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Behaviour & communication

The effects of tooth wear on the activity patterns of free-ranging koalas (Phascolarctos cinereus Goldfuss)

Logan, M & Sanson, GD 2002, Australian Journal of Zoology, vol. 50, pp. 281–292.

This study found that increased tooth wear affects adult koalas in multiple ways. Koalas with significant tooth wear spend less time sleeping and being inactive than those without. They also spend less time moving about and stay within smaller areas. On the other hand, they spend more time feeding and have more spaced out feeding times, thus becoming less nocturnal.

  Tooth wear, as a result of biting forces and abrasion from Eucalyptus leaves, can cause changes in digestion rate and hence reduce the amount of nutrient and energy absorbed. To combat this, koalas with significant tooth wear appear to increase the amount of food they eat and also spend more time eating overall. As a result, koalas with significant tooth wear spend less time on other activities. For example, severe tooth wear is linked to a reduction in koala movement, and hence koalas with significant tooth wear have a smaller home range of around one-tenth that of other adults with less tooth wear. Although koalas are known to sleep in the day and spend more time feeding and moving at night, koalas with increased tooth wear appear to spend less time sleeping and being inactive in the day. Tooth wear thus appears to cause a shift in feeding pattern, where the amount of time spent feeding in the day and the night become similar. A reduction in daily inactivity can result in a significant reduction in amount of energy conserved, resulting in a further reduction in the amount of energy available for other essential activities.

  One of the reasons koalas move between trees is for social interaction. Movement between trees consumes large amounts of energy for koalas and, therefore, the koalas with high tooth wear were found to engage in fewer social interactions possibly due to having less time and energy available for expenditure. One of the implications of reduced socialisation is a potential decrease in reproductive opportunities and rate. In addition, nocturnality is thought to help koalas avoid predators and extreme daytime temperatures; thus, an implication of reduced nocturnality as a result of increased night-time feeding may be greater exposure to danger.

  While the authors of this study recognise that its results come from only six individuals studied, they assert that the findings are significant as they align with findings from other studies. The results of this study contribute to our understandings of the biological processes that affect koalas at the individual and population levels.


Summarised by Millie Thng


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