such as echidnas, numbats, chuditch and many reptiles. In streams, hollow logs may be important to aquatic animals for shelter and egg attachment. Hollows are an important habitat for many wildlife species, especially where the use of hollows is obligate, as this means no other resource would be a fea

sible substitute. Animals may use hollows as diurnal or nocturnal shelter sites, as well as for rearing young, feeding, thermoregulation, and to facilitate ranging behaviour and dispersal. While use may also be opportunistic, rather than obligate, it may be difficult to determine the nature of a species' relationship to hollows—it may vary across a species' range, or depend on climatic conditions. Animals will select a hollow based on factors including entrance size and shape, depth, and degree of insulation. Such factors greatly affect the frequency and seasonality of hollow use. Especially in Europe, entomologists are interested in the use of hollo