Magazine article Ecos

Time-Worn Koalas

Magazine article Ecos

Time-Worn Koalas

Article excerpt

ANY self-respecting koala needs good teeth. Koalas manage to survive on a diet of tough eucalyptus foliage that is low in protein and high in fibre, insect-repelling chemicals and toxins, but to digest this difficult diet the leaf material must first be thoroughly broken down. That's where the koala's impressive molars come into play.

Unfortunately for koalas, their initially immaculate teeth gradually wear down. Murray Logan and Professor Gordon Sanson, of Monash University, have been examining the consequences of this wear. They have reported that to maintain energy intake despite tooth wear, koalas have to increase food intake, spend more time feeding, and 'enhance chewing effort'.

Does this increased investment in feeding come at the expense of other activities? If a koala has to spend more time feeding to compensate for poor teeth, it may have less time and energy to expend on important social interactions and protecting food or other resources.

They investigated this by fitting koalas on Raymond Island (off Victoria) with acoustically sensitive radio collars and recording their activities at various times for 18 days. The koalas, all male, had various degrees of tooth wear.

The koalas with increased tooth wear spent significantly less time sleeping and inactive per 24-hour period. There was a 7.85% decrease in daily inactivity from about 20 hours to about 18.5 hours per day. It has been suggested that the extraordinarily low levels of activity (and low metabolic rates) in koalas, enough to put Homer Simpson to shame, enable them to conserve energy and hence set by on a poor high-fibre diet. …

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