Murray Logan

The effect of tooth wear on the feeding behaviour of free‐ranging koalas (Phascolarctos cinereus, Goldfuss)

The free-ranging feeding behaviours of five adult koalas Phascolarctos cinereus with varying degrees of tooth wear were investigated using acoustically sensitive radio telemetry. An increase in tooth wear was found to be associated with a significant increase in the average amount of time spent feeding, average number of leaves consumed and the average number of daily chews. This suggests that koalas compensate for tooth wear by increasing food intake. Furthermore, there was a significant increase in the average number of chews per leaf and average chew rate, suggesting a greater investment in processing each leaf.

The association of tooth wear with sociality of free-ranging male koalas (Phascolarctos cinereus Goldfuss)

The sociality (as measured by the degree of bellowing and amount of tree use) of five adult male koalas and one sub-adult male koala (Phascolarctos cinereus), with varying degrees of tooth wear, were investigated using acoustically sensitive radio-telemetry. Initial increases in tooth wear that coincide with an increase in age to maturity were associated with an increase in reproductive effort. Advanced tooth wear was found to be associated with a decrease in reproductive effort. This trend in reproductive effort is consistent with life-history predictions, and suggests that tooth wear has the potential to impose limitations on the reproductive longevity and fecundity of free-ranging male koalas.

Evidence for the occurrence of rumination-like behaviour, or merycism, in the koala (Phascolarctos cinereus, Goldfuss)

This paper provides the first account of merycism in koalas (Phascolarctos cinereus), and in doing so, potentially sheds new light on the occurrence and significance of this behaviour in other herbivorous marsupials. Koalas fitted with acoustically sensitive transmitters, to monitor mastication and ingestive behaviour, were also found to make bouts of rhythmic ‘mastication-like’ noises that were not associated with ingestive feeding events. On average, these bouts consisted of 9.16 ‘mastications’, at an average rate of 1.21 ‘mastications’ per second, and occurred 53.3 times throughout a 24-h period. Furthermore, bouts were usually preceded by, and always followed by, a series of ‘creaky’, guttural noises that were interpreted as regurgitation and re-swallowing, respectively. Merycism may allow koalas to periodically re-masticate gastric digesta, while in a resting position, and thus potentially save energy and increase the extent of food preparation. Consequently, merycism may contribute to the koala’s ability to consume a high fibre, poor quality diet.

Ongoing effects of no-take marine reserves on commercially exploited coral trout populations on the Great Barrier Reef.

Networks of no-take marine reserves (NTMRs) are widely used for managing marine resources. Because they restrict fishing, managers need to monitor reserves to reassure stakeholders that they are achieving the intended results. In 2004, the Great Barrier Reef (GBR) Marine Park was rezoned and the area of NTMRs was greatly increased. Using manta tow we assessed the effectiveness of the new NTMRs in conserving coral trout (Plectropomus and Variola spp.), the principle targets of the GBR reef line fishery. Over a six year period, we sampled regional groups of matched pairs of similar reefs, ones closed to fishing under the rezoning and ones that remained open. Coral trout populations were significantly higher in NTMRs. While coral trout populations declined on reefs open to fishing, stocks were maintained in NTMRs, highlighting the ongoing benefits of marine reserves.

A new technique for measuring size distributions of fine ingesta/digesta particles

Techniques were developed to enable convenient, high-power image analysis of (ingested) food material. A constant volume of diluted gut sample was delivered to a large microscope slide before being slowly evaporated in still air to leave all particles statically on the same focal plane. Evaporation also allowed a meniscus to develop around each particle, forcing them to separate and thereby preventing overlap and aggregation of particles. Sub-samples were measured under four high-power magnifications (2050, 1290, 510 and 190) to permit precise estimates of size distributions of the very small particles. The techniques developed avoid the need for large ingesta/digesta samples, sieving, and filtering, all of which have limited previous studies.